UCLA

This study investigates how radiation and other forcing factors, such as temperature, precipitation, and snow water equivalent (SWE) influence snowmelt runoff in 20 river basins in the Western United States. The forcing values are derived from gridded observations of precipitation and temperature, and other surface variables (such as downward solar and longwave radiation, and humidity). Using daily runoff from U.S. Geological Survey streamflow records, this paper calculated several indexes to describe the timing and magnitude of snowmelt induced spring runoff peaks and rising limb of the hydrograph. Pearson correlation coefficients is used to analyze the relationships between forcings and runoff indexes. The results show that snowmelt runoff tends to be earlier and lower at higher temperature. With higher precipitation or SWE, snowmelt runoff tends to be later and larger. For most sites, with higher net radiation, snowmelt runoff tends to be earlier. But only for some of the sites, with higher net radiation, snowmelt runoff tends to be smaller. For other sites, the magnitude of snowmelt runoff is not correlated with net radiation.