The relationship between precipitation in the tropics and tropical cyclone frequency

Despite many advances in our knowledge of tropical cyclones, the problem of genesis is still not well understood. In addition to being an interesting scientific problem, the destructive potential of tropical cyclones gives a heightened importance to better understanding genesis. A previous modeling study indicated a close relationship between tropical cyclone frequency and tropical rainfall. This study examines this relationship in observations. The frequency of tropical cyclone genesis is compared to TRMM satellite-based rainfall estimates over specified regions in each ocean basin, on both monthly and seasonal time scales. It is found that there is a statistically significant correlation of r~0.4 between the monthly regionally averaged rainfall anomaly from the mean annual cycle and the monthly tropical cyclone frequency anomaly from the mean annual cycle in each ocean basin. This result is consistent between the ocean basins, while results from similar analysis on seasonal time scales and on monthly time scales without the annual cycle removed vary from region to region.