Climate Change Effects on Snow-Precipitation Ratio over Northern California in the 21st Century

Abstract:

Snow-precipitation ratio over Northern California during the 21th Century was obtained by means of dynamical downscaling technique and physically-based snow model based on projected future scenarios. Then, climate change effects on the snow-precipitation ratio, and snow accumulation and melt processes were analyzed. The American River watershed (ARW), the Yuba River watershed (YRW), and the Upper Feather River watershed (UFRW) are selected as study watersheds in Northern California. Fifteen future projections based on Intergovernmental Panel on Climate Change (IPCC) Special Report on Emissions Scenarios (SRES) A1, A2, and B1 scenarios projected by General Circulation Models (GCMs) are selected. The dynamical downscaled results, not only precipitation and temperature, but also humidity, wind field, and radiation, were used for inputs to a physically-based snow model. Before future climate simulations, the snow model was validated based on NCEP/NCAR Reanalysis data by comparing its results with snow water equivalent observation data. The simulated results by the snow model show good agreements with snow water equivalent at observation stations over the study watersheds. After the validation, the snow model was applied to the future scenarios. The snow simulation results show that the ratio of snow to precipitation gradually decreases over all over the three watersheds during the 21th century.