HR: 1340h
AN: GC33A-1250    [Abstracts]
TI: Rainstorms Falling on the Sierra Nevada Snowpack: Comparing Radar Observations with Surface Measurements to Better Understand Flood Potential
AU: * Lundquist, J D
EM: Jessica.Lundquist@noaa.gov
AF: NOAA-CIRES Climate Diagnostics Center, 325 Broadway, R/CDC1, Boulder, CO 80305-3328 United States
AU: Ralph, F M
EM: Marty.Ralph@noaa.gov
AF: NOAA Environmental Technology Laboratory, 325 Broadway, R/ETL, Boulder, CO 80305-3328 United States
AU: Neiman, P J
EM: Paul.J.Neiman@noaa.gov
AF: NOAA Environmental Technology Laboratory, 325 Broadway, R/ETL, Boulder, CO 80305-3328 United States
AU: Kingsmill, D E
EM: David.Kingsmill@colorado.edu
AF: NOAA-CIRES Environmental Technology Laboratory, 325 Broadway, R/ETL, Boulder, CO 80305-3328 United States
AU: White, A B
EM: Allen.B.White@noaa.gov
AF: NOAA-CIRES Environmental Technology Laboratory, 325 Broadway, R/ETL, Boulder, CO 80305-3328 United States
AU: Gottas, D J
EM: Daniel.Gottas@noaa.gov
AF: NOAA-CIRES Environmental Technology Laboratory, 325 Broadway, R/ETL, Boulder, CO 80305-3328 United States
AB: Heavy rain falling on dense snowpacks has caused some of the most dramatic floods of the past century, and coastal basins spanning a wide range of elevations, such as the American River Basin in California, are extremely sensitive to these events. Many studies of climatic change show that these same river basins are extremely sensitive to regional warming, which yields a greater percentage of precipitation falling in the form of rain rather than snow, thus increasing the frequencies of floods. In the maritime mountain ranges of North America, most precipitation falls during the winter months, with a large percentage falling in the form of snow. Particularly warm storms result in floods primarily because rain falls at higher elevations and over a much larger contributing area than during a typical storm. Because of the different sizes and fall speeds of rain and snow, Doppler radars are able to detect the melting level in the atmosphere, and automated algorithms are available to make this information available to river forecasters. However, how well do these free-atmosphere observations compare with what happens at the surface? Do hourly radar melting levels, which are beneath the altitude of the 0°C isotherm, correspond better with surface observations than temperature profiles from twice-daily operational soundings? Can coastal radar observations provide early information for storms approaching the Sierra Nevada from the Pacific Ocean? Do patterns of rising and falling melting levels provide key information for flood forecasts? This study compares surface temperature, precipitation, and snowfall data from 10 California Department of Water Resources snow pillow stations at elevations ranging from 1610-2190 m in the Amercan River Basin west of Sacramento with observations from 3 wind profiling radars located roughly west (upstream) of the watershed. These observations are augmented by observations of river discharge and by temperature data from the Oakland radiosonde. Case studies from winter 2005 storms are presented along with statistical correlations between the various datasets.
UR: http://tenaya.ucsd.edu/~jessica/
DE: 0736 Snow (1827, 1863)
DE: 1631 Land/atmosphere interactions (1218, 1843, 3322)
DE: 1821 Floods
DE: 1840 Hydrometeorology
DE: 1895 Instruments and techniques: monitoring
SC: Global Climate Change [GC]
MN: Fall Meeting 2005