Historical Climate Change Analysis over American River Watershed by Means of 137-Year Long-Term Dynamic Downscaling

Thursday, 18 December 2014
Kei Ishida1, ML Levent Kavvas1, ZhiQiang Richard Chen2, Noriaki Ohara3 and Suhyung Jang4, (1)University of California Davis, Davis, CA, United States, (2)California Department of Water Resources, Sacramento, CA, United States, (3)University of Wyoming, Laramie, WY, United States, (4)Korea Water Resources Corporation, Korea Institute of Water and Environment, Daejeon, South Korea
Historical precipitation over Northern California during 137 water years from October, 1872 to September, 2008 is reconstructed by means of a physically-based regional atmospheric model. NOAA Twentieth Century Reanalysis version 2 (20CR) is utilized as the initial and boundary conditions. The reconstructed precipitation is validated by comparing with Parameter-elevation Regressions on Independent Slopes Model (PRISM) monthly precipitation over the American River watershed (ARW) in Northern California. The correlation coefficient and the Nash–Sutcliffe coefficient were 0.925 and 0.793, respectively. Then, the basin-average precipitation over ARW is analyzed. The analysis shows that the annual basin-average precipitation increased during the reconstructed period. The mean monthly precipitation of the late period (wy1872-1940) is higher for every month than that of the early period (wy1940-2008). Moreover, frequency analyses of 6-, 12-, 24-, 48-, 72-, and 96-hour accumulated basin-average precipitation were conducted. The results show that the peak value of basin-average precipitation also increased.