The dependence of mean climate state on shortwave absorption by water vapor

The precipitation reduction is driven by the weakened surface winds, stabilized planetary boundary layer, and surface cooling. The La Nina-like cooling over the tropical Pacific is attributed to the zonal asymmetry of climatological evaporative damping efficiency and the low cloud enhancement over the eastern basin. Complementary fixed SSTs simulations suggest that the latter is more fundamental and that it primarily arises from atmospheric processes.

Consistent with our experiments, the CMIP5/6 models with a higher global-mean SWA tend to produce tropical Pacific toward a more La Nina-like mean state, highlighting the possible role of water vapor shortwave absorptivity for shaping the mean-state climate patterns.