The Influence of SST Forcing on Simulated Precipitation and Drought

Previous studies suggest that ocean-atmosphere forcing by slowly varying sea surface temperature (SST) anomalies is a primary driver of seasonal-to-interannual hydroclimatic variability, including drought. In this study, we evaluate the influence of ocean-atmosphere forcing on precipitation and drought characteristics by comparing two ensembles of AGCM simulations forced with observed (interannually varying) monthly SST and their climatological annual cycle, respectively. Our results suggest that the influence of SST on the interannual variance of seasonal precipitation is significant throughout the tropics and many mid- and high latitude regions. However, SST anomalies do not significantly influence the autocorrelation of seasonal precipitation anomalies or the frequency, duration, and magnitude of drought events outside of the tropics-- i.e., while SST anomalies influence the likelihood of drought during a given season, ocean-atmosphere forcing does not significantly influence aggregate drought characteristics. These results bear important implications for seasonal-to-interannual precipitation prediction in general, and long-range drought prediction in particular.