Moisture budget analysis of extreme precipitation associated with different types of atmospheric rivers over western North America

2021 ◽  
Author(s):  
Yaheng Tan ◽  
Song Yang ◽  
Francis Zwiers ◽  
Ziqian Wang ◽  
Qiaohong Sun
Keyword(s):  
North America ◽  
Extreme Precipitation ◽  
Moisture Budget ◽  
Western North America ◽  
Atmospheric Rivers ◽  
Budget Analysis ◽  
Different Types ◽  
Moisture Budget Analysis

Changes in mechanisms and intensity of Western U.S. floods, 1960-2013

2021 ◽  
Author(s):  
Jessica Fayne ◽  
Huilin Huang ◽  
Mike Fischella ◽  
Yufei Liu ◽  
Zhaoxin Ban ◽  
...  
Keyword(s):  
Extreme Precipitation ◽  
Large Scale ◽  
Critical Factor ◽  
Flood Frequency ◽  
Atmospheric Rivers ◽  
Convective Storms ◽  
Noticeable Increase ◽  
Complex Interactions ◽  
Different Types ◽  
The Impact

<p>Extreme precipitation, a critical factor in flooding, has selectively increased with warmer temperatures in the Western U.S. Despite this, the streamflow measurements have captured no noticeable increase in large-scale flood frequency or intensity. As flood studies have mostly focused on specific flood events in particular areas, analyses of large-scale floods and their changes have been scarce. For floods during 1960-2013, we identify six flood generating mechanisms (FGMs) that are prominent across the Western U.S., including atmospheric rivers and non-atmospheric rivers, monsoons, convective storms, radiation-driven snowmelt, and rain-on-snow, in order to identify to what extent different types of floods are changing based on the dominant FGM. The inconsistency between extreme precipitation and lack of flood increase suggests that the impact of climate change on flood risk has been modulated by hydro-meteorological and physiographic processes such as sharp increases in temperature that drive increased evapotranspiration and decreased soil moisture. Our results emphasize the importance of FGMs in understanding the complex interactions of flooding and climatic changes and explain the broad spatiotemporal changes that have occurred across the vast Western U.S. for the past 50 years.</p>

The Inland Penetration of Atmospheric Rivers over Western North America: A Lagrangian Analysis

2015 ◽  
Vol 143 (5) ◽  
pp. 1924-1944 ◽  
Author(s):  
Jonathan J. Rutz ◽  
W. James Steenburgh ◽  
F. Martin Ralph
Keyword(s):  
Water Vapor ◽  
North America ◽  
Pacific Coast ◽  
Water Vapor Transport ◽  
Western North America ◽  
Lagrangian Analysis ◽  
Initial Water ◽  
Atmospheric Rivers ◽  
The Pacific ◽  
Synoptic Conditions

Abstract Although atmospheric rivers (ARs) typically weaken following landfall, those that penetrate inland can contribute to heavy precipitation and high-impact weather within the interior of western North America. In this paper, the authors examine the evolution of ARs over western North America using trajectories released at 950 and 700 hPa within cool-season ARs along the Pacific coast. These trajectories are classified as coastal decaying, inland penetrating, or interior penetrating based on whether they remain within an AR upon reaching selected transects over western North America. Interior-penetrating AR trajectories most frequently make landfall along the Oregon coast, but the greatest fraction of landfalling AR trajectories that eventually penetrate into the interior within an AR is found along the Baja Peninsula. In contrast, interior-penetrating AR trajectories rarely traverse the southern “high” Sierra. At landfall, interior-penetrating AR trajectories are associated with a more amplified flow pattern, more southwesterly (vs westerly) flow along the Pacific coast, and larger water vapor transport (qυ). The larger initial qυ of interior-penetrating AR trajectories is due primarily to larger initial water vapor q and wind speed υ for those initiated at 950 and 700 hPa, respectively. Inland- and interior-penetrating AR trajectories maintain large qυ over the interior partially due to increases in υ that offset decreases in q, particularly in the vicinity of topographical barriers. Therefore, synoptic conditions and trajectory pathways favoring larger initial qυ at the coast, limited water vapor depletion by orographic precipitation, and increases in υ over the interior are keys to differentiating interior-penetrating from coastal-decaying ARs.

scholarly journals The Role of Circulation and Its Changes in Present and Future Atmospheric Rivers over Western North America

2020 ◽  
Vol 33 (4) ◽  
pp. 1261-1281 ◽  
Author(s):  
Yaheng Tan ◽  
Francis Zwiers ◽  
Song Yang ◽  
Chao Li ◽  
Kaiqiang Deng
Keyword(s):  
Water Vapor ◽  
North America ◽  
Coupled Model ◽  
Teleconnection Pattern ◽  
Water Vapor Transport ◽  
Historical Period ◽  
Western North America ◽  
Atmospheric Rivers ◽  
The North ◽  
Type Frequency

AbstractPerformance in simulating atmospheric rivers (ARs) over western North America based on AR frequency and landfall latitude is evaluated for 10 models from phase 5 of the Coupled Model Intercomparison Project among which the CanESM2 model performs well. ARs are classified into southern, northern, and middle types using self-organizing maps in the ERA-Interim reanalysis and CanESM2. The southern type is associated with the development and eastward movement of anomalous lower pressure over the subtropical eastern Pacific, while the northern type is linked with the eastward movement of anomalous cyclonic circulation stimulated by warm sea surface temperatures over the subtropical western Pacific. The middle type is connected with the negative phase of North Pacific Oscillation–west Pacific teleconnection pattern. CanESM2 is further used to investigate projected AR changes at the end of the twenty-first century under the representative concentration pathway 8.5 scenario. AR definitions usually reference fixed integrated water vapor or integrated water vapor transport thresholds. AR changes under such definitions reflect both thermodynamic and dynamic influences. We therefore also use a modified AR definition that isolates change from dynamic influences only. The total AR frequency doubles compared to the historical period, with the middle AR type contributing the largest increases along the coasts of Vancouver Island and California. Atmospheric circulation (dynamic) changes decrease northern AR type frequency while increasing middle AR type frequency, indicating that future changes of circulation patterns modify the direct effect of warming on AR frequency, which would increase ARs (relative to fixed thresholds) almost everywhere along the North American coastline.

scholarly journals Assessing the climate-scale variability of atmospheric rivers affecting western North America

2017 ◽  
Vol 44 (15) ◽  
pp. 7900-7908 ◽  
Author(s):  
Alexander Gershunov ◽  
Tamara Shulgina ◽  
F. Martin Ralph ◽  
David A. Lavers ◽  
Jonathan J. Rutz
Keyword(s):  
North America ◽  
Western North America ◽  
Atmospheric Rivers ◽  
Climate Scale
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