Mountains Modulate the Response of Precipitation Flashiness to Warming in High‐Resolution Simulations Over the Western US

Abstract

Global climate models (GCMs) robustly predict that precipitation will become flashier (i.e., more concentrated in time) as the climate warms, with extremely wet events accounting for a larger share of total precipitation at a given location. Here we test this prediction across the western United States, where precipitation is modulated by orographic mechanisms that GCMs do not resolve. Using the daily Gini index, we analyze the change in precipitation flashiness within an ensemble of high‐resolution regional climate model (RCM) simulations. In contrast to GCMs, which predict a widespread increase in flashiness, the RCMs indicate decreased flashiness in rain‐shadowed basins downwind of major mountain ranges. We show that this result follows from a weakening of orographic influence on precipitation as the climate warms. A widely used statistical downscaling method fails to capture this effect, and thus misses important features of the flashiness response simulated by RCMs.