Abstract: As the world’s fifth-largest economy and the largest producer of food in the United States, California’s vulnerability to water resource fluctuations is an issue of national and international concern. Recent research focuses on answering questions about the warming climate and its impacts on precipitation variability and snowpack accumulation (as significant water supply) in California. Located in a Mediterranean climate with complex terrain and varied climate divisions, Calfornia’s regional climate is of more concern (or similar regions) with better-informing climate adaptation/mitigation strategies.

In the first part of the talk, an overview of the regional climate modeling will be given, and cutting-edge modeling methods will be introduced, including traditional dynamical downscaling models and variable-resolution options.

With a well-developed modeling framework, a case study will be discussed in the second part of the talk, focusing on the most extreme wet year (2016-2017) in California’s historical record since 1895, which occurred after an extraordinary long-term drought. Results will show how the historical and ppredicted future warming reduces the mountainous snowpack and increases early-season runoff during an extreme wet year induced by intense atmospheric rivers (ARs — narrow and filamentary corridors of enhanced water vapor flux).

As the final part of the talk, AR-event-based work will be discussed, showing how precipitation extremes could be much larger than those of 2016-2017, which caused the Oroville Dam collapse and a severe flooding emergency. The thermodynamic increase of atmospheric water vapor will be discussed along with the dynamical water vapor transportation associated with AR-driven storms.