Cloud systems over the Maritime Continent and the tropical western Pacific defined by the Geostationary Meteorological Satellite (GMS) were tracked, and their evolution was compared with cloud parameters [e.g., minimum blackbody brightness temperature (TBB), cloud area size, TBB gradient at cloud edges]. In addition, cloud systems observed by the Tropical Rainfall Measuring Mission (TRMM) were examined, and the relationship with precipitation was investigated. Analysis areas were divided into four regions: open ocean, coastal sea, coasts, and land.Cloud systems that did not split from or merge with other systems (28% of a total of 290 717 cloud systems) showed common features on cloud parameters in spite of different lifetimes or their locations. While the minimum TBB appeared in the beginning of their lifetimes, the cloud area was still expanding. At the time of first detection, the TBB gradient at the edge of the cloud system was the maximum and decreased with time. The rain rate was maximized when the TBB was at a minimum or earlier. For example, a system with the lifetime of 5 h over the ocean has a minimum TBB 2 h after the occurrence, a maximum area at 3 h, a maximum TBB gradient at 1 h, and a maximum rain rate at 1 h. Vertical development was significant in coasts, while remarkable horizontal expansion appeared over land. In particular, precipitation ice and storm height profiles showed differences among regions.
Tropical Rainfall Measuring Mission observations from multiple sensors including precipitation radar, microwave and infrared radiometers, and a lightning sensor were used to describe precipitation, lightning frequency, and microphysical properties of precipitating clouds over the midlatitude ocean. Precipitation over midlatitude oceans was intense during winter and was often accompanied by frequent lightning. Case studies over the western North Pacific from January and February 2000 showed that some lightning occurred in deep precipitating clouds that developed around cyclones and their attendant fronts. Lightning also occurred in convective clouds that developed in regions of large-scale subsidence behind extratropical cyclones where cold polar air masses were strongly heated and moistened from below by the ocean. The relationships between lightning frequency and the minimum polarization corrected temperature (PCT) at 37 and 85 GHz and the profile of the maximum radar reflectivity resembled relationships derived previously for cases in the Tropics. Smaller lapse rates in the maximum radar reflectivity above the melting level indicate vigorous convection that, although shallow and relatively rare, was as strong as convection over tropical oceans. Lightning was most frequent in systems for which the minimum PCT at 37 GHz was less than 260 K. Lightning and PCT at 85 GHz were not as well correlated as lightning and PCT at 37 GHz. Thus, lightning was frequent in convective clouds that contained many large hydrometeors in the mixed-phase layer, because PCT is more sensitive to large hydrometeors at 37 than at 85 GHz. The relationship between lightning occurrence and cloud-top heights derived from infrared observations was not straightforward. Microphysical conditions that support lightning over the midlatitude ocean in winter were similar to conditions in the Tropics and are consistent with Takahashi’s theory of riming electrification.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.