Research

25 pages, 4228 KiB

Open AccessArticle

The Hydrometeorology Testbed–West Legacy Observing Network: Supporting Research to Applications for Atmospheric Rivers and Beyond

by Andrea J. Ray and Allen B. White

Atmosphere 2019, 10(9), 533; https://doi.org/10.3390/atmos10090533 - 10 Sep 2019

Cited by 2 | Viewed by 3041

Abstract

An observing network has been established along the United States west coast that provides up to 20 years of observations to support early warning, preparedness and studies of atmospheric rivers (ARs). The Hydrometeorology Testbed–West Legacy Observing Network, a suite of upper air and [...] Read more.

An observing network has been established along the United States west coast that provides up to 20 years of observations to support early warning, preparedness and studies of atmospheric rivers (ARs). The Hydrometeorology Testbed–West Legacy Observing Network, a suite of upper air and surface observing instruments, is now an official National Oceanic and Atmospheric Administration (NOAA) observing system with real-time data access provided via publicly available websites. This regional network of wind profiling radars and co-located instruments also provides observations of boundary layer processes such as complex-terrain flows that are not well depicted in the current operational rawindsonde and radar networks, satellites, or in high-resolution models. Furthermore, wind profiling radars have been deployed ephemerally for projects or campaigns in other areas, some with long records of observations. Current research uses of the observing system data are described as well as experimental products and services being transitioned from research to operations and applications. We then explore other ways in which this network and data library provide valuable resources for the community beyond ARs, including evaluation of high-resolution numerical weather prediction models and diagnosis of systematic model errors. Other applications include studies of gap flows and other terrain-influenced processes, snow level, air quality, winds for renewable energy and the predictability of cloudiness for solar energy industry. Full article

(This article belongs to the Special Issue Atmospheric Rivers)

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18 pages, 5273 KiB

Open AccessArticle

Modeling Streamflow Enhanced by Precipitation from Atmospheric River Using the NOAA National Water Model: A Case Study of the Russian River Basin for February 2004

by Heechan Han, Jungho Kim, V. Chandrasekar, Jeongho Choi and Sanghun Lim

Atmosphere 2019, 10(8), 466; https://doi.org/10.3390/atmos10080466 - 14 Aug 2019

Cited by 22 | Viewed by 4001

Abstract

This study aims to address hydrological processes and impacts of an atmospheric river (AR) event that occurred during 15–18 February 2004 in the Russian River basin in California. The National Water Model (NWM), a fully distributed hydrologic model, was used to evaluate the [...] Read more.

This study aims to address hydrological processes and impacts of an atmospheric river (AR) event that occurred during 15–18 February 2004 in the Russian River basin in California. The National Water Model (NWM), a fully distributed hydrologic model, was used to evaluate the hydrological processes including soil moisture flux, overland flow, and streamflow. Observed streamflow and volumetric soil water content data were used to evaluate the performance of the NWM using various error metrics. The simulation results showed that this AR event (15–18 February 2004) with a long duration of precipitation could cause not only deep soil saturation, but also high direct runoff depth. Taken together, the analysis revealed the complex interaction between precipitation and land surface response to the AR event. The results emphasize the significance of a change of water contents in various soil layers and suggest that soil water content monitoring could aid in improving flood forecasting accuracy caused by the extreme events such as the AR. Full article

(This article belongs to the Special Issue Atmospheric Rivers)

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17 pages, 12761 KiB

Open AccessArticle

Asian Long-Range Transport in Relation to Atmospheric Rivers in Northern California

by Catherine N. Liu, Sen Chiao and Ju-Mee Ryoo

Atmosphere 2019, 10(6), 313; https://doi.org/10.3390/atmos10060313 - 05 Jun 2019

Cited by 1 | Viewed by 2753

Abstract

The study investigates the effect of aerosol long-range transport on precipitation over Northern California during atmospheric river (AR) events in the 2017 cold season (January–April). ARs in 2017 were one of the strongest to date, and the intense precipitation associated with the ARs [...] Read more.

The study investigates the effect of aerosol long-range transport on precipitation over Northern California during atmospheric river (AR) events in the 2017 cold season (January–April). ARs in 2017 were one of the strongest to date, and the intense precipitation associated with the ARs resulted in flooding, destruction of property, and contamination of water supplies. The Aerosol Optical Depth (AOD) from Moderate Resolution Imaging Spectroradiometer (MODIS) data shows Asian dust traveling across the Northern Pacific Ocean along with AR events. Aerosol measurements in California, provided by the Interagency Monitoring of Protected Visual Environments (IMPROVE), show that more Asian dust tends to be observed over the coast, while non-Asian/localized dust is observed inland. A mixture of Asian and localized dust is observed over the mountains, although higher amounts of both are observed in the spring (March–April). Back trajectory analysis confirms that Asian aerosols are transported along the air parcels, and each AR event has its own transport pattern in terms of horizontal advection and vertical lifting. Correlation between precipitation and aerosols is low. This suggests that aerosols contribute little to the decrease of local precipitation during the 2017 AR events. Full article

(This article belongs to the Special Issue Atmospheric Rivers)

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16 pages, 13295 KiB

Open AccessArticle

Numerical Investigations of Atmospheric Rivers and the Rain Shadow over the Santa Clara Valley

by Dalton Behringer and Sen Chiao

Atmosphere 2019, 10(3), 114; https://doi.org/10.3390/atmos10030114 - 03 Mar 2019

Cited by 5 | Viewed by 3505

Abstract

This study investigated precipitation distribution patterns in association with atmospheric rivers (ARs). The Weather Research and Forecasting (WRF) model was employed to simulate two strong atmospheric river events. The precipitation forecasts were highly sensitive to cloud microphysics parameterization schemes. Thus, radar observed and [...] Read more.

This study investigated precipitation distribution patterns in association with atmospheric rivers (ARs). The Weather Research and Forecasting (WRF) model was employed to simulate two strong atmospheric river events. The precipitation forecasts were highly sensitive to cloud microphysics parameterization schemes. Thus, radar observed and simulated

Z_{H}

and

Z_{D R}

were evaluated to provide information about the drop-size distribution (DSD). Four microphysics schemes (WSM-5, WSM-6, Thompson, and WDM-6) with nested simulations (3 km, 1 km, and 1/3 km) were conducted. One of the events mostly contained bright-band (BB) rainfall and lasted less than 24 h, while the other contained both BB and non-bright-band (NBB) rainfall, and lasted about 27 h. For each event, there was no clear improvement in the 1/3 km model, over the 1 km model. Overall, the WDM-6 microphysics scheme best represented the rainfall and the DSD. It appears that this scheme performed well, due to its relative simplicity in ice and mixed-phase microphysics, while providing double-moment predictions of warm rain microphysics (i.e., cloud and rain mixing ratio and number concentration). The other schemes tested either provided single-moment predictions of all classes or double-moment predictions of ice and rain (Thompson). Considering the shallow nature of precipitation in atmospheric rivers and the high-frequency of the orographic effect enhancing the warm rain process, these assumptions appear to be applicable over the southern San Francisco Bay Area. Full article

(This article belongs to the Special Issue Atmospheric Rivers)

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13 pages, 1706 KiB

Open AccessArticle

Evaluating the Roles of Rainout and Post-Condensation Processes in a Landfalling Atmospheric River with Stable Isotopes in Precipitation and Water Vapor

by Hari T. Mix, Sean P. Reilly, Andrew Martin and Gavin Cornwell

Atmosphere 2019, 10(2), 86; https://doi.org/10.3390/atmos10020086 - 19 Feb 2019

Cited by 7 | Viewed by 4395

Abstract

Atmospheric rivers (ARs), and frontal systems more broadly, tend to exhibit prominent “V” shapes in time series of stable isotopes in precipitation. Despite the magnitude and widespread nature of these “V” shapes, debate persists as to whether these shifts are driven by changes [...] Read more.

Atmospheric rivers (ARs), and frontal systems more broadly, tend to exhibit prominent “V” shapes in time series of stable isotopes in precipitation. Despite the magnitude and widespread nature of these “V” shapes, debate persists as to whether these shifts are driven by changes in the degree of rainout, which we determine using the Rayleigh distillation of stable isotopes, or by post-condensation processes such as below-cloud evaporation and equilibrium isotope exchange between hydrometeors and surrounding vapor. Here, we present paired precipitation and water vapor isotope time series records from the 5–7 March 2016, AR in Bodega Bay, CA. The stable isotope composition of surface vapor along with independent meteorological constraints such as temperature and relative humidity reveal that rainout and post-condensation processes dominate during different portions of the event. We find that Rayleigh distillation controls during peak AR conditions (with peak rainout of 55%) while post-condensation processes have their greatest effect during periods of decreased precipitation on the margins of the event. These results and analyses inform critical questions regarding the temporal evolution of AR events and the physical processes that control them at local scales. Full article

(This article belongs to the Special Issue Atmospheric Rivers)

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23 pages, 9829 KiB

Open AccessArticle

An Expanded Investigation of Atmospheric Rivers in the Southern Appalachian Mountains and Their Connection to Landslides

by Douglas K. Miller, Chelcy Ford Miniat, Richard M. Wooten and Ana P. Barros

Atmosphere 2019, 10(2), 71; https://doi.org/10.3390/atmos10020071 - 09 Feb 2019

Cited by 16 | Viewed by 5608

Abstract

Previous examination of rain gauge observations over a five-year period at high elevations within a river basin of the southern Appalachian Mountains showed that half of the extreme (upper 2.5%) rainfall events were associated with an atmospheric river (AR). Of these extreme events [...] Read more.

Previous examination of rain gauge observations over a five-year period at high elevations within a river basin of the southern Appalachian Mountains showed that half of the extreme (upper 2.5%) rainfall events were associated with an atmospheric river (AR). Of these extreme events having an AR association, over 73% were linked to a societal hazard at downstream locations in eastern Tennessee and western North Carolina. Our analysis in this study was expanded to investigate AR effects in the southern Appalachian Mountains on two river basins, located 60 km apart, and examine their influence on extreme rainfall, periods of elevated precipitation and landslide events over two time periods, the ‘recent’ and ‘distant’ past. Results showed that slightly more than half of the extreme rainfall events were directly attributable to an AR in both river basins. However, there was disagreement on individual ARs influencing extreme rainfall events in each basin, seemingly a reflection of its proximity to the Blue Ridge Escarpment and the localized terrain lining the river basin boundary. Days having at least one landslide occurring in western North Carolina were found to be correlated with long periods of elevated precipitation, which often also corresponded to the influence of ARs and extreme rainfall events. Full article

(This article belongs to the Special Issue Atmospheric Rivers)

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13 pages, 5733 KiB

Open AccessArticle

Influence of Boreal Winter Intraseasonal Variation of Aleutian Low on Water Vapor Transport and Atmospheric Rivers

by Yating Xiong, Qiuyu Chen and Xuejuan Ren

Atmosphere 2019, 10(2), 49; https://doi.org/10.3390/atmos10020049 - 28 Jan 2019

Cited by 9 | Viewed by 3997

Abstract

The Aleutian Low (AL) operates multiple time scales. The intraseasonal variation of AL is responsible for the subseasonal variability over the pan-North Pacific region. Atmospheric water vapor transport and atmospheric rivers (ARs) changes associated with the intraseasonal variation of AL are investigated over [...] Read more.

The Aleutian Low (AL) operates multiple time scales. The intraseasonal variation of AL is responsible for the subseasonal variability over the pan-North Pacific region. Atmospheric water vapor transport and atmospheric rivers (ARs) changes associated with the intraseasonal variation of AL are investigated over the North Pacific region for the winters of 1979–2014 in this study. The AL’s intraseasonal variation with a peak period of 40 days is identified. A total of 43 events that demonstrate the AL’s feature of strengthening and then weakening is picked and used for composition analysis. During the AL’s strengthening stage, eastward water vapor transport is dominant to the west of 150° W over the mid-basin. Meanwhile, poleward transport is dominant between 150–125° W. During the AL’s weakening stage, the eastward transport is weakened, and the poleward transport is concentrated over the center basin. Accompanied by the AL’s intraseasonal intensity oscillation, the frequency of ARs firstly increases, and then decreases over the ARs’ climatological mean body region over the North Pacific. The moisture source over the western North Pacific is hoarded during non-AR days, while the moisture sinks over the northeastern North Pacific during the AL’s strengthening stage, and the moisture sources over the center basin during the AL’s weakening stage converge during AR days. Hydroclimate effects on anomalies in precipitation over the west coast of North America are also analyzed. Full article

(This article belongs to the Special Issue Atmospheric Rivers)

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15 pages, 3770 KiB

Open AccessArticle

Impacts of Atmospheric Rivers in Extreme Precipitation on the European Macaronesian Islands

by Alexandre M. Ramos, Ricardo M. Trigo, Ricardo Tomé and Margarida L. R. Liberato

Atmosphere 2018, 9(8), 325; https://doi.org/10.3390/atmos9080325 - 20 Aug 2018

Cited by 13 | Viewed by 4419

Abstract

The European Macaronesia Archipelagos (Azores, Madeira and Canary Islands) are struck frequently by extreme precipitation events. Here we present a comprehensive assessment on the relationship between atmospheric rivers and extreme precipitation events in these three Atlantic Archipelagos. The relationship between the daily precipitation [...] Read more.

The European Macaronesia Archipelagos (Azores, Madeira and Canary Islands) are struck frequently by extreme precipitation events. Here we present a comprehensive assessment on the relationship between atmospheric rivers and extreme precipitation events in these three Atlantic Archipelagos. The relationship between the daily precipitation from the various weather stations located in the different Macaronesia islands and the occurrence of atmospheric rivers (obtained from four different reanalyses datasets) are analysed. It is shown that the atmospheric rivers’ influence over extreme precipitation (above the 90th percentile) is higher in the Azores islands when compared to Madeira or Canary Islands. In Azores, for the most extreme precipitation days, the presence of atmospheric rivers is particularly significant (up to 50%), while for Madeira, the importance of the atmospheric rivers is reduced (between 30% and 40%). For the Canary Islands, the occurrence of atmospheric rivers on extreme precipitation is even lower. Full article

(This article belongs to the Special Issue Atmospheric Rivers)

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