Climate Change Analysis on Historical Precipitation over Mountainous Watersheds by Means of Dynamical Downscaling of Long-Term Reanalysis

Climate change analysis on historical precipitation was conducted over two study watersheds in Northern California: the Upper Feather River watershed and the Yuba River watershed. It is difficult to obtain sufficient observed precipitation data for a long-term period over such mountainous watersheds. In this study, therefore, historical precipitation was reconstructed for 141 water years from October 1, 1871 thought September 30, 2012 by means of dynamical downscaling of a long-term reanalysis, 20CRv2. After validation with observation data, the reconstructed precipitation was utilized for climate change analysis. The climate change analysis shows that annual basin-average precipitation has significantly increased over the study watersheds during the historical period. An upward trend of monthly basin-average precipitation is significant in drier month whereas it is insignificant in wet months except for February.