Study of the life cycle of tropical cloud and precipitation systems using MTSAT-1R and TRMM data

Observations from the Multi-functional Transport Satellite (MTSAT)-1R and the Tropical Rainfall Measuring Mission (TRMM) satellite are analyzed to show the statistical view of the cloud life cycle, including the changes of vertical structure of rainfall, over the Maritime Continent and a part of the tropical western Pacific. The analysis focuses on the isolated cold cloud systems, which can be considered as fundamental self-organized cloud systems. After identifying temporally connected isolated cold cloud systems by a cloud tracking procedure, spatiotemporally synchronized TRMM observations with the cloud systems were searched and various statistics were computed. Clear life cycle changes of the average reflectivity profile from the Precipitation Radar (PR), such as those of radar echo height and the bright band feature, are statistically confirmed over the ocean area. The long-lived systems in this analysis show a behavior similar to those of typical mesoscale convective systems. The systems start from the intermediate phase between initial and mature stages, reach the mature stage with the maximal cloud and precipitation areas at the mid-period of the lifetime, and decay. The increase of precipitating area is mostly attributed to that of stratiform precipitation. The rain rate and the radar echo height indicate their peak during the early hours and decrease with elapsed time. Precipitation-size ice particles and the higher ratio of lightningaccompanied systems are observed during the early elapsed time, and their peaks seem to synchronize with the peak of the convective-conditional average rain rate. In contrast, shortlived systems in this analysis decay rapidly and do not produce an extension of cloud and precipitation. It is speculated that the systems are already in the mature stage when they are identified, from the observations of higher ratio of stratiform rainfall area and clearer feature of bright band than those of long-lived systems at the time of system formation. The results also show that the difference between rainfall estimates of the TRMM Microwave Imager (TMI) and PR depends on the phase in the lifetime. TMI tends to provide higher conditional average rain rates at mature phase than that of PR. Also, the cold cloud area with an IR brightness temperature threshold of 235 K, which is the basis of the GOES Precipitation Index, does not track the life cycle changes of total rain volume, probably because it mainly reflects the areas of stratiform precipitation and anvil clouds, particularly in the middle and later stages of the long-lived systems. To understand the life cycle of latent heating profiles and its effect on the surrounding atmospheric field, similar statistical analysis is performed for the latent heating profiles derived from the PR rainfall profiles over the isolated cold cloud systems. Clear life cycle variations are confirmed for convective heating profiles, while those in stratiform heating profiles are negligible. The resulting total heating profiles show the heating at all levels during the lifetime and the peak shifts from 5 to 8 km with elapsed time. Because the stratiform rainfall area and its life cycle variations are large, the total heating contribution released by a cold cloud system to the surrounding atmosphere is dominated by changes in the rainfall area and the ratio of the stratiform rainfall, rather than by changes in the shape of convective heating profiles.