For the 2011 Northeast Tropical Conference
Tropical circulation driven by a weak SST gradient
Zhiming Kuang
Department of Earth and Planetary Sciences and School of Engineering and Applied Sciences, Harvard University
Abstract
As a starting point to understanding steady tropical circulations, we consider the Walker circulation driven by a small amplitude sinusoidal sea surface temperature (SST) perturbation. A set of cloud-system-resolving simulations of various planetary scale domain sizes (tens of thousands of kilometers) shows that for the same amplitude SST perturbation, the resulting circulation is considerably stronger and more bottom-heavy for the longer domain sizes. Surface pressure, intriguingly, is higher over the warmest water. Limited domain model simulations with parameterized feedbacks from the large-scale flow are used to interpret the results. At planetary scales, temperature anomalies required to drive the circulation can significantly affect convection. As a result, details of convective momentum transport, which affect the temperature anomalies required to drive the circulation, become an integral part of how the circulation responses to the SST forcing.
Zhiming Kuang <kuang@fas.harvard.edu>