Explaining darker deep convective clouds over the western Pacific than over tropical continental convective regions

[摘要] This study attempted to explain why deep convective clouds (DCCs) over thewestern Pacific are generally darker than those found over tropical Africanand South American land regions. The western Pacific domain was furtherdivided into its land and ocean regions to deduce the general differences inDCC characteristics between convectively active tropical land and oceanregions. DCC in this study is defined as a single-layer cloud whosethickness is greater than 15 km, and it is determined from CloudSat-measuredreflectivity profiles. Corresponding MODIS-measured reflectivities at 0.645 μmwere examined, along with the analysis of cloud products from CloudAerosol Lidar Infrared Pathfinder Satellite Observation (CALIPSO)measurements.

From an analysis of the four January months of 2007–2010, a distinctdifference in ice water path (IWP) between the ocean region of the westernPacific and the three tropical land regions was revealed. Distinctdifferences in the effective radius between land and ocean were also found.The findings lead to a conclusion that smaller IWP over the western Pacificocean region than over the tropical land regions, which should be caused bydifferent cloud microphysics between land and ocean, is the main cause ofsmaller reflectivity there.

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