# Studies of General Precipitation Features with TRMM PR Data: An Extensive Overview
## 6 Conclusions and Prospects
### Summary of Precipitation Studies of PR Data
The application studies of PR data could obtain many convincing relationships between variations of geographical, rainfall types, diurnal and climatological variables and the precipitation features, as generalized in this article from the existing studies, adding greatly to our understanding of rainfall processes in tropical regions that would not have been possible without PR. Some general precipitation features yielded from majority studies are listed as follows:  
(1) Lightning was more likely to occur over land for convective rainfall than over oceans for stratiform rainfall, and more likely to be accompanied by intense rainfall. The related vertical structure of rainfall tended to be uniform with the absence of the bright band. (2) The latent heat profiles of rainfall tended to have two slightly stronger peaks in the early morning over oceans while having one much stronger peak in the late afternoon over land. (3) The precipitation height tended to be higher for convective rainfall over land than stratiform rainfall over oceans and there was a positive relationship between the precipitation height and the rainfall intensity. The vertical profiles of precipitation tended to have a larger negative slope at low altitudes but a small slope at high altitudes for convective rainfall over land than stratiform rainfall over oceans. (4) The diurnal variation of rainfall tended to have peaks with larger amplitudes at afternoon over land while with smaller amplitudes at early morning over oceans. Over land, the peaks in the afternoon for convective precipitation were stronger and hours earlier than stratiform precipitation, and the stratiform precipitation could have other peaks in the evening. (5) The monsoon onsets were accompanied by simultaneously increased stratiform and convective precipitation. The contribution of stratiform precipitation and convective precipitation to the rainfall amount had comparable differences for different monsoon regions. (6) The stratiform precipitation played an important role in tropical cyclones with a larger proportion of areal coverage than the convective precipitation, while the two types of precipitation contributed almost equally to the rainfall amount. These findings and the differences of precipitation features between rainfall types and underlying surfaces may identify crucial roles of water vapor content, vertical velocity and long-wave radiation in tropical rainfall processes. The water vapor abundance over land was less than that over oceans and the vertical velocity of convective rainfall was larger than stratiform rainfall so that the extension altitudes were higher for convective rainfall over land than stratiform rainfall over oceans. The thermal inertia of underlying surfaces and the longwave radiative cooling of clouds regulated the amplitude and the phase of diurnal cycles and made them larger and earlier over land than over oceans. Meanwhile, the smaller thermal inertia of land made atmosphere stratification instability more apparent over land and thus the stratiform rainfall had a remarkably larger proportion and areal coverage over oceans and over the global than the convective rainfall. Consequently, the convection activities were more frequent over land than over oceans while the rainfall systems over oceans like tropical cyclones were constituted largely by stratiform precipitation than convective precipitation. However, we are aware of the limitations in this review due to the manner in which we searched literature (e.g., missing studies), and biases due to the classification of studies. In addition, due to the differences between the used methods and the products and the lack of detailed interpretation for quantitative analysis in the various studies, we did not derive higher accurate estimates or pooled distribution diagrams of precipitation features by analyzing the error or utilizing the weighted average from the individual studies.