The figures show the global rainfall distribution by month over a period of 1998 measured by PR. An El Nino phenomenon, which is warmer sea surface temperature than normal years over the eastern equatorial Pacific, occurred in 1997-98. El Nino is well known to cause changes in atmospheric circulation patterns and abnormal
weather around the world. When an El Nino event occurs, locations of active convecitive areas can be changed. Latent heat is released into the atmosphere during the process that generates rainfall and differences in location and
altitude of latent heat release affect atmospheric circulations.
TRMM has made it possible for the first time to quantitatively measure the three-dimensional distribution of rainfall. Such quantitative information of rainfall
distribution will make it possible to clarify atmospheric convection, which is the driving force of general circulation. Therefore, it is expected to be useful for future understanding of climate, such as El Nino and abnormal weather.
It is clear that heavy rainfall in low latitude are zonally concentrated in the summer hemisphere through the year. In addition to such seasonal changes, heavy rainfall areas, that are normally observed in the western Pacific
shifted to the central Pacific during the winter of 1998, because of the El Nino event. In May, the amount of rainfall in the Asian monsoon region rapidly increased with the onset of the monsoon season. Also El Nino event rapidly
decayed at this time. Rapid changes of the location of the Inter-Tropical Convergence Zone(ITCZ), which is a zonal heavy rainfall area in the tropics. |
