The Dependence of Mean Climate State on Shortwave Absorption by Water Vapor

Abstract State-of-the-art climate models exhibit significant spread in the climatological value of atmospheric shortwave absorption (SWA). This study investigates both possible causes and climatic impacts this SWA intermodel spread. The global-mean largely originates from difference water vapor absorptivity. Hence, we alter absorptivity Community Earth System Model, version 1, with Atmosphere 4 (CESM1-CAM4). Increasing leads to a reduction precipitation La Niña–like cooling over tropical Pacific. energy budget suggests that is suppressed as way compensate for increased SWA. driven by weakened surface winds, stabilized planetary boundary layer, cooling. Pacific attributed zonal asymmetry evaporative damping efficiency low cloud enhancement eastern basin. Complementary fixed SSTs simulations suggest latter more fundamental it primarily arises processes. Consistent our experiments, CMIP5/6 higher tend produce toward mean state, highlighting role shaping mean-state patterns.