Faculty Sponsor(s)

Jason Cordeira

Abstract

California water resources are heavily dependent on the precipitation associated with atmospheric rivers (ARs). This study is a 20-yr cool season (October–March) climatology that examines the vertical distribution of (IVT) in ARs over the Russian River (RRW) and Santa Ana River Watersheds (SARW). Cool-season precipitation data from PRISM is averaged over the RRW and SARW for the 20-year period 1999–2019. IVT magnitude and direction are calculated using water vapor flux and wind data from NASA MERRA in 50-hPa layers at 38°N 123.125°W for the RRW and 33°N 117.125°W for the SARW. AR events with IVT magnitudes greater than 250 kg m-1s-1(IVT250 events) in the RRW generate up to ~70% of total annual precipitation and generate up to ~60% of total annual precipitation in the SARW. The vertical structure of IVT250 events is analyzed to investigate the distribution of water vapor flux in the lower troposphere (1000-700 hPa), the upper troposphere (700-300-hPa), the direction of IVT relative to terrain, and precipitation totals. IVT concentrated in the 1000-700-hPa layer, and southwesterly ARs explains 73% of the variance of precipitation totals in the RRW and 48% of the variance in the SARW.

Start Date

12-4-2019 1:00 PM

End Date

12-4-2019 2:00 PM

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Dec 4th, 1:00 PM Dec 4th, 2:00 PM

Analysis of Water Vapor Transport and Precipitation Over the Russian River and Santa Ana River Watersheds in California.

California water resources are heavily dependent on the precipitation associated with atmospheric rivers (ARs). This study is a 20-yr cool season (October–March) climatology that examines the vertical distribution of (IVT) in ARs over the Russian River (RRW) and Santa Ana River Watersheds (SARW). Cool-season precipitation data from PRISM is averaged over the RRW and SARW for the 20-year period 1999–2019. IVT magnitude and direction are calculated using water vapor flux and wind data from NASA MERRA in 50-hPa layers at 38°N 123.125°W for the RRW and 33°N 117.125°W for the SARW. AR events with IVT magnitudes greater than 250 kg m-1s-1(IVT250 events) in the RRW generate up to ~70% of total annual precipitation and generate up to ~60% of total annual precipitation in the SARW. The vertical structure of IVT250 events is analyzed to investigate the distribution of water vapor flux in the lower troposphere (1000-700 hPa), the upper troposphere (700-300-hPa), the direction of IVT relative to terrain, and precipitation totals. IVT concentrated in the 1000-700-hPa layer, and southwesterly ARs explains 73% of the variance of precipitation totals in the RRW and 48% of the variance in the SARW.