Relative Importance of the Annual Cycles of Sea Surface Temperature and Solar Irradiance for Tropical Circulation and Precipitation: A Climate Model Simulation Study

Abstract A recent version of the Goddard Earth Observing System GCM which contains several upgrades to the model's prognostic cloud physics and microphysics as well as snow and ice hydrology, was used to isolate the influences of the annual cycles of solar irradiation and sea surface temperatures (SSTs) on the annual cycle of circulation and precipitation. Four 50-month-long integrations were produced with the GCM. The first integration, called the control simulation, C, was forced with daily interpolated SSTs from a 30-yr climatology of monthly SST data. In this simulation both SSTs and incoming solar irradiance had their normally prescribed annual cycles. The next two companion simulations were called S1, which used annual mean prescribed incoming solar irradiation, and S2, which used annual mean prescribed SST; everything else was kept similar to C in these two simulations. In the fourth simulation, called S3, both SSTs and incoming solar irradiation at the top of the atmosphere were prescribed to alwa...