Satellite-Observed Characteristics of Winter Monsoon Cloud Clusters

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  • 1 Department of Atmospheric Sciences, University of Washington, Seattle, WA 98195
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Abstract

An objective algorithm is devised which is capable of touting tropical cloud clusters at the point of initiation, tracking them to the paint of dissipation and thereby accumulating statistics on their size distributions and preferred geographical locations and times of occurrence. The technique is able to account for periods of growth, mergers, splits and decay, which take place during the lifetime of an individual cluster. It is used to derive statistics on cloud clusters observed during the Winter Monsoon Experiment, which was conducted in the region of the “maritime continent,” near Borneo, in December, 1978. The size distribution of the clusters identified and tracked shows that by far most of the cumulative cloud cover was accounted for by a few very large clusters. This result implies that the vertical distribution of diabatic heating in the region of the experiment was strongly influenced by dynamical and radiative processes in the widespread stratiform cloud and precipitation areas that typify very large clusters. A pronounced diurnal cycle was characterized by a preference for the very large clusters to reach the middle of their lifetime over the sea during morning. Monsoon “surge” conditions over the South China Sea also strongly favored the occurrence of large clusters over the water north of Borneo.

Abstract

An objective algorithm is devised which is capable of touting tropical cloud clusters at the point of initiation, tracking them to the paint of dissipation and thereby accumulating statistics on their size distributions and preferred geographical locations and times of occurrence. The technique is able to account for periods of growth, mergers, splits and decay, which take place during the lifetime of an individual cluster. It is used to derive statistics on cloud clusters observed during the Winter Monsoon Experiment, which was conducted in the region of the “maritime continent,” near Borneo, in December, 1978. The size distribution of the clusters identified and tracked shows that by far most of the cumulative cloud cover was accounted for by a few very large clusters. This result implies that the vertical distribution of diabatic heating in the region of the experiment was strongly influenced by dynamical and radiative processes in the widespread stratiform cloud and precipitation areas that typify very large clusters. A pronounced diurnal cycle was characterized by a preference for the very large clusters to reach the middle of their lifetime over the sea during morning. Monsoon “surge” conditions over the South China Sea also strongly favored the occurrence of large clusters over the water north of Borneo.

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