How warming impacts precipitation extremes and snowpack over complex regions like California?

Abstract: As the world’s fifth-largest economy and largest producer of food in the U.S., California’s vulnerability to water resource fluctuations is an issue of national and international concern. Recent research focuses on answering the questions about warming climate and its impacts on the precipitation variability and snowpack accumulation (as a significant water supply) over California. Locating in a Mediterranean climate with complex terrain and varied climate divisions, regional climate is more of concern over California (or regions alike) with better informing climate adaptation/mitigation strategies. In the first part of the talk, 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-development modeling framework, a case study will be discussed in the second part of the talk, focusing on the most extreme wet year (i.e. 2016-2017) of the historical record since 1895 over California, after an extraordinary long-term drought. Results will show how the historical and prescribed future warming reduces the mountainous snowpack and increase early-season runoff, under such extreme wet year induced by intense atmospheric rivers (i.e. ARs, defining as narrow and filamentary corridors of enhanced water vapor flux). As the third and last part of the talk, ARs event-based work will be discussed, showing how the precipitation extremes could be much larger than the one of year 2016-2017, which already 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 extratropical cyclones.