Structure and Behavior of Mesoscale Cloud Clusters Traveling over the Baiu-Frontal Zone

Abstract

A case study was made of long-lasting mesoscale cloud clusters observed by the Geostationary Meteorological Satellite (GMS) from 13 to 15 July 1986, which formed on the continent and traveled over the Baiu-frontal zone. The cloud clusters separated into southern- and northern-cloud groups around 130°E. The southern-cloud group decreased its traveling speed. New cumulonimbus-cloud groups formed 40 to 80km to the west of the pre-existing group in the southern-cloud group. Further, new cumulonimbus clouds appeared about 15km to the west of the pre-existing one in each group. Simultaneous formation of two scales of convective clouds occurred in the slow-moving cloud group.
The area of traveling clouds, which originated from deep convective clouds in the northern cloud group, lasted for more than 10 hours after the deep convection decayed. Bright bands and streaks were recognized in their radar echo around 135°E. They were located in the layer of convective instability at middle to upper levels, with a large gradient of temperature at 850mb and a synoptic-scale updraft at the middle level around 140°E. It is suggested that the cloud area originating from “convective clouds” was changed to “stratiform clouds.”