First, the rainfall characteristics of TCs are compared with those of the equatorial (10°N-10°S) mean. The most notable finding here is that the average stratiform rain ratio (SRR), which is the contribution from stratiform rain in the total rainfall, of TCs is 54%, which is larger than that for the equatorial oceanic mean of 44%. Stronger rain is observed in TCs both for convective and stratiform rain. Secondly, analyses of radial rain characteristics of TCs suggest that the region 060 km can be classified as the inner core', and 60500 km as the rainband'. In the inner core, small SRR, very high rain top height, and the large flash rate are observed, indicating the vigor of convective activity. In contrast, in the rainband, large SRR and relatively large rain-yield per flash are observed, which means that it rains efficiently although convective activity is moderate. These results imply that TCs are the most effective kind of rain systems in terms of sustaining vigorous convection thus resulting in large amounts of stratiform rain.
Finally, rainfall contribution of TCs within 500 km radius to the total annual rainfall in the entire TRMM observational region (35°N-35°S) are estimated. Composite rainfall amounts of TCs and the mean lifetime of each stage and TC numbers in each class are utilized for the calculation. As a result, the contribution of 500km-TC rainfall in the entire TRMM observation region is estimated as about 3.2%±0.2%. Contributions of TCs to the total rainfall amount in different basins are also compared.