Diverging hydrological sensitivity among tropical basins

The three tropical basins each have unique roles in the global climate system. The main mechanism by which tropical oceans affect remote climate is the latent heating of local precipitation. Here we report major differences in hydrological sensitivity (precipitation change per unit surface warming) among tropical basins. Specifically, the Pacific hydrological sensitivity is several times as large as that of the Indian basin, while the Atlantic hydrological sensitivity is negative. This results from a thermodynamic amplification of the existing spatial unevenness in relative humidity, with the wettest basin getting wetter and the driest basin getting drier. The diverging basin hydrological sensitivity is accompanied by an interbasin repartitioning of latent heating and convective mass fluxes, with far-reaching implications on rainfall and surface temperature over tropical and mid-latitude lands. These results indicate that the previously unrecognized interbasin differences in hydrological sensitivity may contribute substantially to the geographic pattern of anthropogenic climate change.