Atmosphere

15 pages, 5132 KiB

Open AccessEditor’s ChoiceArticle

Real-Time Low-Cost Personal Monitoring for Exposure to PM_2.5 among Asthmatic Children: Opportunities and Challenges

by Dohyeong Kim, Yunjin Yum, Kevin George, Ji-Won Kwon, Woo Kyung Kim, Hey-Sung Baek, Dong In Suh, Hyeon-Jong Yang, Young Yoo, Jinho Yu, Dae Hyun Lim, Sung-Chul Seo and Dae Jin Song

Atmosphere 2021, 12(9), 1192; https://doi.org/10.3390/atmos12091192 - 15 Sep 2021

Cited by 2 | Viewed by 3220

Abstract

This study aims to evaluate the accuracy and effectiveness of real-time personal monitoring of exposure to PM concentrations using low-cost sensors, in comparison to conventional data collection method based on fixed stations. PM_2.5 data were measured every 5 min using a low-cost [...] Read more.

This study aims to evaluate the accuracy and effectiveness of real-time personal monitoring of exposure to PM concentrations using low-cost sensors, in comparison to conventional data collection method based on fixed stations. PM_2.5 data were measured every 5 min using a low-cost sensor attached to a bag carried by 47 asthmatic children living in the Seoul Metropolitan area between November 2019 and March 2020, along with the real-time GPS location, temperature, and humidity. The mobile sensor data were then matched with station-based hourly PM_2.5 data using the time and location. Despite some uncertainty and inaccuracy of the sensor data, similar temporal patterns were found between the two sources of PM_2.5 data on an aggregate level. However, average PM_2.5 concentrations via personal monitoring tended to be lower than those from the fixed stations, particularly when the subjects were indoors, during nighttime, and located farther from the fixed station. On an individual level, a substantial discrepancy is observed between the two PM_2.5 data sources while staying indoors. This study provides guidance to policymakers and researchers on improving the feasibility of personal monitoring via low-cost mobile sensors as an alternative or supplement to the conventional station-based monitoring. Full article

(This article belongs to the Special Issue The Potential Use of Low-Cost Air Pollution Sensors in Variety of Indoor and Outdoor Applications)

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14 pages, 924 KiB

Open AccessEditor’s ChoiceArticle

Winter Air Pollution and Genotoxic Effects in Children Living in a Highly Polluted Urban Area

by Claudia Zani, Elisabetta Ceretti, Donatella Feretti, Milena Villarini, Massimo Moretti, Marco Verani, Antonella De Donno, Sara Bonetta, Annamaria Buschini, Alberto Bonetti, Silvia Bonizzoni, Umberto Gelatti and on behalf of the MAPEC-LIFE Study Group

Atmosphere 2021, 12(9), 1191; https://doi.org/10.3390/atmos12091191 - 15 Sep 2021

Cited by 4 | Viewed by 2044

Abstract

Air pollutants, especially PM, have been found to determine various effects on human health, including genotoxic effects. The aim of this study was to assess DNA damage with micronuclei (MN) and comet tests on buccal cells of 6–8 years old children living in [...] Read more.

Air pollutants, especially PM, have been found to determine various effects on human health, including genotoxic effects. The aim of this study was to assess DNA damage with micronuclei (MN) and comet tests on buccal cells of 6–8 years old children living in an area with high air pollution. Both tests were repeated in the same children in two consecutive winters to compare the levels of DNA damage under different pollution conditions. A complete data set including lifestyle, air pollutants levels and biological sampling was available for 180 children in the two winters. A high mean MN frequency was found in both seasons, with higher value in the first (0.51 ± 0.59) than the second winter (0.40 ± 0.52), whereas DNA damage measured with comet test showed higher damage in the second versus the first winter (visual score 208.8 ± 67.1 vs. 173.2 ± 50.8). The associations between air pollutant levels (CO, NO₂, SO₂, benzene, O₃, PM_10, and PM_2.5; PM_0.5 and PAHs) and DNA damage were investigated at different lag times, and mainly, no significant association was found. This study on repeated measure of MN frequency and DNA damage in children’s buccal did not show an association with various air pollutants evaluated in an area with high levels of air pollution. Full article

(This article belongs to the Special Issue Outdoor Air Pollution and Human Health)

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15 pages, 1334 KiB

Open AccessEditor’s ChoiceArticle

Flux–Profile Relationships in the Stable Boundary Layer—A Critical Discussion

by Giampietro Casasanta, Roberto Sozzi, Igor Petenko and Stefania Argentini

Atmosphere 2021, 12(9), 1197; https://doi.org/10.3390/atmos12091197 - 15 Sep 2021

Cited by 2 | Viewed by 2410

Abstract

Flux–profile relationships are crucial for parametrizing surface fluxes of momentum and heat, that are of central relevance for applications such as climate modelling and weather forecast. Nevertheless, their functional forms are still under discussion, and a generally accepted formulation does not exist yet. [...] Read more.

Flux–profile relationships are crucial for parametrizing surface fluxes of momentum and heat, that are of central relevance for applications such as climate modelling and weather forecast. Nevertheless, their functional forms are still under discussion, and a generally accepted formulation does not exist yet. We reviewed the four main formulations proposed in the literature so far and assessed how they affect the theoretical behaviour of the kinematic heat flux (

H_{0}

) and the temperature scale (

T_{*}

) in the stable boundary layer, as well as their consequences on the existence of critical values for both the gradient and the flux Richardson numbers. None of them turned out to be fully consistent with the literature published so far, with two of them leading to very unreliable expressions for both

H_{0}

and

T_{*}

. All considered, a convincing description of flux–profile relationships still needs to be found and seems to represents a considerable challenge. Full article

(This article belongs to the Special Issue The Stable Boundary Layer: Observations and Modeling)

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10 pages, 274 KiB

Open AccessEditor’s ChoiceArticle

Exercise under Exposure to Air Pollution and Spirometry in Healthy Adults with and without Allergy

by Krzysztof Kocot, Kamil Barański, Edyta Melaniuk-Wolny, Eliwra Zajusz-Zubek and Małgorzata Kowalska

Atmosphere 2021, 12(9), 1168; https://doi.org/10.3390/atmos12091168 - 11 Sep 2021

Cited by 3 | Viewed by 1984

Abstract

Ambient air pollution is a major environmental threat to human health. The acute effects of exposure to ambient air pollution during physical exercise may depend on allergy status. The aim of the study was to assess the acute respiratory responses to air pollution [...] Read more.

Ambient air pollution is a major environmental threat to human health. The acute effects of exposure to ambient air pollution during physical exercise may depend on allergy status. The aim of the study was to assess the acute respiratory responses to air pollution exposure during physical training in young adults with and without allergies. The studied group included 71 healthy young adults (n = 16 with allergy and n = 55 without allergy). Students completed two indoor physical training trials lasting 45–60 min: when air pollutants concentrations were high (exposure trial) and low (control trial). During each trial, we monitored outdoor and indoor environmental conditions. Participants performed spirometry at baseline and directly after the exercise. Exercise during exposure trials led to a small decrease in the percentage of predicted forced expiratory volume in 1 s (FEV₁ ref). Only during the control trials did the FEV₁/forced vital capacity quotient (FEV₁/FVC) statistically significantly increase. Moreover, just in the allergy group, there were statistically significant negative correlations between post-exercise FEV₁/FVC change and 3 h average outdoor particulate matter with aerodynamic diameter <10 µm (PM₁₀) and nitrogen dioxide (NO₂) concentrations (PM₁₀: r = −0.54, p = 0.02, NO₂: r = −0.60, p = 0.02). In young and healthy adults, sports training under exposure to high levels of ambient air pollutants leads to a small decrease in FEV₁. The allergy might be a modifying factor in the respiratory responses to air pollution. Post-exercise decrease in FEV₁/FVC was related to pre-exercise 3 h averages of PM₁₀ and NO₂ only in people with ever-diagnosed upper-respiratory allergy. Full article

(This article belongs to the Special Issue Outdoor Air Pollution and Human Health)

18 pages, 10287 KiB

Open AccessEditor’s ChoiceArticle

Tropical Cyclone Formation within Strong Northeasterly Environments in the South China Sea

by Yung-Lan Lin, Hsu-Feng Teng, Yi-Huan Hsieh and Cheng-Shang Lee

Atmosphere 2021, 12(9), 1147; https://doi.org/10.3390/atmos12091147 - 5 Sep 2021

Cited by 2 | Viewed by 2437

Abstract

In the South China Sea (SCS), 17% of tropical cyclones (TCs) formed in the late season (November−January) were associated with a strong northeasterly monsoon. This study explores the effects of northeasterly strength on TC formation over the SCS. The Weather Research and Forecasting [...] Read more.

In the South China Sea (SCS), 17% of tropical cyclones (TCs) formed in the late season (November−January) were associated with a strong northeasterly monsoon. This study explores the effects of northeasterly strength on TC formation over the SCS. The Weather Research and Forecasting (WRF) model is used to simulate the disturbances that develop into TCs (formation cases) and those that do not (non-formation cases). Two formation (29W on 18 November 2001 and Vamei on 26 December 2001) and two non-formation (30 December 2002 and 9 January 2003) cases are simulated. To address the importance of upstream low-level northeasterly strength to TC formation, two types of sensitivity experiments are performed: formation cases with increased northeasterly flow and non-formation cases with decreased northeasterly flow. If the strength of the northeasterly is increased for the formation case, the stronger cold advection reduces the convective instability around the disturbance center, leading to the weakening of the simulated disturbance. If the strength of the northeasterly is decreased for the non-formation case, the simulated disturbance can develop further into a TC. In summary, strength of the upstream low-level northeasterly flow does affect the environmental conditions around the disturbance center, resulting in the change of TC formation probability over the SCS in the late season. Full article

(This article belongs to the Special Issue Asia-Pacific Region: Monsoons and Typhoons)

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18 pages, 9639 KiB

Open AccessEditor’s ChoiceArticle

Large Eddy Simulations of Turbulent and Buoyant Flows in Urban and Complex Terrain Areas Using the Aeolus Model

by Akshay A. Gowardhan, Dana L. McGuffin, Donald D. Lucas, Stephanie J. Neuscamman, Otto Alvarez and Lee G. Glascoe

Atmosphere 2021, 12(9), 1107; https://doi.org/10.3390/atmos12091107 - 27 Aug 2021

Cited by 8 | Viewed by 3647

Abstract

Fast and accurate predictions of the flow and transport of materials in urban and complex terrain areas are challenging because of the heterogeneity of buildings and land features of different shapes and sizes connected by canyons and channels, which results in complex patterns [...] Read more.

Fast and accurate predictions of the flow and transport of materials in urban and complex terrain areas are challenging because of the heterogeneity of buildings and land features of different shapes and sizes connected by canyons and channels, which results in complex patterns of turbulence that can enhance material concentrations in certain regions. To address this challenge, we have developed an efficient three-dimensional computational fluid dynamics (CFD) code called Aeolus that is based on first principles for predicting transport and dispersion of materials in complex terrain and urban areas. The model can be run in a very efficient Reynolds average Navier–Stokes (RANS) mode or a detailed large eddy simulation (LES) mode. The RANS version of Aeolus was previously validated against field data for tracer gas and radiological dispersal releases. As a part of this work, we have validated the Aeolus model in LES mode against two different sets of data: (1) turbulence quantities measured in complex terrain at Askervein Hill; and (2) wind and tracer data from the Joint Urban 2003 field campaign for urban topography. As a third set-up, we have applied Aeolus to simulate cloud rise dynamics for buoyant plumes from high-temperature explosions. For all three cases, Aeolus LES predictions compare well to observations and other models. These results indicate that Aeolus LES can be used to accurately simulate turbulent flow and transport for a wide range of applications and scales. Full article

(This article belongs to the Special Issue High Performance Computing Serving Atmospheric Transport & Dispersion Modelling)

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16 pages, 13942 KiB

Open AccessEditor’s ChoiceArticle

Defining Heatwaves with Respect to Human Biometeorology. The Case of Attica Region, Greece

by Lida Dimitriadou, Panagiotis Nastos and Christos Zerefos

Atmosphere 2021, 12(9), 1100; https://doi.org/10.3390/atmos12091100 - 25 Aug 2021

Cited by 7 | Viewed by 3164

Abstract

To date, due to climate change, heatwaves are more frequent, with greater intensity and duration resulting in deleterious impacts on human health. To be able to manage heatwaves and quantify the impacts on human health, it is crucial to define them and implement [...] Read more.

To date, due to climate change, heatwaves are more frequent, with greater intensity and duration resulting in deleterious impacts on human health. To be able to manage heatwaves and quantify the impacts on human health, it is crucial to define them and implement policy preventive measures. However, heatwaves are relative to the climate of a location: The same meteorological conditions can constitute a heatwave in one place but not in another. Due to different climatic conditions, social characteristics, and adaptation, heatwaves should be defined on a local scale, which poses difficulties when it comes to comparison of different definitions. The aim of the present study is to define heatwaves, implementing robust statistical analysis for three different indicators (temperature, physiological equivalent temperature (PET), and universal thermal climate index (UTCI)) for three causes of mortality (i.e., cardiological and respiratory mortality and cardiorespiratory mortality) using Attica (Greece) as a case study. Our results define a heatwave for Attica as a period of at least 3 days when the mean temperature is higher than the 97.5th percentile. Afterwards, we encapsulate the harvesting effect by implementing robust statistical analysis, using the Superposed Epoch analysis. Consequently, quantifying heatwaves is crucial so as to create early warning systems and prevent avoidable mortality. Full article

(This article belongs to the Section Biometeorology)

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21 pages, 10145 KiB

Open AccessEditor’s ChoiceArticle

Impact of Soil Moisture Data Assimilation on Analysis and Medium-Range Forecasts in an Operational Global Data Assimilation and Prediction System

by Sanghee Jun, Jeong-Hyun Park, Hyun-Joo Choi, Yong-Hee Lee, Yoon-Jin Lim, Kyung-On Boo and Hyun-Suk Kang

Atmosphere 2021, 12(9), 1089; https://doi.org/10.3390/atmos12091089 - 24 Aug 2021

Cited by 5 | Viewed by 2298

Abstract

Accurate initial soil moisture conditions are essential for numerical weather prediction models, because they play a major role in land–atmosphere interactions. This study constructed a soil moisture data assimilation system and evaluated its impacts on the Global Data Assimilation and Prediction System based [...] Read more.

Accurate initial soil moisture conditions are essential for numerical weather prediction models, because they play a major role in land–atmosphere interactions. This study constructed a soil moisture data assimilation system and evaluated its impacts on the Global Data Assimilation and Prediction System based on the Korea Integrated Model (GDAPS-KIM) to improve its weather forecast skill. Soil moisture data retrieved from the Advanced Scatterometer (ASCAT) onboard the Meteorological Operational Satellite was assimilated into GDAPS-KIM using the ensemble Kalman filter method, and its impacts were evaluated for the 2019 boreal summer period. Our results indicated that the soil moisture data assimilation improved the agreement of the observations with the initial conditions of GDAPS-KIM. This led to a statistically significant improvement in the accuracy of the initial fields. A comparison of a five-day forecast against an ERA5 reanalysis and in situ observations revealed a reduction in the dry and warm biases of GDAPS-KIM over the surface and in the lower- and mid-level atmospheres. The temperature bias correction through the initialization of the soil moisture estimates from the data assimilation system was shown in the five-day weather forecast (root mean squared errors reduction of the temperature at 850 hPa by approximately 5% in East Asia). Full article

(This article belongs to the Section Atmospheric Techniques, Instruments, and Modeling)

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26 pages, 5519 KiB

Open AccessEditor’s ChoiceArticle

Adaptive Crop Management under Climate Uncertainty: Changing the Game for Sustainable Water Use

by Soe W. Myint, Rimjhim Aggarwal, Baojuan Zheng, Elizabeth A. Wentz, Jim Holway, Chao Fan, Nancy J. Selover, Chuyuan Wang and Heather A. Fischer

Atmosphere 2021, 12(8), 1080; https://doi.org/10.3390/atmos12081080 - 23 Aug 2021

Cited by 5 | Viewed by 3680

Abstract

Water supplies are projected to become increasingly scarce, driving farmers, energy producers, and urban dwellers towards an urgent and emerging need to improve the effectiveness and the efficiency of water use. Given that agricultural water use is the largest water consumer throughout the [...] Read more.

Water supplies are projected to become increasingly scarce, driving farmers, energy producers, and urban dwellers towards an urgent and emerging need to improve the effectiveness and the efficiency of water use. Given that agricultural water use is the largest water consumer throughout the U.S. Southwest, this study sought to answer two specific research questions: (1) How does water consumption vary by crop type on a metropolitan spatial scale? (2) What is the impact of drought on agricultural water consumption? To answer the above research questions, 92 Landsat images were acquired to generate fine-resolution daily evapotranspiration (ET) maps at 30 m spatial resolution for both dry and wet years (a total of 1095 ET maps), and major crop types were identified for the Phoenix Active Management Area. The study area has a subtropical desert climate and relies almost completely on irrigation for farming. Results suggest that there are some factors that farmers and water managers can control. During dry years, crops of all types use more water. Practices that can offset this higher water use include double or multiple cropping practice, drought tolerant crop selection, and optimizing the total farmed area. Double and multiple cropping practices result in water savings because soil moisture is retained from one planting to another. Further water savings occur when drought tolerant crop types are selected, especially in dry years. Finally, disproportionately large area coverage of high water consuming crops can be balanced and/or reduced or replaced with more water efficient crops. This study provides strong evidence that water savings can be achieved through policies that create incentives for adopting smart cropping strategies, thus providing important guidelines for sustainable agriculture management and climate adaptation to improve future food security. Full article

(This article belongs to the Special Issue Remote Sensing and GIS Applications in Urban Climate Research)

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17 pages, 4831 KiB

Open AccessEditor’s ChoiceArticle

30 Years of Air Quality Trends in Japan

by Akiyoshi Ito, Shinji Wakamatsu, Tazuko Morikawa and Shinji Kobayashi

Atmosphere 2021, 12(8), 1072; https://doi.org/10.3390/atmos12081072 - 21 Aug 2021

Cited by 35 | Viewed by 10274

Abstract

The aim of this paper is to obtain information that will contribute to measures and research needed to further improve the air quality in Japan. The trends and characteristics of air pollutant concentrations, especially PM_2.5, ozone, and related substances, over the past [...] Read more.

The aim of this paper is to obtain information that will contribute to measures and research needed to further improve the air quality in Japan. The trends and characteristics of air pollutant concentrations, especially PM_2.5, ozone, and related substances, over the past 30 years, are analyzed, and the relationships between concentrations and emissions are discussed quantitatively. We found that PM_2.5 mass concentrations have decreased, with the largest reduction in elemental carbon (EC) as the PM_2.5 component. The concentrations of organic carbon (OC) have not changed significantly compared to other components, suggesting that especially VOC emissions as precursors need to be reduced. In addition, the analysis of the differences in PM_2.5 concentrations between the ambient and the roadside showed that further research on non-exhaust particles is needed. For NOx and SO₂, there is a linear relationship between domestic anthropogenic emissions and atmospheric concentrations, indicating that emission control measures are directly effective in the reduction in concentrations. Also, recent air pollution episodes and the effect of reduced economic activity, as a consequence of COVID-19, on air pollution concentrations are summarized. Full article

(This article belongs to the Special Issue Air Pollution in Japan)

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12 pages, 563 KiB

Open AccessEditor’s ChoiceReview

Effects of PM_2.5 on Chronic Airway Diseases: A Review of Research Progress

by Xin Li and Xiaoju Liu

Atmosphere 2021, 12(8), 1068; https://doi.org/10.3390/atmos12081068 - 20 Aug 2021

Cited by 14 | Viewed by 4544

Abstract

The adverse effects of polluted air on human health have been increasingly appreciated worldwide. It is estimated that outdoor air pollution is associated with the death of 4.2 million people globally each year. Accumulating epidemiological studies indicate that exposure to ambient fine particulate [...] Read more.

The adverse effects of polluted air on human health have been increasingly appreciated worldwide. It is estimated that outdoor air pollution is associated with the death of 4.2 million people globally each year. Accumulating epidemiological studies indicate that exposure to ambient fine particulate matter (PM_2.5), one of the important air pollutants, significantly contributes to respiratory mortality and morbidity. PM_2.5 causes lung damage mainly by inducing inflammatory response and oxidative stress. In this paper, we reviewed the research results of our group on the effects of PM_2.5 on chronic obstructive pulmonary disease, asthma, and lung cancer. And recent research progress on epidemiological studies and potential mechanisms were also discussed. Reducing air pollution, although remaining a major challenge, is the best and most effective way to prevent the onset and progression of respiratory diseases. Full article

(This article belongs to the Special Issue Outdoor Air Pollution and Human Health)

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28 pages, 7948 KiB

Open AccessEditor’s ChoiceArticle

Fine-Resolution WRF Simulation of Stably Stratified Flows in Shallow Pre-Alpine Valleys: A Case Study of the KASCADE-2017 Campaign

by Michiel de Bode, Thierry Hedde, Pierre Roubin and Pierre Durand

Atmosphere 2021, 12(8), 1063; https://doi.org/10.3390/atmos12081063 - 19 Aug 2021

Cited by 11 | Viewed by 2485

Abstract

In an overall approach aiming at the development and qualification of various tools designed to diagnose and/or forecast the flows at the local scale in complex terrain, we qualified a numerical model based on the WRF platform and operated in a two-way nested [...] Read more.

In an overall approach aiming at the development and qualification of various tools designed to diagnose and/or forecast the flows at the local scale in complex terrain, we qualified a numerical model based on the WRF platform and operated in a two-way nested domain mode, down to a horizontal resolution of 111 m for the smallest domain. The area in question is the Cadarache valley (CV), in southeast France, which is surrounded by hills and valleys of various sizes. The CV dimensions (1 km wide and 100 m deep) favor the development of local flows greatly influenced by the diurnal cycle and are prone to thermal stratification, especially during stable conditions. This cycle was well documented due to permanent observations and dedicated field campaigns. These observations were used to evaluate the performance of the model on a specific day among the intensive observation periods carried out during the KASCADE-2017 campaign. The model reproduced the wind flow and its diurnal cycle well, notably at the local CV scale, which constitutes considerable progress with respect to the performances of previous WRF simulations conducted in this area with kilometric resolution, be it operational weather forecasts or dedicated studies conducted on specific days. The diurnal temperature range is underestimated however, together with the stratification intensity of the cold pool observed at night. Consequently, the slope drainage flows along the CV sidewalls are higher in the simulation than in the observations, and the resulting scalar fields (such as specific humidity) are less heterogeneous in the model than in the observations. Full article

(This article belongs to the Special Issue The Stable Boundary Layer: Observations and Modeling)

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10 pages, 36951 KiB

Open AccessEditor’s ChoiceArticle

Extreme Translation Events of Atlantic Tropical Cyclones

by Wei Zhang

Atmosphere 2021, 12(8), 1032; https://doi.org/10.3390/atmos12081032 - 12 Aug 2021

Cited by 2 | Viewed by 1814

Abstract

Changes in the translational speed of tropical cyclones (e.g., sluggish tropical cyclones) are associated with extreme precipitation and flash flooding. However, it is still unclear regarding the spatial and temporal variability of extreme tropical cyclone translation events in the North Atlantic and underlying [...] Read more.

Changes in the translational speed of tropical cyclones (e.g., sluggish tropical cyclones) are associated with extreme precipitation and flash flooding. However, it is still unclear regarding the spatial and temporal variability of extreme tropical cyclone translation events in the North Atlantic and underlying large-scale drivers. This work finds that the frequencies of extreme fast- and slow-translation events of Atlantic tropical cyclones exhibited a significant rising trend during 1980–2019. The extreme fast-translation events of Atlantic tropical cyclones are primarily located in the northern part of the North Atlantic, while the extreme slow-translation events are located more equatorward. There is a significant rising trend in the frequency of extreme slow-translation events over ocean with no trend over land. However, there is a significant rising trend in the frequency of extreme fast-translation events over ocean and over land. The extreme slow-translation events are associated with a strong high-pressure system in the continental United States (U.S.). By contrast, the extreme fast-translation events are related to a low-pressure system across most of the continental U.S. that leads to westerly steering flow that enhances tropical cyclone movement. This study suggests that it might be useful to separate tropical cyclone events into fast-moving and slow-moving groups when examining the translational speed of North Atlantic tropical cyclones, instead of examining regional or global mean translational speed. Full article

(This article belongs to the Special Issue Extreme Tropical Cyclones)

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17 pages, 5986 KiB

Open AccessEditor’s ChoiceArticle

Characteristics of Enhanced Heatwaves over Tanzania and Scenario Projection in the 21st Century

by Amatus Gyilbag, Martial Amou, Roberto Xavier Supe Tulcan, Lei Zhang, Tsedale Demelash and Yinlong Xu

Atmosphere 2021, 12(8), 1026; https://doi.org/10.3390/atmos12081026 - 11 Aug 2021

Cited by 5 | Viewed by 2875

Abstract

Extreme hot temperature is dangerous to the bioeconomy, and would worsen with time. Ambient heatwaves accompanied by unusual droughts are major threats to poverty eradication in Tanzania. Due to sparsity of observation data and proper heatwave detection metrics, there has been a paucity [...] Read more.

Extreme hot temperature is dangerous to the bioeconomy, and would worsen with time. Ambient heatwaves accompanied by unusual droughts are major threats to poverty eradication in Tanzania. Due to sparsity of observation data and proper heatwave detection metrics, there has been a paucity of knowledge about heatwave events in Tanzania. In this study, the Heatwave Magnitude Index daily (HWMId) was adopted to quantitatively analyze heatwave characteristics throughout Tanzania at mid-21st century (2041–2070) and end of 21st century (2071–2100), relative to the reference period (1983–2012) using the CHIRTS-daily quasi-global high-resolution temperature dataset and climate simulations from a multi-modal ensemble of median scenarios (RCP4.5, from CORDEX-Africa). The results showed that moderate to super-extreme heatwaves occurred in Tanzania between 1983 and 2012, particularly in 1999, when ultra-extreme heatwaves (HWMId > 32) occurred in the Lake Victoria basin. It is projected that by mid-21st century, the upper category of HWMId would be hotter and longer, and would occur routinely in Tanzania. The spatial extent of all of the HWMId categories is projected to range from 34% to 73% by the end of the 21st century with a duration of 8 to 35 days, compared to 1 to 5 days during the reference period. These findings will contribute to increasing public awareness of the need for adaptation. Full article

(This article belongs to the Section Biometeorology)

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25 pages, 10061 KiB

Open AccessEditor’s ChoiceArticle

On the Relationship of Cold Pool and Bulk Shear Magnitudes on Upscale Convective Growth in the Great Plains of the United States

by Zachary A. Hiris and William A. Gallus, Jr.

Atmosphere 2021, 12(8), 1019; https://doi.org/10.3390/atmos12081019 - 9 Aug 2021

Cited by 2 | Viewed by 2893

Abstract

Upscale convective growth remains a poorly understood aspect of convective evolution, and numerical weather prediction models struggle to accurately depict convective morphology. To better understand some physical mechanisms encouraging upscale growth, 30 warm-season convective events from 2016 over the United States Great Plains [...] Read more.

Upscale convective growth remains a poorly understood aspect of convective evolution, and numerical weather prediction models struggle to accurately depict convective morphology. To better understand some physical mechanisms encouraging upscale growth, 30 warm-season convective events from 2016 over the United States Great Plains were simulated using the Weather Research and Forecasting (WRF) model to identify differences in upscale growth and non-upscale growth environments. Also, Bryan Cloud Model (CM1) sensitivity tests were completed using different thermodynamic environments and wind profiles to examine the impact on upscale growth. The WRF simulations indicated that cold pools are significantly stronger in cases that produce upscale convective growth within the first few hours following convective initiation compared to those without upscale growth. Conversely, vertical wind shear magnitude has no statistically significant relationship with either MCS or non-MCS events. This is further supported by the CM1 simulations, in which tests using the WRF MCS sounding developed a large convective system in all tests performed, including one which used the non-MCS kinematic profile. Likewise, the CM1 simulations of the non-upscale growth event did not produce an MCS, even when using the MCS kinematic profile. Overall, these results suggest that the near-storm and pre-convective thermodynamic environment may play a larger role than kinematics in determining upscale growth potential in the Great Plains. Full article

(This article belongs to the Section Meteorology)

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17 pages, 435 KiB

Open AccessEditor’s ChoiceArticle

The Impact of Smog Pollution on Audit Quality: Evidence from China

by Bin Li, Ying Zhou, Tingyu Zhang and Yang Liu

Atmosphere 2021, 12(8), 1015; https://doi.org/10.3390/atmos12081015 - 7 Aug 2021

Cited by 5 | Viewed by 2585

Abstract

Audit quality usually refers to the quality that the auditing services accounting firm auditors provide to an enterprise in the form of an audit report. This study empirically analyzes the impact mechanism of smog pollution on audit quality, based on the data of [...] Read more.

Audit quality usually refers to the quality that the auditing services accounting firm auditors provide to an enterprise in the form of an audit report. This study empirically analyzes the impact mechanism of smog pollution on audit quality, based on the data of A-share listed companies in the Shanghai and Shenzhen Stock Exchanges during the period 2013 to 2017 and the air quality monitoring data released by the China National Environmental Monitoring Centre covering the period 2013 to 2018. First, the empirical results show that smog pollution can lead to a decline in audit quality. Second, audit time plays a partial mediating role in the relationship between smog pollution and audit quality. Further analysis indicates that the negative impact of smog pollution on audit quality and the intermediary role played by audit time are only significant in the sample of “top 10” accounting firms. Third, the enterprise′s internal control level positively moderates the mediating effect of audit time on smog pollution and audit quality. Full article

(This article belongs to the Special Issue Aerosol Pollution in Asia)

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30 pages, 5889 KiB

Open AccessEditor’s ChoiceArticle

Air Quality in the Italian Northwestern Alps during Year 2020: Assessment of the COVID-19 «Lockdown Effect» from Multi-Technique Observations and Models

by Henri Diémoz, Tiziana Magri, Giordano Pession, Claudia Tarricone, Ivan Karl Friedrich Tombolato, Gabriele Fasano and Manuela Zublena

Atmosphere 2021, 12(8), 1006; https://doi.org/10.3390/atmos12081006 - 5 Aug 2021

Cited by 13 | Viewed by 3953

Abstract

The effect of COVID-19 confinement regulations on air quality in the northwestern Alps is assessed here based on measurements at five valley sites in different environmental contexts. Surface concentrations of nitrogen oxides (NO and NO

_{2}

), ozone (O

_{3}

), particulate matter [...] Read more.

The effect of COVID-19 confinement regulations on air quality in the northwestern Alps is assessed here based on measurements at five valley sites in different environmental contexts. Surface concentrations of nitrogen oxides (NO and NO

_{2}

), ozone (O

_{3}

), particulate matter (PM

_{2.5}

and PM

_{10}

), together with a thorough microphysical (size), chemical, and optical (light absorption) aerosol characterisation, complemented by observations along the vertical column are considered. Even in the relatively pristine environment of the Alps, the «lockdown effect» is well discernible, both in the early confinement phase and in late 2020. The variations observed during the first confinement period in the city of Aosta (−61% NO, −43% NO

_{2}

, +5% O

_{3}

, +9% PM

_{2.5}

, −12% PM

_{10}

, relative to average 2015–2019 conditions) are attributed to the competing effects of air pollution lockdown-induced changes (−74%, −52%, +18%, −13%, −27%, relative to the counterfactual scenario for 2020 provided by a predictive statistical model trained on past measurements) and meteorology (+52%, +18%, −11%, +25%, +20%, relative to average conditions). These changes agree well with the ones obtained from a chemical transport model with modified emissions according to the restrictions. With regard to column-integrated quantities and vertical profiles, the NO

_{2}

column density decreases by >20% due to the lockdown, whereas tropospheric aerosols are mainly influenced by large-scale dynamics (transport of secondary particles from the Po basin and mineral dust from the Sahara desert and the Caspian Sea), except a shallow layer about 500 m thick close to the surface, possibly sensitive to curtailed emissions (especially exhaust and non-exhaust particles from road traffic and fugitive emissions from the industry). Full article

(This article belongs to the Special Issue Air Pollution Changes and Impacts during Abrupt Shifts in Anthropogenic Activities)

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15 pages, 4136 KiB

Open AccessEditor’s ChoiceArticle

Environmental Factors Controlling the Precipitation in California

by Feng Hu, Leying Zhang, Qiao Liu and Dorina Chyi

Atmosphere 2021, 12(8), 997; https://doi.org/10.3390/atmos12080997 - 2 Aug 2021

Cited by 6 | Viewed by 2249

Abstract

Using observational data covering 1948–2020, the environmental factors controlling the winter precipitation in California were investigated. Empirical orthogonal function (EOF) analysis was applied to identify the dominant climate regimes contributing to the precipitation. The first EOF mode described a consistent change, with 70.1% [...] Read more.

Using observational data covering 1948–2020, the environmental factors controlling the winter precipitation in California were investigated. Empirical orthogonal function (EOF) analysis was applied to identify the dominant climate regimes contributing to the precipitation. The first EOF mode described a consistent change, with 70.1% variance contribution, and the second mode exhibited a south–east dipole change, with 11.7% contribution. For EOF1, the relationship was positive between PC1(principal component) and SST (sea surface temperature) in the central Pacific Ocean, while it was negative with SST in the southeast Indian Ocean. The Pacific–North America mode, induced by the positive SST and precipitation in the central Pacific Ocean, leads to California being occupied by southwesterlies, which would transport warm and wet flow from the ocean, beneficial for precipitation. As for the negative relationship, California is controlled by biotrophically high pressure, representing part of the Rossby wave train induced by the positive SST in the Indian ocean, which is unfavorable for the precipitation. For EOF2, California is controlled by positive vorticity at the upper level, whereas at the lower level, there is positive vorticity to the south and negative vorticity to the north, the combination of which leads to the dipole mode change in the precipitation. Full article

(This article belongs to the Special Issue Tropical Ocean-Atmosphere Interaction and Climate Change)

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19 pages, 9193 KiB

Open AccessEditor’s ChoiceArticle

Experimental Comparative Study between Conventional and Green Parking Lots: Analysis of Subsurface Thermal Behavior under Warm and Dry Summer Conditions

by Ryad Bouzouidja, François Leconte, Márton Kiss, Margaux Pierret, Christelle Pruvot, Sébastien Détriché, Brice Louvel, Julie Bertout, Zakaria Aketouane, Tingting Vogt Wu, Rémy Goiffon, Baptiste Colin, Anélie Pétrissans, Philippe Lagière and Mathieu Pétrissans

Atmosphere 2021, 12(8), 994; https://doi.org/10.3390/atmos12080994 - 31 Jul 2021

Cited by 8 | Viewed by 3864

Abstract

Green infrastructure has a role to play in climate change adaptation strategies in cities. Alternative urban spaces should be designed considering new requirements in terms of urban microclimate and thermal comfort. Pervious pavements such as green parking lots can contribute to this goal [...] Read more.

Green infrastructure has a role to play in climate change adaptation strategies in cities. Alternative urban spaces should be designed considering new requirements in terms of urban microclimate and thermal comfort. Pervious pavements such as green parking lots can contribute to this goal through solar evaporative cooling. However, the cooling benefits of such systems remain under debate during dry and warm periods. The aim of this study was to compare experimentally the thermal behavior of different parking lot types (PLTs) with vegetated urban soil. Four parking lots were instrumented, with temperature probes buried at different depths. Underground temperatures were measured during summer 2019, and the hottest days of the period were analyzed. Results show that the less mineral used in the surface coating, the less it warms up. The temperature difference at the upper layer can reach 10 °C between mineral and non-mineral PLTs. PLTs can be grouped into three types: (i) high surface temperature during daytime and nighttime, important heat transfer toward the sublayers, and low time shift (asphalt system); (ii) high (resp. low) surface temperature during daytime (resp. nighttime), weak heat transfer toward the sublayers, and important time shift (paved stone system); and (iii) low surface temperature during daytime and nighttime, weak heat transfer toward the sublayers, and important time shift (vegetation and substrate system, wood chips system, vegetated urban soil). The results of this study underline that pervious pavements demonstrate thermal benefits under warm and dry summer conditions compared to conventional parking lot solutions. The results also indicate that the hygrothermal properties of urban materials are crucial for urban heat island mitigation. Full article

(This article belongs to the Special Issue Outdoor Thermal Comfort in Cities: Assessing and Developing Green, Blue and Grey Solutions for Healthy and Sustainable Urban Future)

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25 pages, 5467 KiB

Open AccessEditor’s ChoiceArticle

A CFD Approach for Risk Assessment Based on Airborne Pathogen Transmission

by Hamid Motamedi Zoka, Mohammad Moshfeghi, Hadi Bordbar, Parham A. Mirzaei and Yahya Sheikhnejad

Atmosphere 2021, 12(8), 986; https://doi.org/10.3390/atmos12080986 - 30 Jul 2021

Cited by 11 | Viewed by 3655

Abstract

The outbreak of COVID-19 necessitates developing reliable tools to derive safety measures, including safe social distance and minimum exposure time under different circumstances. Transient Eulerian–Lagrangian computational fluid dynamics (CFD) models have emerged as a viably fast and economical option. Nonetheless, these CFD models [...] Read more.

The outbreak of COVID-19 necessitates developing reliable tools to derive safety measures, including safe social distance and minimum exposure time under different circumstances. Transient Eulerian–Lagrangian computational fluid dynamics (CFD) models have emerged as a viably fast and economical option. Nonetheless, these CFD models resolve the instantaneous distribution of droplets inside a computational domain, making them incapable of directly being used to assess the risk of infection as it depends on the total accumulated dosage of infecting viruses received by a new host within an exposure time. This study proposes a novel risk assessment model (RAM) to predict the temporal and spatial accumulative concentration of infectious exhaled droplets based on the bio-source’s exhalation profile and droplet distribution using the CFD results of respiratory events in various environmental conditions. Unlike the traditional approach in the bulk movement assessment of droplets’ outreach in a domain, every single droplet is traced inside the domain at each time step, and the total number of droplets passing through any arbitrary position of the domain is determined using a computational code. The performance of RAM is investigated for a series of case studies against various respiratory events where the horizontal and the lateral spread of risky zones are shown to temporarily vary rather than being fixed in space. The sensitivity of risky zones to ambient temperature and relative humidity was also addressed for sample cough and sneeze cases. This implies that the RAM provides crucial information required for defining safety measures such as safety distances or minimum exposure times in different environments. Full article

(This article belongs to the Special Issue Transport Phenomena in the Atmospheric Boundary Layer)

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14 pages, 4701 KiB

Open AccessEditor’s ChoiceArticle

Spatial and Temporal Characteristics of Rainfall Anomalies in 1961–2010 in the Yangtze River Basin, China

by Shuying Bai, Jixi Gao, Yu Xue and Romany Mansour

Atmosphere 2021, 12(8), 960; https://doi.org/10.3390/atmos12080960 - 27 Jul 2021

Cited by 8 | Viewed by 1931

Abstract

Understanding rainfall anomalies and their relationship with floods in the Yangtze River Basin (YRB) is essential for evaluating flood disasters, which have a great impact on the development of agriculture and the economy. On the basis of daily rainfall data from 1961 to [...] Read more.

Understanding rainfall anomalies and their relationship with floods in the Yangtze River Basin (YRB) is essential for evaluating flood disasters, which have a great impact on the development of agriculture and the economy. On the basis of daily rainfall data from 1961 to 2010 from 178 meteorological stations, the temporal and spatial characteristics of rainfall anomalies in the YRB were studied on an annual scale, seasonal scale, and monthly scale. The annual rainfall of the YRB showed a generally increasing trend from 1961 to 2010 (14.22 mm/10 a). By means of the Bernaola–Galvan abrupt change test and Redfit spectrum analysis, it was found that the annual average rainfall increased abruptly after 1979 and had a cycle of 2–3 years. On the seasonal scale, the rainfall in spring and autumn showed a gradually decreasing trend, especially in September, while it showed a significant increasing trend in summer and winter in the YRB. As for the monthly scale, the rainfall in the rainy season from June to July presented a clear increasing trend during the study period, which greatly enhanced the probability of floods in the YRB. Additionally, through the analysis of the spatial distribution characteristics of rainfall in the entire YRB from 1961 to 2010, it was observed that the annual rainfall amount in the YRB presented an “increase–decrease–increase” tendency from east to west, accompanied by a rain belt that continuously moved from west to east. Moreover, the rainfall characteristics in flood years were summarized, and the results revealed that the years with rainfall anomalies were more likely to have flood disasters. However, anomalies alone would not result in big floods; the spatially and temporally inhomogeneous rainfall distribution might be the primary reason for flood disasters in the entire YRB. Full article

(This article belongs to the Special Issue Recent Advances and Future Prospects of Machine Learning in Predictive Modeling of Atmospheric Sciences)

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20 pages, 7306 KiB

Open AccessEditor’s ChoiceArticle

Assessment of Low-Cost Particulate Matter Sensor Systems against Optical and Gravimetric Methods in a Field Co-Location in Norway

by Matthias Vogt, Philipp Schneider, Nuria Castell and Paul Hamer

Atmosphere 2021, 12(8), 961; https://doi.org/10.3390/atmos12080961 - 27 Jul 2021

Cited by 29 | Viewed by 4498

Abstract

The increased availability of commercially-available low-cost air quality sensors combined with increased interest in their use by citizen scientists, community groups, and professionals is resulting in rapid adoption, despite data quality concerns. We have characterized three out-the-box PM sensor systems under different environmental [...] Read more.

The increased availability of commercially-available low-cost air quality sensors combined with increased interest in their use by citizen scientists, community groups, and professionals is resulting in rapid adoption, despite data quality concerns. We have characterized three out-the-box PM sensor systems under different environmental conditions, using field colocation against reference equipment. The sensor systems integrate Plantower 5003, Sensirion SPS30 and Alphasense OCP-N3 PM sensors. The first two use photometry as a measuring technique, while the third one is an optical particle counter. For the performance evaluation, we co-located 3 units of each manufacturer and compared the results against optical (FIDAS) and gravimetric (KFG) methods for a period of 7 weeks (28 August to 19 October 2020). During the period from 2nd and 5th October, unusually high PM concentrations were observed due to a long-range transport episode. The results show that the highest correlations between the sensor systems and the optical reference are observed for PM₁, with coefficients of determination above 0.9, followed by PM_2.5. All the sensor units struggle to correctly measure PM₁₀, and the coefficients of determination vary between 0.45 and 0.64. This behavior is also corroborated when using the gravimetric method, where correlations are significantly higher for PM_2.5 than for PM₁₀, especially for the sensor systems based on photometry. During the long range transport event the performance of the photometric sensors was heavily affected, and PM₁₀ was largely underestimated. The sensor systems evaluated in this study had good agreement with the reference instrumentation for PM₁ and PM_2.5; however, they struggled to correctly measure PM₁₀. The sensors also showed a decrease in accuracy when the ambient size distribution was different from the one for which the manufacturer had calibrated the sensor, and during weather conditions with high relative humidity. When interpreting and communicating air quality data measured using low-cost sensor systems, it is important to consider such limitations in order not to risk misinterpretation of the resulting data. Full article

(This article belongs to the Special Issue The Future of Air Quality Monitoring)

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24 pages, 7241 KiB

Open AccessEditor’s ChoiceArticle

Turbulent Momentum Flux Behavior above a Fire Front in an Open-Canopied Forest

by Warren E. Heilman, Kenneth L. Clark, Xindi Bian, Joseph J. Charney, Shiyuan Zhong, Nicholas S. Skowronski, Michael R. Gallagher and Matthew Patterson

Atmosphere 2021, 12(8), 956; https://doi.org/10.3390/atmos12080956 - 24 Jul 2021

Cited by 5 | Viewed by 1806

Abstract

Atmospheric turbulent circulations in the vicinity of wildland fire fronts play an important role in the transfer of momentum into and out of combustion zones, which in turn can potentially affect the behavior and spread of wildland fires. The vertical turbulent transfer of [...] Read more.

Atmospheric turbulent circulations in the vicinity of wildland fire fronts play an important role in the transfer of momentum into and out of combustion zones, which in turn can potentially affect the behavior and spread of wildland fires. The vertical turbulent transfer of momentum is accomplished via individual sweep, ejection, outward interaction, and inward interaction events, collectively known as sweep-ejection dynamics. This study examined the sweep-ejection dynamics that occurred before, during, and after the passage of a surface fire front during a prescribed fire experiment conducted in an open-canopied forest in the New Jersey Pine Barrens. High-frequency (10 Hz), tower-based, sonic anemometer measurements of horizontal and vertical wind velocity components in the vicinity of the fire front were used to assess the relative frequencies of occurrence of the different types of momentum-flux events, their contributions to the overall momentum fluxes, and their periodicity patterns. The observational results suggest that the presence of surface fire fronts in open-canopied forests can substantially change the sweep-ejection dynamics that typically occur when fires are not present. In particular, sweep events resulting in the downward transport of high horizontal momentum air from above were found to be more prominent during fire-front-passage periods. Full article

(This article belongs to the Section Biometeorology)

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22 pages, 4050 KiB

Open AccessEditor’s ChoiceArticle

Expected Health Effects of Reduced Air Pollution from COVID-19 Social Distancing

by Steve Cicala, Stephen P. Holland, Erin T. Mansur, Nicholas Z. Muller and Andrew J. Yates

Atmosphere 2021, 12(8), 951; https://doi.org/10.3390/atmos12080951 - 23 Jul 2021

Cited by 20 | Viewed by 4834

Abstract

The COVID-19 pandemic resulted in stay-at-home policies and other social distancing behaviors in the United States in spring of 2020. This paper examines the impact that these actions had on emissions and expected health effects through reduced personal vehicle travel and electricity consumption. [...] Read more.

The COVID-19 pandemic resulted in stay-at-home policies and other social distancing behaviors in the United States in spring of 2020. This paper examines the impact that these actions had on emissions and expected health effects through reduced personal vehicle travel and electricity consumption. Using daily cell phone mobility data for each U.S. county, we find that vehicle travel dropped about 40% by mid-April across the nation. States that imposed stay-at-home policies before March 28 decreased travel slightly more than other states, but travel in all states decreased significantly. Using data on hourly electricity consumption by electricity region (e.g., balancing authority), we find that electricity consumption fell about 6% on average by mid-April with substantial heterogeneity. Given these decreases in travel and electricity use, we estimate the county-level expected improvements in air quality, and, therefore, expected declines in mortality. Overall, we estimate that, for a month of social distancing, the expected premature deaths due to air pollution from personal vehicle travel and electricity consumption declined by approximately 360 deaths, or about 25% of the baseline 1500 deaths. In addition, we estimate that CO₂ emissions from these sources fell by 46 million metric tons (a reduction of approximately 19%) over the same time frame. Full article

(This article belongs to the Special Issue Human Health, Climate Change, and Ambient Air Pollution)

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17 pages, 5355 KiB

Open AccessEditor’s ChoiceArticle

Spatial Distribution of Black Carbon Concentrations in the Atmosphere of the North Atlantic and the European Sector of the Arctic Ocean

by Sergey M. Sakerin, Dmitry M. Kabanov, Vladimir M. Kopeikin, Ivan A. Kruglinsky, Alexander N. Novigatsky, Viktor V. Pol’kin, Vladimir P. Shevchenko and Yuri S. Turchinovich

Atmosphere 2021, 12(8), 949; https://doi.org/10.3390/atmos12080949 - 23 Jul 2021

Cited by 11 | Viewed by 2435

Abstract

We discuss the measurements of black carbon concentrations in the composition of atmospheric aerosol over the seas of the North Atlantic and European sector of the Arctic Ocean (21 expeditions in 2007–2020). The black carbon concentrations were measured by an aethalometer and filter [...] Read more.

We discuss the measurements of black carbon concentrations in the composition of atmospheric aerosol over the seas of the North Atlantic and European sector of the Arctic Ocean (21 expeditions in 2007–2020). The black carbon concentrations were measured by an aethalometer and filter method. The comparison of the two variants of the measurements of the black carbon concentrations showed that the data acceptably agreed and can be used jointly. It is noted that the spatial distribution of black carbon over the ocean is formed under the influence of outflows of air masses from the direction of continents, where the main sources of emission of absorbing aerosol are concentrated. We analyzed the statistical characteristics of black carbon concentrations in five marine regions, differing by the outflows of continental aerosol. The largest black carbon content is a salient feature of the atmosphere of the North and Baltic Seas, surrounded by land: average values of concentrations are 210 ng/m³, and modal values are 75 ng/m³. In other regions (except in the south of the Barents Sea), the average black carbon concentrations are 37–44 ng/m³ (modal concentrations are 18–26 ng/m³). We discuss the specific features of the spatial (latitude-longitude) distributions of black carbon concentrations, relying on ship-based measurements and model calculations (MERRA-2 reanalysis data). A common regularity of the experimental and model spatial distributions of black carbon is that the concentrations decrease in the northern direction and with the growing distance from the continent: from several hundred ng/m³ in the southern part of the North Sea to values below 50 ng/m³ in polar regions of the ocean. Full article

(This article belongs to the Special Issue Air Pollution in the Polar Regions: Levels, Sources and Trends)

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14 pages, 2734 KiB

Open AccessEditor’s ChoiceArticle

Atmospheric Wind Field Modelling with OpenFOAM for Near-Ground Gas Dispersion

by Sebastian Schalau, Abdelkarim Habib and Simon Michel

Atmosphere 2021, 12(8), 933; https://doi.org/10.3390/atmos12080933 - 21 Jul 2021

Cited by 2 | Viewed by 3316

Abstract

CFD simulations of near-ground gas dispersion depend significantly on the accuracy of the wind field. When simulating wind fields with conventional RANS turbulence models, the velocity and turbulence profiles specified as inlet boundary conditions change rapidly in the approach flow region. As a [...] Read more.

CFD simulations of near-ground gas dispersion depend significantly on the accuracy of the wind field. When simulating wind fields with conventional RANS turbulence models, the velocity and turbulence profiles specified as inlet boundary conditions change rapidly in the approach flow region. As a result, when hazardous materials are released, the extent of hazardous areas is calculated based on an approach flow that differs significantly from the boundary conditions defined. To solve this problem, a turbulence model with consistent boundary conditions was developed to ensure a horizontally homogeneous approach flow. Instead of the logarithmic vertical velocity profile, a power law is used to overcome the problem that with the logarithmic profile, negative velocities would be calculated for heights within the roughness length. With this, the problem that the distance of the wall-adjacent cell midpoint has to be higher than the roughness length is solved, so that a high grid resolution can be ensured even in the near-ground region which is required to simulate gas dispersion. The evaluation of the developed CFD model using the German guideline VDI 3783/9 and wind tunnel experiments with realistic obstacle configurations showed a good agreement between the calculated and the measured values and the ability to achieve a horizontally homogenous approach flow. Full article

(This article belongs to the Special Issue High Performance Computing Serving Atmospheric Transport & Dispersion Modelling)

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20 pages, 3708 KiB

Open AccessEditor’s ChoiceArticle

An Empirical Atmospheric Density Calibration Model Based on Long Short-Term Memory Neural Network

by Yan Zhang, Jinjiang Yu, Junyu Chen and Jizhang Sang

Atmosphere 2021, 12(7), 925; https://doi.org/10.3390/atmos12070925 - 17 Jul 2021

Cited by 7 | Viewed by 2662

Abstract

The accuracy of the atmospheric mass density is one of the most important factors affecting the orbital precision of spacecraft at low Earth orbits (LEO). Although there are a number of empirical density models available to use in the orbit determination and prediction [...] Read more.

The accuracy of the atmospheric mass density is one of the most important factors affecting the orbital precision of spacecraft at low Earth orbits (LEO). Although there are a number of empirical density models available to use in the orbit determination and prediction of LEO spacecraft, all of them suffer from errors of various degrees. A practical way to reduce the error of a particular model is to calibrate the model using precise density data or tracking data. In this paper, a long short-term memory (LSTM) neural network is proposed to calibrate the NRLMSISE-00 density model, in which the densities derived from spaceborne accelerometer data are the main input. The resulted LSTM-NRL model, calibrated using the accelerometer data from Challenging Minisatellite Payload (CHAMP) satellite, is extensively experimented to evaluate the calibration performance. With data in one month to train the LSTM-NRL model, the model is shown to effectively reduce the root mean square error of the model densities outside the training window by more than 40% in various time spans and space weather environment. The LSTM-NRL model is also shown to have remarkable transferring performance when it is applied along the GRACE satellite orbits. Full article

(This article belongs to the Special Issue Recent Advances and Future Prospects of Machine Learning in Predictive Modeling of Atmospheric Sciences)

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31 pages, 28741 KiB

Open AccessEditor’s ChoiceArticle

Sensitivity of Simulations of Extreme Mediterranean Storms to the Specification of Sea Surface Temperature: Comparison of Cases of a Tropical-Like Cyclone and Explosive Cyclogenesis

by Omer Hagay and Steve Brenner

Atmosphere 2021, 12(7), 921; https://doi.org/10.3390/atmos12070921 - 17 Jul 2021

Cited by 2 | Viewed by 3079

Abstract

Local air-sea interaction over the Mediterranean may amplify the effects of climate change. This study investigates the sensitivity of simulations of two different high impact weather events to changes in the specification of sea surface temperature (SST) using a regional atmospheric model. First [...] Read more.

Local air-sea interaction over the Mediterranean may amplify the effects of climate change. This study investigates the sensitivity of simulations of two different high impact weather events to changes in the specification of sea surface temperature (SST) using a regional atmospheric model. First we assess the impact of specifying SST from two reanalysis data sets with differing spatial resolution. The simulated tropical-like cyclone (TLC) is slightly stronger in the case of the lower resolution SST which is warmer over the formation region, most notably in the maximum rainfall which is ~7% higher. The differences in the two explosive cyclone simulations are negligible, most likely due to intensification occurring mainly over land. We then test the sensitivity of the storms to a range of SST anomalies. The TLC showed a clear trend of increasing storm intensity as SST rises. These results suggest that SST plays a direct role in determining the intensity of the storm. For the explosive cyclone there is no clear trend in dynamical intensity except for the highest warming anomalies. However, the rainfall increases with the magnitude of the SST anomaly. Our results suggest that extreme weather events over the Mediterranean will become more extreme if SST increases as the climate warms, assuming that upper air conditions do not change. Full article

(This article belongs to the Section Meteorology)

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24 pages, 18706 KiB

Open AccessEditor’s ChoiceArticle

A 7-Year Climatology of Warm-Sector Heavy Rainfall over South China during the Pre-Summer Months

by Tao Chen and Da-Lin Zhang

Atmosphere 2021, 12(7), 914; https://doi.org/10.3390/atmos12070914 - 15 Jul 2021

Cited by 1 | Viewed by 2818

Abstract

In view of the limited predictability of heavy rainfall (HR) events and the limited understanding of the physical mechanisms governing the initiation and organization of the associated mesoscale convective systems (MCSs), a composite analysis of 58 HR events over the warm sector (i.e., [...] Read more.

In view of the limited predictability of heavy rainfall (HR) events and the limited understanding of the physical mechanisms governing the initiation and organization of the associated mesoscale convective systems (MCSs), a composite analysis of 58 HR events over the warm sector (i.e., far ahead of the surface cold front), referred to as WSHR events, over South China during the months of April to June 2008~2014 is performed in terms of precipitation, large-scale circulations, pre-storm environmental conditions, and MCS types. Results show that the large-scale circulations of the WSHR events can be categorized into pre-frontal, southwesterly warm and moist ascending airflow, and low-level vortex types, with higher frequency occurrences of the former two types. Their pre-storm environments are characterized by a deep moist layer with >50 mm column-integrated precipitable water, high convective available potential energy with the equivalent potential temperature of ≥340 K at 850 hPa, weak vertical wind shear below 400 hPa, and a low-level jet near 925 hPa with weak warm advection, based on atmospheric parameter composite. Three classes of the corresponding MCSs, exhibiting peak convective activity in the afternoon and the early morning hours, can be identified as linear-shaped, a leading convective line adjoined with trailing stratiform rainfall, and comma-shaped, respectively. It is found that many linear-shaped MCSs in coastal regions are triggered by local topography, enhanced by sea breezes, whereas the latter two classes of MCSs experience isentropic lifting in the southwesterly warm and moist flows. They all develop in large-scale environments with favorable quasi-geostrophic forcing, albeit weak. Conceptual models are finally developed to facilitate our understanding and prediction of the WSHR events over South China. Full article

(This article belongs to the Special Issue Improving the Understanding, Diagnostics, and Prediction of Precipitation)

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22 pages, 2141 KiB

Open AccessEditor’s ChoiceReview

Air Pollution and the Airways: Lessons from a Century of Human Urbanization

by Janne Goossens, Anne-Charlotte Jonckheere, Lieven J. Dupont and Dominique M. A. Bullens

Atmosphere 2021, 12(7), 898; https://doi.org/10.3390/atmos12070898 - 11 Jul 2021

Cited by 17 | Viewed by 5800

Abstract

Since the industrial revolution, air pollution has become a major problem causing several health problems involving the airways as well as the cardiovascular, reproductive, or neurological system. According to the WHO, about 3.6 million deaths every year are related to inhalation of polluted [...] Read more.

Since the industrial revolution, air pollution has become a major problem causing several health problems involving the airways as well as the cardiovascular, reproductive, or neurological system. According to the WHO, about 3.6 million deaths every year are related to inhalation of polluted air, specifically due to pulmonary diseases. Polluted air first encounters the airways, which are a major human defense mechanism to reduce the risk of this aggressor. Air pollution consists of a mixture of potentially harmful compounds such as particulate matter, ozone, carbon monoxide, volatile organic compounds, and heavy metals, each having its own effects on the human body. In the last decades, a lot of research investigating the underlying risks and effects of air pollution and/or its specific compounds on the airways, has been performed, involving both in vivo and in vitro experiments. The goal of this review is to give an overview of the recent data on the effects of air pollution on healthy and diseased airways or models of airway disease, such as asthma or chronic obstructive pulmonary disease. Therefore, we focused on studies involving pollution and airway symptoms and/or damage both in mice and humans. Full article

(This article belongs to the Special Issue Air Pollution and Public Health Effects)

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21 pages, 13778 KiB

Open AccessEditor’s ChoiceArticle

Impacts of Non-Local versus Local Moisture Sources on a Heavy (and Deadly) Rain Event in Israel

by Barry Lynn, Yoav Yair, Yoav Levi, Shlomi Ziskin Ziv, Yuval Reuveni and Alexander Khain

Atmosphere 2021, 12(7), 855; https://doi.org/10.3390/atmos12070855 - 30 Jun 2021

Cited by 3 | Viewed by 1890

Abstract

Motivated by poor forecasting of a deadly convective event within the Levant, the factor separation technique was used to investigate the impact of non-local versus local moisture sources on simulated precipitation and lightning rates in central and southern Israel on 25 and 26 [...] Read more.

Motivated by poor forecasting of a deadly convective event within the Levant, the factor separation technique was used to investigate the impact of non-local versus local moisture sources on simulated precipitation and lightning rates in central and southern Israel on 25 and 26 April 2018. Both days saw unusually heavy rains, and it was hypothesized that antecedent precipitation on 25 April contributed to the development of deadly flooding late morning on the 26th, as well as strong lightning and heavy rains later the same day. Antecedent precipitation led to an increase in the precipitable water content and an overall increase in instability as measured by the Convective Available Potential Energy (CAPE). The deadly flood occurred in the area of the Tzafit river gorge (hereafter, Tzafit river), about 25 km southeast of the city of Dimona, a semi-arid region in the northeastern Negev desert. The heavy rains and strong lightning occurred throughout the Levant with local peaks in the vicinity of Jerusalem. Factor separation conducted in model simulations showed that local ground moisture sources had a large impact on the CAPE and subsequent precipitation and lightning rates in the area of Jerusalem, while non-local moisture sources enabled weak convection to occur over broad areas, with particularly strong convection in the area of the Tzafit river. The coupled impact of both moisture sources also led to localized enhanced areas of convective activity. The results suggest that forecast models for the Levant should endeavor to incorporate an accurate depiction of soil moisture to predict convective rain, especially during the typically drier spring-time season. Full article

(This article belongs to the Special Issue Satellites Applied in Extreme Weather and Their Atmospheric Mechanisms)

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29 pages, 12471 KiB

Open AccessEditor’s ChoiceArticle

Evaluating the Impact of a Wall-Type Green Infrastructure on PM₁₀ and NOx Concentrations in an Urban Street Environment

by Maria Gabriella Villani, Felicita Russo, Mario Adani, Antonio Piersanti, Lina Vitali, Gianni Tinarelli, Luisella Ciancarella, Gabriele Zanini, Antonio Donateo, Matteo Rinaldi, Claudio Carbone, Stefano Decesari and Peter Sänger

Atmosphere 2021, 12(7), 839; https://doi.org/10.3390/atmos12070839 - 29 Jun 2021

Cited by 10 | Viewed by 4200

Abstract

Nature-based solutions can represent beneficial tools in the field of urban transformation for their contribution to important environmental services such as air quality improvement. To evaluate the impact on urban air pollution of a CityTree (CT), an innovative wall-type green infrastructure in passive [...] Read more.

Nature-based solutions can represent beneficial tools in the field of urban transformation for their contribution to important environmental services such as air quality improvement. To evaluate the impact on urban air pollution of a CityTree (CT), an innovative wall-type green infrastructure in passive (deposition) and active (filtration) modes of operation, a study was conducted in a real urban setting in Modena (Italy) during 2017 and 2018, combining experimental measurements with modelling system evaluations. In this work, relying on the computational resources of CRESCO (Computational Centre for Research on Complex Systems)/ENEAGRID High Performance Computing infrastructure, we used the air pollution microscale model PMSS (Parallel Micro-SWIFT-Micro SPRAY) to simulate air quality during the experimental campaigns. The spatial characteristics of the impact of the CT on local air pollutants concentrations, specifically nitrogen oxides (NOx) and particulate matter (PM₁₀), were assessed. In particular, we used prescribed bulk deposition velocities provided by the experimental campaigns, which tested the CT both in passive (deposition) and in active (filtration) mode of operation. Our results showed that the PM₁₀ and NOx concentration reductions reach from more than 0.1% up to about 0.8% within an area of 10 × 20 m² around the infrastructure, when the green infrastructure operates in passive mode. In filtration mode the CT exhibited higher performances in the abatement of PM₁₀ concentrations (between 1.5% and 15%), within approximately the same area. We conclude that CTs may find an application in air quality hotspots within specific urban settings (i.e., urban street canyons) where a very localized reduction of pollutants concentration during rush hours might be of interest to limit population exposure. The optimization of the spatial arrangement of CT modules to increment the “clean air zone” is a factor to be investigated in the ongoing development of the CT technology. Full article

(This article belongs to the Special Issue High Performance Computing Serving Atmospheric Transport & Dispersion Modelling)

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13 pages, 3626 KiB

Open AccessEditor’s ChoiceArticle

Possible Associations between the Number of Cold Days over East Asia and Arctic Oscillation and Arctic Warming

by Wei Song and Xiaochen Ye

Atmosphere 2021, 12(7), 842; https://doi.org/10.3390/atmos12070842 - 29 Jun 2021

Cited by 2 | Viewed by 1669

Abstract

Based on the NECP/NCAR reanalysis dataset, the associations between the number of cold days (NCD) over East Asia (100–150° E, 25–55° N) and Arctic Oscillation (AO)/Arctic warming during 1956–2015 are explored. The results show the NCD was closely associated with AO during 1956–1990 [...] Read more.

Based on the NECP/NCAR reanalysis dataset, the associations between the number of cold days (NCD) over East Asia (100–150° E, 25–55° N) and Arctic Oscillation (AO)/Arctic warming during 1956–2015 are explored. The results show the NCD was closely associated with AO during 1956–1990 and Arctic warming during 1991–2015. It reveals NCD over East Asia showed a downward trend and a significantly negative correlation with AO in the previous stage, while it presented an upward trend and notably positive association with Arctic warming in the later period. Meanwhile the increase in the earlier-stage AO will often be accompanied by the weakness of the Siberian high (SH), the Ural Mountains Blocking high (UBH), and the East Asian trough (EAT), and a “positive–negative–positive” wave band exist in the upper troposphere, which is linked with weakened northerly wind over East Asia. All these anomalies are unfavorable for the southward transportation of cold air, eventually leading to the decrease in NCD over East Asia. Additionally, when the near-surface temperature over the Arctic rises in the later period, on the one hand, SH reinforces and further results in more NCD over East Asia; on the other hand, the 1000–500 hPa thickness field displays a “north positive–south negative” pattern, which is conducive to the deceleration of the westerlies at mid-latitudes over Eurasia, and further bring about the enhancement of EAT and UBH, favoring the southward intrusion of cold air, finally, more NCD are generated. Full article

(This article belongs to the Special Issue Asia-Pacific Region: Monsoons and Typhoons)

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28 pages, 10311 KiB

Open AccessEditor’s ChoiceArticle

Relationship between Early-Stage Features and Lifetime Maximum Intensity of Tropical Cyclones over the Western North Pacific

by Ren Lu and Xiaodong Tang

Atmosphere 2021, 12(7), 815; https://doi.org/10.3390/atmos12070815 - 24 Jun 2021

Cited by 2 | Viewed by 3105

Abstract

The relationship between early-stage features and lifetime maximum intensity (LMI) of tropical cyclones (TCs) over the Western North Pacific (WNP) was investigated by ensemble machine learning methods and composite analysis in this study. By selecting key features of TCs’ vortex attributes and environmental [...] Read more.

The relationship between early-stage features and lifetime maximum intensity (LMI) of tropical cyclones (TCs) over the Western North Pacific (WNP) was investigated by ensemble machine learning methods and composite analysis in this study. By selecting key features of TCs’ vortex attributes and environmental conditions, a two-step AdaBoost model demonstrated accuracy of about 75% in distinguishing weak and strong TCs at genesis and a coefficient of determination (

R^{2}

) of 0.30 for LMI estimation from the early stage of strong TCs, suggesting an underlying relationship between LMI and early-stage features. The composite analysis reveals that TCs with higher LMI are characterized by lower latitude embedded in a continuous band of high low-troposphere vorticity, more compact circulation at both the upper and lower levels of the troposphere, stronger circulation at the mid-troposphere, a higher outflow layer with stronger convection, a more symmetrical structure of high-level moisture distribution, a slower translation speed, and a greater intensification rate around genesis. Specifically, TCs with greater “tightness” at genesis may have a better chance of strengthening to major TCs (LMI ≥ 96 kt), since it represents a combination of the inner and outer-core wind structure related to TCs’ rapid intensification and eyewall replacement cycle. Full article

(This article belongs to the Special Issue Rapid Intensity Changes of Tropical Cyclones)

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22 pages, 2578 KiB

Open AccessEditor’s ChoiceArticle

Spatial Regression Modeling Approach for Assessing the Spatial Variation of Air Pollutants

by Seunghoon Park and Dongwon Ko

Atmosphere 2021, 12(6), 785; https://doi.org/10.3390/atmos12060785 - 18 Jun 2021

Cited by 7 | Viewed by 2875

Abstract

Over the past decades, industrialization has resulted in radical economic development in Korea. The resulting urban sprawl and unsustainable development have led to considerable air pollution. In this study, using spatial regression models, we examine the effects of the physical and socioeconomic characteristics [...] Read more.

Over the past decades, industrialization has resulted in radical economic development in Korea. The resulting urban sprawl and unsustainable development have led to considerable air pollution. In this study, using spatial regression models, we examine the effects of the physical and socioeconomic characteristics of neighborhoods on particulate matter (PM₁₀, PM_2.5), NO₂, CO, and SO₂ concentrations in the Daegu Metropolitan area. Results reveal the following: (i) the socioeconomic characteristics were not statistically significant regardless of the air pollutant type; (ii) the effects of the built environment characteristics of the neighborhoods were different for each air pollutant. Compared with other pollutants, PM_2.5 was affected more by the built environment. Concerning the neighborhoods’ main roads, the SO₂ concentration was higher, that of PM_2.5 was higher in neighborhoods with more bus stops, and those of CO and PM_2.5 were possibly higher in the neighborhood of industrial zones. In neighborhoods with parks and green areas, air pollutant concentrations are likely to be lower. When the total used surface of residential buildings was higher, the air pollutant concentrations were lower. Contextually, similar neighborhoods with more single-family houses seemed to have high pollution levels. Overall, this study is expected to guide policymakers and planners in making smart decisions for eco-friendly and healthy cities. Full article

(This article belongs to the Special Issue Regional Air Quality Modeling)

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11 pages, 9979 KiB

Open AccessEditor’s ChoiceArticle

A Cluster Analysis of Forward Trajectory to Identify the Transport Pathway of Salt-Dust Particles from Dried Bottom of Aral Sea, Central Asia

by Aishajiang Aili, Jilili Abuduwaili, Hailiang Xu, Xinfeng Zhao and Xinghong Liu

Atmosphere 2021, 12(6), 764; https://doi.org/10.3390/atmos12060764 - 13 Jun 2021

Cited by 6 | Viewed by 3083

Abstract

The Aral Sea basin is the most active source of salt-dust storms in the central Asian region, while its exposed bottom is acting as a “distributer” of salts and chemicals over the adjoining areas. In this study, the Hybrid Single Particle Lagrangian Integrated [...] Read more.

The Aral Sea basin is the most active source of salt-dust storms in the central Asian region, while its exposed bottom is acting as a “distributer” of salts and chemicals over the adjoining areas. In this study, the Hybrid Single Particle Lagrangian Integrated Trajectory Model (HYSPLIT-4) is used to identify the trajectories of air parcels from the dried bottom of the Aral Sea region (45.40° N, 61.30° E) that are potentially containing salt-dust and their probability of influencing the downwind area in the period of 2016–2020. The frequency of air parcel trajectory was mapped for six levels: 100, 300, 500, 1000, 2000, and 3000 m agl. The trajectories were categorized by k-means clustering into four clusters that are named by their direction of movement as follows: Cluster 1: E category, Cluster 2: NE category, Cluster 3: W category, and the Cluster 4: S category. The 72 h of forward trajectories showed that salt-dust storms starting from the dried bottom of the Aral Sea had the highest probability of affecting the northeastern region e.g., Siberian Plain, followed by the southern region e.g., Iran Plateau. Total number of trajectories within these two clusters (NE and S) accounts for 90% (or 413 days) of trajectories in examined days. The main area of influence of salt-dust is close to the source area. The potential transport distance of salt-dust particles increases with the height of the starting point. The surface wind, which results from the changes of the Siberian High (SH), has a major role in shaping the surface atmospheric circulation which determines the transport pathway of salt-dust particles over the Aral Sea region. The results of this study could be useful to forecast the potential occurrence of salt-dust storms in downwind affected areas and would also be helpful to understand the possible causes of salt-dust storms which can provide the scientific basis for mitigation of the negative impact of salt-dust storms on the environment and human health. Further research should be conducted by using monitoring data to confirm the deposition of dust and salt particles in those areas mapped by our study. Full article

(This article belongs to the Section Atmospheric Techniques, Instruments, and Modeling)

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19 pages, 4601 KiB

Open AccessEditor’s ChoiceArticle

Effectiveness of Tree Pattern in Street Canyons on Thermal Conditions and Human Comfort. Assessment of an Urban Renewal Project in Historical District in Lodz (Poland)

by Anna Dominika Bochenek and Katarzyna Klemm

Atmosphere 2021, 12(6), 751; https://doi.org/10.3390/atmos12060751 - 10 Jun 2021

Cited by 13 | Viewed by 3135

Abstract

The implementation of adaptation strategies has become an essential activity of spatial planning departments. Passive technologies related to the introduction of natural components in the form of vegetation are used, especially in urban development plans, to mitigate the effects of climate change and [...] Read more.

The implementation of adaptation strategies has become an essential activity of spatial planning departments. Passive technologies related to the introduction of natural components in the form of vegetation are used, especially in urban development plans, to mitigate the effects of climate change and thus improve the quality of citizen life. Nature-Based Solutions are of particular importance in the areas of strict city centers, where historical building structures are subject to legal protection. In this study, the authors tested the influence of high greenery on the microclimatic conditions in the areas of typical street canyons (east–west and north–south orientations). Authors included the established greenery strategy by the City Planning Department. To estimate the impact of the assumed scenarios, a CFD tool was used—the ENVI-met application, which is commonly used in the field of urban microclimatology. Studies have shown that the introduction of 10% of green area contributed to a maximum air temperature reduction of 0.80 °C (17:00) in an east–west-oriented canyon, 0.49 °C (10:00) in a north–south canyon. The scenarios, assumed by the City Planning Department, related to the introduction of a greater amount of greenery turned out to be a less effective solution. The impact of greenery on the thermal comfort felt by humans was also determined. The reduction in the PET index was a maximum of 10.80 °C (14:00) in an east–west canyon; 6.66 °C (14:00) in a canyon area with a north–south orientation. This research might constitute the foundations to a re-evaluation of the urban development plans. The outcomes can lead to taking alternative direction of city layout transformations. Full article

(This article belongs to the Special Issue The Role of Urban Vegetation Management and Planning in Climate Change Adaptation Strategies)

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15 pages, 9339 KiB

Open AccessEditor’s ChoiceArticle

Seasonal to Interannual Variability of Vertical Wind Shear and Its Relationship with Tropical Cyclogenesis in the Mozambique Channel

by Atanásio João Manhique, Isac Arnaldo Guirrugo, Bernardino João Nhantumbo and Alberto Francisco Mavume

Atmosphere 2021, 12(6), 739; https://doi.org/10.3390/atmos12060739 - 9 Jun 2021

Cited by 2 | Viewed by 2970

Abstract

This article explores the relationship between vertical wind shear (VWS) and tropical cyclone (TC) genesis in the Mozambique Channel (MC) for the period 1979–2019. Additionally, SST, low-level relative vorticity, 700 hPa relative humidity and upper-level divergence were also analyzed for the peak cyclogenesis [...] Read more.

This article explores the relationship between vertical wind shear (VWS) and tropical cyclone (TC) genesis in the Mozambique Channel (MC) for the period 1979–2019. Additionally, SST, low-level relative vorticity, 700 hPa relative humidity and upper-level divergence were also analyzed for the peak cyclogenesis months to explore their relative contributions. The analyses were done using NCEP/NCAR Reanalysis-1 for the atmospheric fields, monthly Optimum Interpolation SST V2, and for the cyclogenesis the TC best track data from the La Reunion–Regional Specialized Meteorological and Joint Typhoon Warning Centre. A total of 43 TCs generated in the MC were observed for the analysed period. The maximum frequency of cyclogenesis in the MC was observed during January and February and the spatial location of maximum TC genesis was coincident with the minimum values of the VWS. The VWS showed significant correlations with TC intensity, particularly when considering the upper atmosphere (200–500 hPa) or the bulk (200–850 hPa) VWS. The mean composites of the cyclogenesis months over the MC of SST, relative humidity at 700 hPa, divergence at upper atmosphere, showed significant values. However, linear correlations between these factors vs. TC genesis frequency and intensity were not significant. Analyses of interannual correlations between VWS and Niño-3.4 (subtropical southwest Indian Ocean dipole-SIOD) showed statistically significant positive (negative) correlations at different lags, suggesting that La Niña and the positive phase of SIOD conditions are favorable to weaker VWS and thus to intensification of TCs in the Mozambique Channel. Thirteen landfall cases were observed with seven over the Madagascar west coast and six over the Mozambique coast. The landfall over the Madagascar (Mozambique) coast was associated with strengthened (weakened) VWS. Full article

(This article belongs to the Special Issue Tropical Cyclones in the Indian Ocean)

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12 pages, 1375 KiB

Open AccessEditor’s ChoiceArticle

Climate Change Impacts on Temperature and Chill Unit Trends for Apple (Malus domestica) Production in Ceres, South Africa

by Phumudzo Charles Tharaga, Abraham Stephanus Steyn and Gesine Maria Coetzer

Atmosphere 2021, 12(6), 740; https://doi.org/10.3390/atmos12060740 - 9 Jun 2021

Cited by 2 | Viewed by 4496

Abstract

Climate is an essential part of crop production, determining the suitability of a given region for deciduous fruit products such as apples (Malus domestica). It influences the yield and quality of fruits. There is strong evidence of global and regional-scale climate [...] Read more.

Climate is an essential part of crop production, determining the suitability of a given region for deciduous fruit products such as apples (Malus domestica). It influences the yield and quality of fruits. There is strong evidence of global and regional-scale climate change since the advent of the industrial era. In South Africa, mean surface temperatures have revealed a warming trend over the last century. This study aimed to assess the impact of climate change on temperature and chill unit trends for apple production in Ceres, South Africa. The daily positive Utah chill units (DPCU) model was used as frequent high temperatures can lead to a high negation volume. Historically observed (1981–2010) and future projected (2011–2100) temperatures were obtained from the South African Weather Service (SAWS) and three ensemble members of the Cubic-Conformal Atmospheric Model (CCAM), respectively. The latter employed the RCP8.5 pathway. Linear trends were calculated for temperature and accumulated PCUs for the historical base period. The probability of accumulating specific threshold PCU values for both historical and future periods was assessed from cumulative distribution functions (CDFs). The historical change in minimum temperatures showed no significant trend. Ceres revealed a warming trend in maximum temperatures over the historical period. By the 2080s, the probability of not exceeding a threshold of 1600 PCUs was exceptionally high for all ensemble members. Future projections showed a decline in the accumulated PCUs of 2–5% by the 2020s, 7–17% by the 2050s, and 20–34% towards the end of the 20th century. Based on these results, it is clear that winter chill units are negatively influenced by climate change. The loss in yield and fruit quality of apples due to climate change can negatively impact the export market, leading to significant economic losses for apple production in the Ceres area. Full article

(This article belongs to the Special Issue Meteorological Conditions of Temperate Zone Fruit Production)

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38 pages, 21415 KiB

Open AccessEditor’s ChoiceArticle

ECLand: The ECMWF Land Surface Modelling System

by Souhail Boussetta, Gianpaolo Balsamo, Gabriele Arduini, Emanuel Dutra, Joe McNorton, Margarita Choulga, Anna Agustí-Panareda, Anton Beljaars, Nils Wedi, Joaquín Munõz-Sabater, Patricia de Rosnay, Irina Sandu, Ioan Hadade, Glenn Carver, Cinzia Mazzetti, Christel Prudhomme, Dai Yamazaki and Ervin Zsoter

Atmosphere 2021, 12(6), 723; https://doi.org/10.3390/atmos12060723 - 5 Jun 2021

Cited by 28 | Viewed by 8458

Abstract

The land-surface developments of the European Centre for Medium-range Weather Forecasts (ECMWF) are based on the Carbon-Hydrology Tiled Scheme for Surface Exchanges over Land (CHTESSEL) and form an integral part of the Integrated Forecasting System (IFS), supporting a wide range of global weather, [...] Read more.

The land-surface developments of the European Centre for Medium-range Weather Forecasts (ECMWF) are based on the Carbon-Hydrology Tiled Scheme for Surface Exchanges over Land (CHTESSEL) and form an integral part of the Integrated Forecasting System (IFS), supporting a wide range of global weather, climate and environmental applications. In order to structure, coordinate and focus future developments and benefit from international collaboration in new areas, a flexible system named ECLand, which would facilitate modular extensions to support numerical weather prediction (NWP) and society-relevant operational services, for example, Copernicus, is presented. This paper introduces recent examples of novel ECLand developments on (i) vegetation; (ii) snow; (iii) soil; (iv) open water/lake; (v) river/inundation; and (vi) urban areas. The developments are evaluated separately with long-range, atmosphere-forced surface offline simulations and coupled land-atmosphere-ocean experiments. This illustrates the benchmark criteria for assessing both process fidelity with regards to land surface fluxes and reservoirs of the water-energy-carbon exchange on the one hand, and on the other hand the requirements of ECMWF’s NWP, climate and atmospheric composition monitoring services using an Earth system assimilation and prediction framework. Full article

(This article belongs to the Special Issue Representation of Land Surface Processes in Weather and Climate Models)

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13 pages, 2281 KiB

Open AccessEditor’s ChoiceArticle

Metal(Loids) Bioaccessibility in Road Dust from the Surrounding Villages of an Active Mine

by Carla Candeias, Paula F. Ávila, Eduardo Ferreira da Silva and Fernando Rocha

Atmosphere 2021, 12(6), 685; https://doi.org/10.3390/atmos12060685 - 27 May 2021

Cited by 5 | Viewed by 3255

Abstract

Human activities, in general, cause a significant impact on the environment and human health. The present study aims to characterize the road dust of villages located near an active mine and to assess metal(loids) bioaccessible fractions. From the collected road dust samples (<250 [...] Read more.

Human activities, in general, cause a significant impact on the environment and human health. The present study aims to characterize the road dust of villages located near an active mine and to assess metal(loids) bioaccessible fractions. From the collected road dust samples (<250 µm fraction), the pseudo total, gastric (G) and gastrointestinal (GI) phase (UBM assay) concentrations, mineralogical composition, enrichment factor (EF), and risk for humans were determined. The obtained results revealed that arsenic represents the highest risk to humans, with mean pseudototal values higher than the maximum reference value range. The enrichment factor pointed to As as having significant to very high enrichment in all of the villages. In addition, Cd presented the maximum EF values in all of the villages, and was thus classified as having a very high enrichment. Particles enriched in As, Ca, Fe, Cu, Al, and Ti were identified by SEM-EDS in weathered agglomerates, and were linked to mine wastes and long-distance transport through both wind and/or traffic. The arsenic bioaccessibility fraction (%BAF) presented low values in the studied samples, possibly because of the low complex solubility of Fe with adsorbed As, limiting the release of arsenic and reducing its bioaccessibility. The concentrations of bioaccessible Cd for the G and GI phases were within the reference range, while for Cu, they were above and for Pb they were lower than the reference value range. The results show that the pseudototal fraction risk is overestimated when compared with BAF%; nevertheless, the total G and GI risks were above the carcinogenic target risk (1 × 10⁻⁶) in most of the samples. The carcinogenic risk of the bioaccessible contaminants showed that As represented the higher risk for developing cancer over a lifetime, with ingestion being the main risk route. Full article

(This article belongs to the Collection Measurement of Exposure to Air Pollution)

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18 pages, 1287 KiB

Open AccessEditor’s ChoiceReview

Deposition of Aerosols onto Upper Ocean and Their Impacts on Marine Biota

by Andreia Ventura, Eliana F. C. Simões, Antoine S. Almeida, Roberto Martins, Armando C. Duarte, Susana Loureiro and Regina M. B. O. Duarte

Atmosphere 2021, 12(6), 684; https://doi.org/10.3390/atmos12060684 - 27 May 2021

Cited by 17 | Viewed by 7955

Abstract

Atmospheric aerosol deposition (wet and dry) is an important source of macro and micronutrients (N, P, C, Si, and Fe) to the oceans. Most of the mass flux of air particles is made of fine mineral particles emitted from arid or semi-arid areas [...] Read more.

Atmospheric aerosol deposition (wet and dry) is an important source of macro and micronutrients (N, P, C, Si, and Fe) to the oceans. Most of the mass flux of air particles is made of fine mineral particles emitted from arid or semi-arid areas (e.g., deserts) and transported over long distances until deposition to the oceans. However, this atmospheric deposition is affected by anthropogenic activities, which heavily impacts the content and composition of aerosol constituents, contributing to the presence of potentially toxic elements (e.g., Cu). Under this scenario, the deposition of natural and anthropogenic aerosols will impact the biogeochemical cycles of nutrients and toxic elements in the ocean, also affecting (positively or negatively) primary productivity and, ultimately, the marine biota. Given the importance of atmospheric aerosol deposition to the oceans, this paper reviews the existing knowledge on the impacts of aerosol deposition on the biogeochemistry of the upper ocean, and the different responses of marine biota to natural and anthropogenic aerosol input. Full article

(This article belongs to the Special Issue Feature Papers of Aerosol Impacts on Climate and Air Quality)

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16 pages, 6544 KiB

Open AccessEditor’s ChoiceArticle

Characterisation of Extreme Precipitation Events in the Pyrenees: From the Local to the Synoptic Scale

by Marc Lemus-Canovas, Joan Albert Lopez-Bustins, Javier Martín-Vide, Amar Halifa-Marin, Damián Insua-Costa, Joan Martinez-Artigas, Laura Trapero, Roberto Serrano-Notivoli and José María Cuadrat

Atmosphere 2021, 12(6), 665; https://doi.org/10.3390/atmos12060665 - 22 May 2021

Cited by 10 | Viewed by 3993

Abstract

Mountain systems within the Mediterranean region, e.g., the Pyrenees, are very sensitive to climate change. In the present study, we quantified the magnitude of extreme precipitation events and the number of days with torrential precipitation (daily precipitation ≥ 100 mm) in all the [...] Read more.

Mountain systems within the Mediterranean region, e.g., the Pyrenees, are very sensitive to climate change. In the present study, we quantified the magnitude of extreme precipitation events and the number of days with torrential precipitation (daily precipitation ≥ 100 mm) in all the rain gauges available in the Pyrenees for the 1981–2015 period, analyzing the contribution of the synoptic scale in this type of event. The easternmost (under Mediterranean influence) and north-westernmost (under Atlantic influence) areas of the Pyrenees registered the highest number of torrential events. The heaviest events are expected in the eastern part, i.e., 400 mm day⁻¹ for a return period of 200 years. Northerly advections over the Iberian Peninsula, which present a low zonal index, i.e., implying a stronger meridional component, give rise to torrential events over the western Pyrenees; and easterly advections favour extreme precipitation over the eastern Pyrenees. The air mass travels a long way, from the east coast of North America, bringing heavy rainfall to the western Pyrenees. In the case of the torrential events over the eastern Pyrenees, the trajectory of the air mass causing the events in these areas is very short and originates in the Mediterranean Basin. The North Atlantic Oscillation (NAO) index has no influence upon the occurrence of torrential events in the Pyrenees, but these events are closely related to certain Mediterranean teleconnections such as the Western Mediterranean Oscillation (WeMO). Full article

(This article belongs to the Special Issue Spatiotemporal Variability of Precipitation Concentration and Drought Events in the Mediterranean Basin)

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19 pages, 2383 KiB

Open AccessEditor’s ChoiceArticle

Potential Human and Plant Pathogenic Species in Airborne PM10 Samples and Relationships with Chemical Components and Meteorological Parameters

by Salvatore Romano, Mattia Fragola, Pietro Alifano, Maria Rita Perrone and Adelfia Talà

Atmosphere 2021, 12(5), 654; https://doi.org/10.3390/atmos12050654 - 20 May 2021

Cited by 6 | Viewed by 3212

Abstract

A preliminary local database of potential (opportunistic) airborne human and plant pathogenic and non-pathogenic species detected in PM10 samples collected in winter and spring is provided, in addition to their seasonal dependence and relationships with meteorological parameters and PM10 chemical species. The PM10 [...] Read more.

A preliminary local database of potential (opportunistic) airborne human and plant pathogenic and non-pathogenic species detected in PM10 samples collected in winter and spring is provided, in addition to their seasonal dependence and relationships with meteorological parameters and PM10 chemical species. The PM10 samples, collected at a Central Mediterranean coastal site, were analyzed by the 16S rRNA gene metabarcoding approach, and Spearman correlation coefficients and redundancy discriminant analysis tri-plots were used to investigate the main relationships. The screening of 1187 detected species allowed for the detection of 76 and 27 potential (opportunistic) human and plant pathogens, respectively. The bacterial structure of both pathogenic and non-pathogenic species varied from winter to spring and, consequently, the inter-species relationships among potential human pathogens, plant pathogens, and non-pathogenic species varied from winter to spring. Few non-pathogenic species and even fewer potential human pathogens were significantly correlated with meteorological parameters, according to the Spearman correlation coefficients. Conversely, several potential plant pathogens were strongly and positively correlated with temperature and wind speed and direction both in winter and in spring. The number of strong relationships between presumptive (human and plant) pathogens and non-pathogens, and meteorological parameters slightly increased from winter to spring. The sample chemical composition also varied from winter to spring. Some potential human and plant pathogens were correlated with chemicals mainly associated with marine aerosol and/or with soil dust, likely because terrestrial and aquatic environments were the main habitats of the detected bacterial species. The carrier role on the species seasonal variability was also investigated. Full article

(This article belongs to the Special Issue Bioaerosols: Composition, Meteorological Impact, and Transport)

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36 pages, 57857 KiB

Open AccessEditor’s ChoiceReview

Recent Advances in Our Understanding of Tropical Cyclone Intensity Change Processes from Airborne Observations

by Robert F. Rogers

Atmosphere 2021, 12(5), 650; https://doi.org/10.3390/atmos12050650 - 19 May 2021

Cited by 17 | Viewed by 5553

Abstract

Recent (past ~15 years) advances in our understanding of tropical cyclone (TC) intensity change processes using aircraft data are summarized here. The focus covers a variety of spatiotemporal scales, regions of the TC inner core, and stages of the TC lifecycle, from preformation [...] Read more.

Recent (past ~15 years) advances in our understanding of tropical cyclone (TC) intensity change processes using aircraft data are summarized here. The focus covers a variety of spatiotemporal scales, regions of the TC inner core, and stages of the TC lifecycle, from preformation to major hurricane status. Topics covered include (1) characterizing TC structure and its relationship to intensity change; (2) TC intensification in vertical shear; (3) planetary boundary layer (PBL) processes and air–sea interaction; (4) upper-level warm core structure and evolution; (5) genesis and development of weak TCs; and (6) secondary eyewall formation/eyewall replacement cycles (SEF/ERC). Gaps in our airborne observational capabilities are discussed, as are new observing technologies to address these gaps and future directions for airborne TC intensity change research. Full article

(This article belongs to the Special Issue Rapid Intensity Changes of Tropical Cyclones)

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15 pages, 7600 KiB

Open AccessEditor’s ChoiceArticle

Accelerated Time and High-Resolution 3D Modeling of the Flow and Dispersion of Noxious Substances over a Gigantic Urban Area—The EMERGENCIES Project

by Olivier Oldrini, Patrick Armand, Christophe Duchenne, Sylvie Perdriel and Maxime Nibart

Atmosphere 2021, 12(5), 640; https://doi.org/10.3390/atmos12050640 - 18 May 2021

Cited by 4 | Viewed by 2457

Abstract

Accidental or malicious releases in the atmosphere are more likely to occur in built-up areas, where flow and dispersion are complex. The EMERGENCIES project aims to demonstrate the operational feasibility of three-dimensional simulation as a support tool for emergency teams and first responders. [...] Read more.

Accidental or malicious releases in the atmosphere are more likely to occur in built-up areas, where flow and dispersion are complex. The EMERGENCIES project aims to demonstrate the operational feasibility of three-dimensional simulation as a support tool for emergency teams and first responders. The simulation domain covers a gigantic urban area around Paris, France, and uses high-resolution metric grids. It relies on the PMSS modeling system to model the flow and dispersion over this gigantic domain and on the Code_Saturne model to simulate both the close vicinity and the inside of several buildings of interest. The accelerated time is achieved through the parallel algorithms of the models. Calculations rely on a two-step approach: the flow is computed in advance using meteorological forecasts, and then on-demand release scenarios are performed. Results obtained with actual meteorological mesoscale data and realistic releases occurring both inside and outside of buildings are presented and discussed. They prove the feasibility of operational use by emergency teams in cases of atmospheric release of hazardous materials. Full article

(This article belongs to the Special Issue High Performance Computing Serving Atmospheric Transport & Dispersion Modelling)

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23 pages, 93677 KiB

Open AccessEditor’s ChoiceArticle

Exposure Assessment of Climate Extremes over the Europe–Mediterranean Region

by Mehmet Barış Kelebek, Fulden Batibeniz and Barış Önol

Atmosphere 2021, 12(5), 633; https://doi.org/10.3390/atmos12050633 - 17 May 2021

Cited by 18 | Viewed by 4455

Abstract

The use of a compact set of climate change indexes enhances our understanding of the combined impacts of extreme climatic conditions. In this study, we developed the modified Climate Extremes Index (mCEI) to obtain unified information about different types of extremes. For this [...] Read more.

The use of a compact set of climate change indexes enhances our understanding of the combined impacts of extreme climatic conditions. In this study, we developed the modified Climate Extremes Index (mCEI) to obtain unified information about different types of extremes. For this purpose, we calculated 10 different climate change indexes considering the temperature extremes, extreme precipitation, and moisture surplus and drought over the Europe–Mediterranean (EURO–MED) region for the 1979–2016 period. As a holistic approach, mCEI provides spatiotemporal information, and the high-resolution grid-based data allow us to accomplish detailed country-based and city-based analyses. The analyses indicate that warm temperature extremes rise significantly over the EURO–MED region at a rate of 1.9% decade⁻¹, whereas the cold temperature extremes decrease. Extreme drought has a significant increasing trend of 3.8% decade⁻¹. Although there are regional differences, extreme precipitation indexes have a significant increasing tendency. According to the mCEI, the major hotspots for the combined extremes are the Mediterranean coasts, the Balkan countries, Eastern Europe, Iceland, western Russia, western Turkey, and western Iraq. The decadal changes of mCEI for these regions are in the range of 3–5% decade⁻¹. The city-scale analysis based on urbanized locations reveals that Fes (Morocco), Izmir (Turkey), Marseille and Aix-en-Provence (France), and Tel Aviv (Israel) have the highest increasing trend of mCEI, which is greater than 3.5% decade⁻¹. Full article

(This article belongs to the Special Issue Extreme Weather Events and Geo-Climatic Hazards Under a Changing Climate)

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13 pages, 19913 KiB

Open AccessEditor’s ChoiceArticle

Human Health Risk Assessment of Air Pollution in the Regions of Unsustainable Heating Sources. Case Study—The Tourist Areas of Southern Poland

by Agnieszka Gruszecka-Kosowska, Jacek Dajda, Ewa Adamiec, Edeltrauda Helios-Rybicka, Marek Kisiel-Dorohinicki, Radosław Klimek, Dariusz Pałka and Jarosław Wąs

Atmosphere 2021, 12(5), 615; https://doi.org/10.3390/atmos12050615 - 10 May 2021

Cited by 7 | Viewed by 2879

Abstract

Air pollution is one of the main factors affecting human health. Air quality is especially important in the tourist areas developed with facilities for outdoor activities. During the winter season of 2017/2018, the concentrations of particulate matter (PM₁₀, PM_2.5, [...] Read more.

Air pollution is one of the main factors affecting human health. Air quality is especially important in the tourist areas developed with facilities for outdoor activities. During the winter season of 2017/2018, the concentrations of particulate matter (PM₁₀, PM_2.5, PM₁), CO, O₃, and NO₂ were studied in 12 attractive tourist villages in the surroundings of the Czorsztyn Reservoir in southern Poland. Air pollutant measurements were performed continuously, using a single ground-based Alphasense air sensor. Our assessment of human health risk (HHRA), arising from inhalation exposure to air contaminants, was calculated for both local inhabitants and tourists, based on actual measured values. It was found that pollutant concentrations exceeded both permissible and recommended levels of PM₁₀ and PM_2.5. The mean total noncarcinogenic risk values were equal to 9.58 (unitless) for adults and 9.68 (unitless) for children and infants, under the resident exposure scenario. However, under the tourist exposure scenario, the mean total risk was equal to 1.63 (unitless) for adults and 1.64 (unitless) for children and infants. The risk to tourists was lower than that to inhabitants due to shorter exposure times. The target non-carcinogenic value of 1, calculated for PM₁₀, PM_2.5, and NO₂, was significantly exceeded in total risk, under the residential exposure scenario, in reference to all the local subpopulations. In the majority of the investigated locations, the total risk exceeded the value of 1, under the tourist scenario, for all the subpopulations analysed. PM_2.5 was recognised to be the most important contaminant in our risk analysis, in view of its share in the total risk value. Full article

(This article belongs to the Special Issue Air Pollution, Air Quality and Human Health)

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27 pages, 4702 KiB

Open AccessEditor’s ChoiceArticle

Aerosol and Cloud Detection Using Machine Learning Algorithms and Space-Based Lidar Data

by John E. Yorks, Patrick A. Selmer, Andrew Kupchock, Edward P. Nowottnick, Kenneth E. Christian, Daniel Rusinek, Natasha Dacic and Matthew J. McGill

Atmosphere 2021, 12(5), 606; https://doi.org/10.3390/atmos12050606 - 7 May 2021

Cited by 23 | Viewed by 5723

Abstract

Clouds and aerosols play a significant role in determining the overall atmospheric radiation budget, yet remain a key uncertainty in understanding and predicting the future climate system. In addition to their impact on the Earth’s climate system, aerosols from volcanic eruptions, wildfires, man-made [...] Read more.

Clouds and aerosols play a significant role in determining the overall atmospheric radiation budget, yet remain a key uncertainty in understanding and predicting the future climate system. In addition to their impact on the Earth’s climate system, aerosols from volcanic eruptions, wildfires, man-made pollution events and dust storms are hazardous to aviation safety and human health. Space-based lidar systems provide critical information about the vertical distributions of clouds and aerosols that greatly improve our understanding of the climate system. However, daytime data from backscatter lidars, such as the Cloud-Aerosol Transport System (CATS) on the International Space Station (ISS), must be averaged during science processing at the expense of spatial resolution to obtain sufficient signal-to-noise ratio (SNR) for accurately detecting atmospheric features. For example, 50% of all atmospheric features reported in daytime operational CATS data products require averaging to 60 km for detection. Furthermore, the single-wavelength nature of the CATS primary operation mode makes accurately typing these features challenging in complex scenes. This paper presents machine learning (ML) techniques that, when applied to CATS data, (1) increased the 1064 nm SNR by 75%, (2) increased the number of layers detected (any resolution) by 30%, and (3) enabled detection of 40% more atmospheric features during daytime operations at a horizontal resolution of 5 km compared to the 60 km horizontal resolution often required for daytime CATS operational data products. A Convolutional Neural Network (CNN) trained using CATS standard data products also demonstrated the potential for improved cloud-aerosol discrimination compared to the operational CATS algorithms for cloud edges and complex near-surface scenes during daytime. Full article

(This article belongs to the Special Issue Lidar Remote Sensing Techniques for Atmospheric Aerosols)

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18 pages, 524 KiB

Open AccessEditor’s ChoiceArticle

On the u_⋆−U Relationship in the Stable Atmospheric Boundary Layer over Arctic Sea Ice

by Dmitry Chechin

Atmosphere 2021, 12(5), 591; https://doi.org/10.3390/atmos12050591 - 2 May 2021

Cited by 3 | Viewed by 2219

Abstract

A relationship between the friction velocity

u_{⋆}

and mean wind speed U in a stable atmospheric boundary layer (ABL) over Arctic sea ice was considered. To that aim, the observations collected during the Surface Heat Budget of the Arctic Ocean (SHEBA) experiment [...] Read more.

A relationship between the friction velocity

u_{⋆}

and mean wind speed U in a stable atmospheric boundary layer (ABL) over Arctic sea ice was considered. To that aim, the observations collected during the Surface Heat Budget of the Arctic Ocean (SHEBA) experiment were used. The observations showed the so-called “hockey-stick” shape of the

u_{⋆} - U

relationship, which consists of a slow increase of

u_{⋆}

with increasing wind speed for

U < U_{t r}

and a more rapid almost linear increase of

u_{⋆}

for

U > U_{t r}

, where

U_{t r}

is the wind speed of transition between the two regimes. Such a relationship is most pronounced at the highest observational levels, namely at 9 and 14 m, and is also sharper when the air-surface temperature difference exceeds its average values for stable conditions. It is shown that the Monin–Obukhov similarity theory (MOST) reproduces the observed

u_{⋆} - U

relationship rather well. This suggests that at least for the SHEBA dataset, there is no contradiction between MOST and the “hockey-stick” shape of the

u_{⋆} - U

relationship. However, the SHEBA data, as well as the single-column simulations show that for cases with strong stability,

u_{⋆}

significantly decreases with height due to the shallowness of the ABL. It was shown that when

u_{⋆}

was assumed independent of height, the value of the normalized drag coefficient, i.e., of the so-called stability correction function for momentum, calculated using observations at a certain level, can be significantly underestimated. To overcome this, the decrease of

u_{⋆}

with height was taken into account in the framework of MOST using local scaling instead of the scaling with surface fluxes. Using such an extended MOST brought the estimates of the normalized drag coefficient closer to the Businger–Dyer relation. Full article

(This article belongs to the Special Issue The Stable Boundary Layer: Observations and Modeling)

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