Tropical Cyclone Activity under Varying SSTs in Aquaplanet Simulations

A high (50-km) resolution aquaplanet version of the GFDL Atmosphere Model 4.0 is forced by zonally symmetric sea surface temperature (SST) and used to investigate tropical cyclone (TC) activity. A parameter sweep is performed to investigate the sensitivity of TC genesis frequency, lifetime, and average intensity to the prescribed SST distribution. TC numbers show a non-monotonic dependence on the latitude of the SST maximum, increasing as the SST maximum moves northward off the equator and then falling again. Notably, a substantial number of high-energy, long-lived TCs are evident even when the SST maximum is shifted well into the mid-latitudes. The total accumulated cyclone energy, a function of the number of TCs, their lifetime, and their intensity, follows the TC frequency in exhibiting non-monotonic behavior as the SST maximum is moved poleward. Results suggest that future changes in TC activity will be modulated by changes in the large-scale circulation.