HR: 1340h
AN: U53A-0718    [Abstracts]
TI: Trends in Snowfall Versus Rainfall for the Western United States
AU: * Knowles, N
EM: nknowles@usgs.gov
AF: USGS, 345 Middlefield Rd., MS496, Menlo Park, CA 94025 United States
AU: Dettinger, M D
EM: mdettinger@ucsd.edu
AF: Scripps Institution of Oceanography, 9500 Gilman Dr., La Jolla, CA 92093-0224 United States
AU: Cayan, D R
AF: Scripps Institution of Oceanography, 9500 Gilman Dr., La Jolla, CA 92093-0224 United States
AB: The western U.S. depends heavily on snowpack to help retain its wintertime freshwater endowment into the drier spring and summer months. A well-documented shift towards earlier runoff can be attributed to 1) more precipitation falling as rain instead of snow, and 2) earlier snowmelt. The present study shows a regional trend toward a decreasing ratio of winter snow water equivalent (SWE) to total precipitation since 1948. This trend is attributable to a shift toward more rainfall rather than a decrease in overall precipitation. At the monthly scale, the trend is most pronounced in January (coastally) and March (west-wide), corresponding to warming trends in those months for average wet-day maximum temperatures. Implications for historical and projected runoff timing shifts are discussed.
DE: 1655 Water cycles (1836)
DE: 1833 Hydroclimatology
DE: 1860 Runoff and streamflow
DE: 1863 Snow and ice (1827)
SC: Union [U]
MN: 2004 AGU Fall Meeting