scholarly journals Constraining and Characterizing the size of Atmospheric Rivers: A perspective independent from the detection algorithm.

2021 ◽  
Author(s):  
Héctor Alejandro Inda Díaz ◽  
Travis Allen O'Brien ◽  
Yang Zhou ◽  
William D. Collins
Keyword(s):  
Detection Algorithm ◽  
Atmospheric Rivers

scholarly journals The Influence of Atmospheric Rivers over the South Atlantic on Winter Rainfall in South Africa

2018 ◽  
Vol 19 (1) ◽  
pp. 127-142 ◽  
Author(s):  
R. C. Blamey ◽  
A. M. Ramos ◽  
R. M. Trigo ◽  
R. Tomé ◽  
C. J. C. Reason
Keyword(s):  
South Africa ◽  
South African ◽  
Extreme Rainfall ◽  
Detection Algorithm ◽  
Winter Rainfall ◽  
Atmospheric Rivers ◽  
The North ◽  
Study Support ◽  
Topographic Barriers ◽  
High Topography

Abstract A climatology of atmospheric rivers (ARs) impinging on the west coast of South Africa (29°–34.5°S) during the austral winter months (April–September) was developed for the period 1979–2014 using an automated detection algorithm and two reanalysis products as input. The two products show relatively good agreement, with 10–15 persistent ARs (lasting 18 h or longer) occurring on average per winter and nearly two-thirds of these systems occurring poleward of 35°S. The relationship between persistent AR activity and winter rainfall is demonstrated using South African Weather Service rainfall data. Most stations positioned in areas of high topography contained the highest percentage of rainfall contributed by persistent ARs, whereas stations downwind, to the east of the major topographic barriers, had the lowest contributions. Extreme rainfall days in the region are also ranked by their magnitude and spatial extent. The results suggest that although persistent ARs are important contributors to heavy rainfall events, they are not necessarily a prerequisite. It is found that around 70% of the top 50 daily winter rainfall extremes in South Africa were in some way linked to ARs (both persistent and nonpersistent). Overall, the findings of this study support similar investigations on ARs in the North Atlantic and North Pacific.

A Climatology of Atmospheric Rivers and Associated Precipitation for the Seven U.S. National Climate Assessment Regions

2020 ◽  
Vol 21 (11) ◽  
pp. 2439-2456
Author(s):  
Emily A. Slinskey ◽  
Paul C. Loikith ◽  
Duane E. Waliser ◽  
Bin Guan ◽  
Andrew Martin
Keyword(s):  
Great Plains ◽  
Moisture Transport ◽  
Regional Scale ◽  
Detection Algorithm ◽  
Water Vapor Transport ◽  
The West ◽  
Regional Patterns ◽  
Atmospheric Rivers ◽  
Climate Assessment ◽  
National Climate Assessment

AbstractAtmospheric rivers (ARs) are long, narrow filamentary regions of enhanced vertically integrated water vapor transport (IVT) that play an important role in regional water supply and hydrometeorological extremes. Here, an AR detection algorithm is applied to global reanalysis from Modern-Era Retrospective Analysis for Research and Applications, version 2 (MERRA-2), to objectively and consistently characterize ARs regionally across the continental United States (CONUS). The characteristics of AR and associated precipitation are computed at the gridpoint scale and summarized over the seven U.S. National Climate Assessment regions. ARs are most frequent in the autumn and winter in the West, spring in the Great Plains, and autumn in the Midwest and Northeast. ARs show regional and seasonal variability in basic geometry and IVT. AR IVT composites reveal annually consistent northeastward-directed moisture transport from the Pacific Ocean in the West, whereas moisture transport patterns vary seasonally across the Southern Great Plains and Midwest. Linked AR precipitation characteristics suggest that a substantial proportion of extreme events, defined as the top 5% of 3-day precipitation totals, are associated with ARs over many parts of CONUS, including the East. Regional patterns of AR-associated precipitation highlight that seasonally varying moisture transport and lifting mechanisms differ between the East and the West where orographic lifting is key. Our study aims to contribute a comprehensive and consistent CONUS-wide, regional-scale analysis of ARs in support of ongoing NCA efforts. Given the CONUS-wide role ARs play in extreme precipitation, findings motivate continued study of associated climate change impacts.

scholarly journals The impact of atmospheric rivers on rainfall in New Zealand

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Jingxiang Shu ◽  
Asaad Y. Shamseldin ◽  
Evan Weller
Keyword(s):  
New Zealand ◽  
Austral Summer ◽  
Daily Rainfall ◽  
Extreme Rainfall ◽  
Detection Algorithm ◽  
Extreme Rainfall Events ◽  
Rainfall Events ◽  
Atmospheric Rivers ◽  
Hydrological Hazards ◽  
The Impact

AbstractThis study quantifies the impact of atmospheric rivers (ARs) on rainfall in New Zealand. Using an automated AR detection algorithm, daily rainfall records from 654 rain gauges, and various atmospheric reanalysis datasets, we investigate the climatology of ARs, the characteristics of landfalling ARs, the contribution of ARs to annual and seasonal rainfall totals, and extreme rainfall events between 1979 and 2018 across the country. Results indicate that these filamentary synoptic features play an essential role in regional water resources and are responsible for many extreme rainfall events on the western side of mountainous areas and northern New Zealand. In these regions, depending on the season, 40–86% of the rainfall totals and 50–98% of extreme rainfall events are shown to be associated with ARs, with the largest contributions predominantly occurring during the austral summer. Furthermore, the median daily rainfall associated with ARs is 2–3 times than that associated with other storms. The results of this study extend the knowledge on the critical roles of ARs on hydrology and highlight the need for further investigation on the landfalling AR physical processes in relation to global circulation features and AR sources, and hydrological hazards caused by ARs in New Zealand.

scholarly journals Impacts of Atmospheric Rivers on Precipitation in Southern South America

2018 ◽  
Vol 19 (10) ◽  
pp. 1671-1687 ◽  
Author(s):  
Maximiliano Viale ◽  
Raúl Valenzuela ◽  
René D. Garreaud ◽  
F. Martin Ralph
Keyword(s):  
South America ◽  
West Coast ◽  
Detection Algorithm ◽  
Water Vapor Transport ◽  
The South ◽  
Southern South America ◽  
Atmospheric Rivers ◽  
The Andes ◽  
Hourly Data ◽  
The Impact

Abstract This study quantifies the impact of atmospheric rivers (ARs) on precipitation in southern South America. An AR detection algorithm was developed based on integrated water vapor transport (IVT) from 6-hourly CFSR reanalysis data over a 16-yr period (2001–16). AR landfalls were linked to precipitation using a comprehensive observing network that spanned large variations in terrain along and across the Andes from 27° to 55°S, including some sites with hourly data. Along the Pacific (west) coast, AR landfalls are most frequent between 38° and 50°S, averaging 35–40 days yr−1. This decreases rapidly to the south and north of this maximum, as well as to the east of the Andes. Landfalling ARs are more frequent in winter/spring (summer/fall) to the north (south) of ~43°S. ARs contribute 45%–60% of the annual precipitation in subtropical Chile (37°–32°S) and 40%–55% along the midlatitude west coast (37°–47°S). These values significantly exceed those in western North America, likely due to the Andes being taller. In subtropical and midlatitude regions, roughly half of all events with top-quartile precipitation rates occur under AR conditions. Median daily and hourly precipitation in ARs is 2–3 times that of other storms. The results of this study extend knowledge of the key roles of ARs on precipitation, weather, and climate in the South American region. They enable comparisons with other areas globally, provide context for specific events, and support local nowcasting and forecasting.

scholarly journals Constraining and Characterizing the size of Atmospheric Rivers: A perspective independent from the detection algorithm.

2020 ◽  
Author(s):  
Héctor Alejandro Inda Díaz ◽  
Travis Allen O'Brien ◽  
Yang Zhou ◽  
William D. Collins
Keyword(s):  
Detection Algorithm ◽  
Atmospheric Rivers

scholarly journals An Intercomparison between Reanalysis and Dropsonde Observations of the Total Water Vapor Transport in Individual Atmospheric Rivers

2018 ◽  
Vol 19 (2) ◽  
pp. 321-337 ◽  
Author(s):  
Bin Guan ◽  
Duane E. Waliser ◽  
F. Martin Ralph
Keyword(s):  
Water Vapor ◽  
Detection Algorithm ◽  
Vapor Transport ◽  
Water Vapor Transport ◽  
Dual Purpose ◽  
Representative Sampling ◽  
Atmospheric Rivers ◽  
Geographical Variations ◽  
Northeastern Pacific ◽  
Selection Of

Abstract A recent study presented nearly two decades of airborne atmospheric river (AR) observations and concluded that, on average, an individual AR transports ~5 × 108 kg s−1 of water vapor. The study here compares those cases to ARs independently identified in reanalyses based on a refined algorithm that can detect less well-structured ARs, with the dual-purpose of validating reanalysis ARs against observations and evaluating dropsonde representativeness relative to reanalyses. The first comparison is based on 21 dropsonde-observed ARs in the northeastern Pacific and those closely matched, but not required to be exactly collocated, in ERA-Interim (MERRA-2), which indicates a mean error of −2% (−8%) in AR width and +3% (−1%) in total integrated water vapor transport (TIVT) and supports the effectiveness of the AR detection algorithm applied to the reanalyses. The second comparison is between the 21 dropsonde ARs and ~6000 ARs detected in ERA-Interim (MERRA-2) over the same domain, which indicates a mean difference of 5% (20%) in AR width and 5% (14%) in TIVT and suggests the limited number of dropsonde observations is a highly (reasonably) representative sampling of ARs in the northeastern Pacific. Sensitivities of the comparison to seasonal and geographical variations in AR width/TIVT are also examined. The results provide a case where dedicated observational efforts in specific regions corroborate with global reanalyses in better characterizing the geometry and strength of ARs regionally and globally. The results also illustrate that the reanalysis depiction of ARs can help inform the selection of locations for future observational and modeling efforts.

Daily Precipitation Extreme Events in the Iberian Peninsula and Its Association with Atmospheric Rivers*

2015 ◽  
Vol 16 (2) ◽  
pp. 579-597 ◽  
Author(s):  
Alexandre M. Ramos ◽  
Ricardo M. Trigo ◽  
Margarida L. R. Liberato ◽  
Ricardo Tomé
Keyword(s):  
Iberian Peninsula ◽  
Extreme Precipitation ◽  
North Atlantic Ocean ◽  
Detection Algorithm ◽  
Ocean Basin ◽  
Ranking List ◽  
Atmospheric Rivers ◽  
The North ◽  
The Impact

Abstract An automated atmospheric rivers (ARs) detection algorithm is used for the North Atlantic Ocean basin that allows the identification and a comprehensive characterization of the major AR events that affected the Iberian Peninsula over the 1948–2012 period. The extreme precipitation days in the Iberian Peninsula and their association (or not) with the occurrence of ARs is analyzed in detail. The extreme precipitation days are ranked by their magnitude and are obtained after considering 1) the area affected and 2) the precipitation intensity. Different rankings are presented for the entire Iberian Peninsula, for Portugal, and for the six largest Iberian river basins (Minho, Duero, Tagus, Guadiana, Guadalquivir, and Ebro) covering the 1950–2008 period. Results show that the association between ARs and extreme precipitation days in the western domains (Portugal, Minho, Tagus, and Duero) is noteworthy, while for the eastern and southern basins (Ebro, Guadiana, and Guadalquivir) the impact of ARs is reduced. In addition, the contribution from ARs toward the extreme precipitation ranking list is not homogenous, playing an overwhelming role for the most extreme precipitation days but decreasing significantly with the less extreme precipitation days. Moreover, and given the narrow nature of the ARs, the location of the ARs over each subdomain is closely related to the occurrence (or not) of extreme precipitation days.

scholarly journals Aerosol Atmospheric Rivers: Climatology, Event Characteristics, and Detection Algorithm Sensitivities

2022 ◽  
Author(s):  
Sudip Chakraborty ◽  
Bin Guan ◽  
Duane Waliser ◽  
Arlindo da Silva
Keyword(s):  
Detection Algorithm ◽  
Width Ratio ◽  
Boreal Winter ◽  
Mixing Ratio ◽  
Aerosol Transport ◽  
Atmospheric Rivers ◽  
Planetary Scale ◽  
Aerosol Mass ◽  
Aerosol Emission ◽  
Length Width

Abstract. Leveraging the concept of atmospheric rivers (ARs), a detection technique based on a widely utilized global algorithm to detect ARs (Guan et al., 2018; Guan and Waliser, 2015, 2019) was recently developed to detect aerosol atmospheric rivers (AARs) using the Modern-Era Retrospective analysis for Research and Applications, Version 2 reanalysis (Chakraborty et al., 2021a). The current study further characterizes and quantifies various details of AARs that were not provided in that study, such as AARs’ seasonality, event characteristics, vertical profiles of aerosol mass mixing ratio and wind speed, and the fraction of total annual aerosol transport conducted by AARs. Analysis is also performed to quantify the sensitivity of AAR detection to the criteria and thresholds used by the algorithm. AARs occur more frequently over, and typically extend from, regions with higher aerosol emission. For a number of planetary-scale pathways that exhibit large climatological aerosol transport, AARs contribute 40–80 % to the total annual transport. DU AARs are more frequent in boreal spring, SS AARs are often more frequent during the boreal winter (summer) in the Northern (Southern) Hemisphere, CA AARs are more frequent during dry seasons and often originate from the global rainforests and industrial areas, and SU AARs are present in the Northern Hemisphere during all seasons. For most aerosol types, the mass mixing ratio within AARs is highest near the surface and decreases monotonically with altitude. However, DU and CA AARs over or near the African continent exhibit peaks in their aerosol mixing ratio profiles around 700 hPa. AAR event characteristics are mostly independent of species with mean length, width, and length/width ratio around 4000 km, 600 km, and 8, respectively.

scholarly journals All-Season Climatology and Variability of Atmospheric River Frequencies over the North Pacific

2016 ◽  
Vol 29 (13) ◽  
pp. 4885-4903 ◽  
Author(s):  
Bryan D. Mundhenk ◽  
Elizabeth A. Barnes ◽  
Eric D. Maloney
Keyword(s):  
North Pacific ◽  
Seasonal Cycle ◽  
Southern Oscillation ◽  
Detection Algorithm ◽  
Cold Season ◽  
Water Vapor Transport ◽  
Reanalysis Dataset ◽  
Atmospheric Rivers ◽  
The North ◽  
The North Pacific

Abstract Recent work on atmospheric rivers (ARs) has led to a characterization of these impactful features as primarily cold-season phenomena. Here, an all-season analysis of AR incidence in the North Pacific basin is performed for the period spanning 1979–2014 using the NASA Modern-Era Retrospective Analysis for Research and Applications (MERRA) reanalysis dataset. An occurrence-based detection algorithm is developed and employed to identify and characterize ARs in instantaneous fields of anomalous vertically integrated water vapor transport. The all-season climatology and variability of AR frequencies due to the seasonal cycle, the El Niño–Southern Oscillation (ENSO), the Madden–Julian oscillation (MJO), and their interactions are presented based on composites of the detected features. The results highlight that ARs exist throughout the year over the North Pacific, although their preferred locations shift substantially throughout the year. This seasonal cycle manifests itself as northward and westward displacement of ARs during the Northern Hemisphere warm seasons, rather than an absolute change in the number of ARs within the domain. It is also shown that changes to the North Pacific mean-state due to ENSO and the MJO may enhance or completely offset the seasonal cycle of AR activity, but that such influences on AR frequencies vary greatly based on location.

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