The Role of Clouds in Shaping Tropical Pacific Response Pattern to
Extratropical Thermal Forcing
Abstract
Extratropical influences on tropical sea surface temperature (SST) have
implications for decadal predictability. We implement a cloud-locking
technique to highlight the critical role of clouds in shaping tropical
SST response to extratropical thermal forcing. With heating imposed over
either extratropical Northern Atlantic or Pacific, Hadley Cells respond
similarly that the trades strengthen south of the rainband. The
wind-evaporation-SST (WES) feedback leads to cooling over the southern
subtropics, which is enhanced in the southeastern Pacific due to the
positive feedback between SST and stratiform clouds. This cooling is
further extended toward the central Pacific via a WES effect associated
with zonally contrasting cloud-radiative-SST feedbacks in the tropics,
which is observed in both slab-ocean and dynamical-ocean experiments. We
propose that the meridional and zonal SST gradients are tightly linked
via WES effects and the cloud-radiative-SST feedbacks, which are largely
determined by the climatological rainband position and the spatial
distribution of cloud properties.