Possible Future Changes in Atmospheric Rivers using a Pseudo-Global Warming Approach

Atmospheric rivers are responsible for most of the largest winter flood events in the Western United States. In a warmer climate, the saturated vapor pressure increases and ARs can carry more water vapor. While future global climate model simulations consistently show that the strongest ARs are projected to become more intense and frequent, the effects on precipitation are more difficult to assess due to the small-scale processes that govern orographic precipitation. In this work we use high-resolution simulations with the Weather Research and Forecast (WRF) model to evaluate the possible future changes in precipitation for individual extreme AR events. We use a pseudo-global warming approach to understand how AR-related precipitation can potentially change in a warmer climate due to differences in thermodynamics. The results show that despite generalized increases in IVT, precipitation response is heterogeneous in space. These precipitation changes are used as input to hydrological models for impacts assessment at two watersheds in the Western United States.