The Features of Mcs during Their Initiation over Tibetan Plateau in Summer

Using the Polar Satellites IR data in 182 days of the summers of 1998~2000 over Tibetan Plateau, 28,685 Mesoscale Convective Systems (MCSs) and some features during their initiation, such as daily frequency, intensity, shape, daily variation and geographic distribution were automatically tracked and extracted by computer. The results show that the daily mean number of MCSs was 163, among which about 76% was only several hundreds Km in size and small percentage(4%) was over 10Km. The shapes of most of them were band, comma and other irregular types and about 30% of them fell into types of circular and ellipse. The mean minimum temperature at the cloud top of them was around –51°C, the number of MCS in the early afternoon was over twice comparing that in the early morning and the number of MCS with TBB≤-54°C was five times; the MCS initiating area were mainly over the southern Plateau of 33°N where two active regions located over Yaluzangbu River basin and the western Sichuan province to Hengduan Mountain, respectively.