Editorial

3 pages, 148 KiB

Open AccessEditorial

by Robert D. Brown

Atmosphere 2018, 9(11), 448; https://doi.org/10.3390/atmos9110448 - 15 Nov 2018

Cited by 1 | Viewed by 3445

More than half of the people in the world now live in cities and this proportion is expected to continue to increase. [...] Full article

(This article belongs to the Special Issue Urban Design and City Microclimates)

Research

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26 pages, 10087 KiB

Open AccessArticle

The Street Air Warming Phenomenon in a High-Rise Compact City

by Xiaoxue Wang, Yuguo Li, Xinyan Yang, Pak Wai Chan, Janet Nichol and Qinglan Li

Atmosphere 2018, 9(10), 402; https://doi.org/10.3390/atmos9100402 - 16 Oct 2018

Cited by 10 | Viewed by 4264

Abstract

The street thermal environment is important for thermal comfort, urban climate and pollutant dispersion. A 24-h vehicle traverse study was conducted over the Kowloon Peninsula of Hong Kong in summer, with each measurement period consisting of 2–3 full days. The data covered a [...] Read more.

The street thermal environment is important for thermal comfort, urban climate and pollutant dispersion. A 24-h vehicle traverse study was conducted over the Kowloon Peninsula of Hong Kong in summer, with each measurement period consisting of 2–3 full days. The data covered a total of 158 loops in 198 h along the route on sunny days. The measured data were averaged by three methods (direct average, FFT filter and interpolated by the piecewise cubic Hermite interpolation). The average street air temperatures were found to be 1–3 °C higher than those recorded at nearby fixed weather stations. The street warming phenomenon observed in the study has substantial implications as usually urban heat island (UHI) intensity is estimated from measurement at fixed weather stations, and therefore the UHI intensity in the built areas of the city may have been underestimated. This significant difference is of interest for studies on outdoor air temperature, thermal comfort, urban environment and pollutant dispersion. The differences were simulated by an improved one-dimensional temperature model (ZERO-CAT) using different urban morphology parameters. The model can correct the underestimation of street air temperature. Further sensitivity studies show that the building arrangement in the daytime and nighttime plays different roles for air temperature in the street. City designers can choose different parameters based on their purpose. Full article

(This article belongs to the Special Issue Urban Design and City Microclimates)

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17 pages, 1793 KiB

Open AccessArticle

Outdoor Thermal Comfort during Anomalous Heat at the 2015 Pan American Games in Toronto, Canada

by Alexandria J. Herdt, Robert D. Brown, Ian Scott-Fleming, Guofeng Cao, Melissa MacDonald, Dave Henderson and Jennifer K. Vanos

Atmosphere 2018, 9(8), 321; https://doi.org/10.3390/atmos9080321 - 18 Aug 2018

Cited by 9 | Viewed by 6056

Abstract

Mass sporting events in the summertime are influenced by underlying weather patterns, with high temperatures posing a risk for spectators and athletes alike. To better understand weather variations in the Greater Toronto Area (GTA) during the Pan American Games in 2015 (PA15 Games), [...] Read more.

Mass sporting events in the summertime are influenced by underlying weather patterns, with high temperatures posing a risk for spectators and athletes alike. To better understand weather variations in the Greater Toronto Area (GTA) during the Pan American Games in 2015 (PA15 Games), Environment and Climate Change Canada deployed a mesoscale monitoring network system of 53 weather stations. Spatial maps across the GTA demonstrate large variations by heat metric (e.g., maximum temperature, humidex, and wet bulb globe temperature), identifying Hamilton, Ontario as an area of elevated heat and humidity, and hence risk for heat-related illness. A case study of the Hamilton Soccer Center examined on-site thermal comfort during a heat event and PA15 Soccer Games, demonstrating that athletes and spectators were faced with thermal discomfort and a heightened risk of heat-related illness. Results are corroborated by First Aid and emergency response data during the events, as well as insight from personal experiences and Twitter feed. Integrating these results provides new information on potential benefits to society from utilizing mesonet systems during large-scale sporting events. Results further improve our understanding of intra-urban heat variability and heat-health burden. The benefits of utilizing more comprehensive modeling approaches for human heat stress that coincide with fine-scale weather information are discussed. Full article

(This article belongs to the Special Issue Urban Design and City Microclimates)

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16 pages, 3211 KiB

Open AccessEditor’s ChoiceArticle

Development of a Distributed Modeling Framework to Estimate Thermal Comfort along 2020 Tokyo Olympic Marathon Course

by Satoshi Hirabayashi, Tsutomu Abe, Fumiko Imamura and Chie Morioka

Atmosphere 2018, 9(6), 210; https://doi.org/10.3390/atmos9060210 - 30 May 2018

Cited by 8 | Viewed by 4881

Abstract

Heat stress is an issue for marathon races in the summer, such as the one planned for the 2020 Tokyo Summer Olympic games. The Tokyo Metropolitan Government is planning to grow existing street trees’ canopies to enlarge their shade to reduce air temperature [...] Read more.

Heat stress is an issue for marathon races in the summer, such as the one planned for the 2020 Tokyo Summer Olympic games. The Tokyo Metropolitan Government is planning to grow existing street trees’ canopies to enlarge their shade to reduce air temperature and solar radiation. To formulate a baseline to assess the effect of street trees and buildings on human thermal comfort, Distributed-COMfort FormulA (D-COMFA), a prototype of a distributed computer model using a geographic information system (GIS) was developed. D-COMFA calculates the energy budget of a human body on a 1 m cell basis, using readily available datasets such as weather measurements and polygon data for street structures. D-COMFA was applied to a street segment along the marathon course in Tokyo on an hourly-basis on 9 August 2016, the hottest day in Tokyo in 2016. Our case study showed that the energy budget was positively related to the sky view factor, air temperature, and solar radiation. The energy budget was reduced on average by 26–62% in the shade throughout the day. Full article

(This article belongs to the Special Issue Urban Design and City Microclimates)

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19 pages, 5097 KiB

Open AccessArticle

Evaluation of the ENVI-Met Vegetation Model of Four Common Tree Species in a Subtropical Hot-Humid Area

by Zhixin Liu, Senlin Zheng and Lihua Zhao

Atmosphere 2018, 9(5), 198; https://doi.org/10.3390/atmos9050198 - 21 May 2018

Cited by 65 | Viewed by 9238

Abstract

Urban trees can significantly improve the outdoor thermal environment, especially in subtropical zones. However, due to the lack of fundamental evaluations of numerical simulation models, design and modification strategies for optimizing the thermal environment in subtropical hot-humid climate zones cannot be proposed accurately. [...] Read more.

Urban trees can significantly improve the outdoor thermal environment, especially in subtropical zones. However, due to the lack of fundamental evaluations of numerical simulation models, design and modification strategies for optimizing the thermal environment in subtropical hot-humid climate zones cannot be proposed accurately. To resolve this issue, this study investigated the physiological parameters (leaf surface temperature and vapor flux) and thermal effects (solar radiation, air temperature, and humidity) of four common tree species (Michelia alba, Mangifera indica, Ficus microcarpa, and Bauhinia blakeana) in both spring and summer in Guangzhou, China. A comprehensive comparison of the observed and modeled data from ENVI-met (v4.2 Science, a three-dimensional microclimate model) was performed. The results show that the most fundamental weakness of ENVI-met is the limitation of input solar radiation, which cannot be input hourly in the current version and may impact the thermal environment in simulation. For the tree model, the discrepancy between modeled and observed microclimate parameters was acceptable. However, for the physiological parameters, ENVI-met tended to overestimate the leaf surface temperature and underestimate the vapor flux, especially at midday in summer. The simplified calculation of the tree model may be one of the main reasons. Furthermore, the thermal effect of trees, meaning the differences between nearby treeless sites and shaded areas, were all underestimated in ENVI-met for each microclimate variable. This study shows that the tree model is suitable in subtropical hot-humid climates, but also needs some improvement. Full article

(This article belongs to the Special Issue Urban Design and City Microclimates)

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16 pages, 57811 KiB

Open AccessArticle

Microclimate Variation and Estimated Heat Stress of Runners in the 2020 Tokyo Olympic Marathon

by Eichi Kosaka, Akiko Iida, Jennifer Vanos, Ariane Middel, Makoto Yokohari and Robert Brown

Atmosphere 2018, 9(5), 192; https://doi.org/10.3390/atmos9050192 - 17 May 2018

Cited by 27 | Viewed by 9689

Abstract

The Tokyo 2020 Olympic Games will be held in July and August. As these are the hottest months in Tokyo, the risk of heat stress to athletes and spectators in outdoor sporting events is a serious concern. This study focuses on the marathon [...] Read more.

The Tokyo 2020 Olympic Games will be held in July and August. As these are the hottest months in Tokyo, the risk of heat stress to athletes and spectators in outdoor sporting events is a serious concern. This study focuses on the marathon races, which are held outside for a prolonged time, and evaluates the potential heat stress of marathon runners using the COMFA (COMfort FormulA) Human Heat Balance (HBB) Model. The study applies a four-step procedure: (a) measure the thermal environment along the marathon course; (b) estimate heat stress on runners by applying COMFA; (c) identify locations where runners may be exposed to extreme heat stress; and (d) discuss measures to mitigate the heat stress on runners. On clear sunny days, the entire course is rated as ‘dangerous’ or ‘extremely dangerous’, and within the latter half of the course, there is a 10-km portion where values continuously exceed the extremely dangerous level. Findings illustrate which stretches have the highest need for mitigation measures, such as starting the race one hour earlier, allowing runners to run in the shade of buildings or making use of urban greenery including expanding the tree canopy. Full article

(This article belongs to the Special Issue Urban Design and City Microclimates)

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16 pages, 9367 KiB

Open AccessArticle

Microclimate Metrics Linked to the Use and Perception of Public Spaces: The Case of Chillán City, Chile

by Pamela Smith and Cristián Henríquez

Atmosphere 2018, 9(5), 186; https://doi.org/10.3390/atmos9050186 - 14 May 2018

Cited by 5 | Viewed by 4288

Abstract

This paper presents research carried out in the city of Chillán, a medium size city located on the southern limit of the Chilean Mediterranean domain, at 36°36′s south latitude. Chillán provides a good representative example of warm summers in central and southern Chilean [...] Read more.

This paper presents research carried out in the city of Chillán, a medium size city located on the southern limit of the Chilean Mediterranean domain, at 36°36′s south latitude. Chillán provides a good representative example of warm summers in central and southern Chilean cities. Five public spaces were selected, representing different typologies and relating to different urban background conditions. Users in these public spaces were observed, counted and photographed five times a day (12, 14, 16, 18 and 20 h, local time) during a heat wave event in the summer of 2016, while meteorological parameters were measured at different points within the public space. The variables evaluated were impervious surfaces, sky view factor, H/W, azimuth, shadow, and radiation. Local public environmental management should pay attention to the complex relations between urban climate, public spaces and thermal comfort since they affect the quality of life of the most vulnerable sectors of the population. This is particularly important given the increasing episodes of elevated temperatures and intense heat waves which have occurred in the city of Chillán in recent summers, which are related to urban heat islands and climate change. Full article

(This article belongs to the Special Issue Urban Design and City Microclimates)

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18 pages, 4898 KiB

Open AccessEditor’s ChoiceArticle

Analysis and Comparison of Shading Strategies to Increase Human Thermal Comfort in Urban Areas

by Ivan Lee, James A. Voogt and Terry J. Gillespie

Atmosphere 2018, 9(3), 91; https://doi.org/10.3390/atmos9030091 - 01 Mar 2018

Cited by 53 | Viewed by 7005

Abstract

With the expected increase in warmer conditions caused by climate change, heat-related illnesses are becoming a more pressing issue. One way that humans can protect themselves from this is to seek shade. The design of urban spaces can provide individuals with a variety [...] Read more.

With the expected increase in warmer conditions caused by climate change, heat-related illnesses are becoming a more pressing issue. One way that humans can protect themselves from this is to seek shade. The design of urban spaces can provide individuals with a variety of ways to obtain this shade. The objective of this study was to perform a detailed evaluation and comparison of three shading strategies that could be used in an urban environment: shade from a building, from a tree, and from an umbrella. This was done through using field measurements to calculate the impact of each strategy on a thermal comfort index (Comfort Formula (COMFA)) in two urban settings during sunny days of the summer of 2013 and 2014 in London, Canada. Building shade was found to be the most effective cooling strategy, followed by the tree strategy and the umbrella strategy. As expected, the main determinant of this ranking was a strategy’s ability to block incoming shortwave radiation. Further analysis indicated that changes in the convective loss of energy and in longwave radiation absorption had a smaller impact that caused variations in the strategy effectiveness between settings. This suggests that under non-sunny days, these rankings could change. Full article

(This article belongs to the Special Issue Urban Design and City Microclimates)

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28 pages, 7921 KiB

Open AccessArticle

The Impact of Tipuana tipu Species on Local Human Thermal Comfort Thresholds in Different Urban Canyon Cases in Mediterranean Climates: Lisbon, Portugal

by Andre Santos Nouri, Dominik Fröhlich, Maria Matos Silva and Andreas Matzarakis

Atmosphere 2018, 9(1), 12; https://doi.org/10.3390/atmos9010012 - 07 Jan 2018

Cited by 26 | Viewed by 5539

Abstract

Based upon the case of Lisbon, this article examined the in-situ effects of vegetation upon pedestrian thermal comfort levels. Focussing specifically upon the historic quarter that often witnesses the highest T_amb values and Urban Heat Island (UHI) intensities during the summer, the [...] Read more.

Based upon the case of Lisbon, this article examined the in-situ effects of vegetation upon pedestrian thermal comfort levels. Focussing specifically upon the historic quarter that often witnesses the highest T_amb values and Urban Heat Island (UHI) intensities during the summer, the most common urban canyon cases (UCCs) were modelled, along with one of the most commonly used vegetative semi-deciduous species found in the city, Tipuana tipu. Based upon a reference point (RP) system, the assessments were undertaken through the use of a new version of the SkyHelios model, local obtained G_rad values, and the modified physiologically equivalent temperature (mPET) index calculated through the human-biometeorological model RayMan. The study identified the in-situ thermo-physiological influences of Tipuana tipu during different periods of the year: (1) during the summer, which revealed considerable reductions of PET/mPET of up to 15.6 °C/11.6 °C during a very hot day (where daily maximum T_amb surpassed 35 °C); and (2) during the winter, which revealed the risks of oversharing as a result of the species keeping its foliage during the winter with reductions of PET/mPET of up to 2.7 °C/2.6 °C. Furthermore, the study utilised the climate tourism/transfer information scheme (CTIS) to categorise and facilitate the interpretation of the results. Full article

(This article belongs to the Special Issue Urban Design and City Microclimates)

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