Correlation between Sea Surface Temperature and the Frequency of Deep Convection in the Tropical Oceans

The analysis seven years of AIRS and AMSRe data shows that in about 0.5% of the data very strong convection creates Deep Convective Clouds (DCC) which reach the tropopause and are associated with intense precipitation. The warmer the SST the higher the fraction of these DCC. The closer the cloud tops are to the tropopause, the higher the rain rate. The frequency of DCC increases about 50% for each degree K increase in the zonal mean SST. This sensitivity is consistent with a simple model, which assumes that DCC have a high likelihood of forming in the tail of the zonal SST distribution where the local SST exceeds 302 K. Tropical zones, like the tropical warm pool, have more locations with SST>302K, and consequently have a higher frequency of DCC. This simple model appears to be valid for a wide range of SST. The correlation between the zonal mean SST and the DCC frequency allows us to estimate that the frequency of these DCC, and whence the frequency of intense thunderstorms in the tropical oceans, will increase due to global warming by 5%/decade.