Study On Space-time Distributing Features Of Mesoscale Convective System In Xinjiang

Xinjiang is surrounded by high mountains. With the Tianshan Mountains span through the central area, it is divided into two wide open basins, one in the south, and the other in the north. Although it is far away from oceans and has arid climate, there are frequent occurrences of disastrous weather such as hailstones, local heavy storms, and sandstorms. This study is undertaken in order to get a comprehensive understanding of the Meso-scale Convective System (MCS hereafter) in Xinjiang. This thesis consists of six chapters. The main conclusions include:(1) By studying the Japanese geosynchronous weather satellite GMS-5 hourly infrared cloud data from 1998 to 2000, there were totally 160 occurrences of MCS in Xinjiang. The spatial distribution of those MCS was analyzed. The result shows that the MCS primarily occur in two regions. One is the windward of Tianshan Mountains, east to Yili river valley and exactly where the days of annual precipitation occurs in Xinjiang. The other is the surrounding area of Keping, leeward of western Tianshan Mountains where has the most frequent occurrences of sandstorms, In addition, there are another two secondly regions. One is the Yanqi basin where the Bositeng Lake is located in. The other is in the north of Kunlun Mountains, west to Taklimakan Desert. There is barely occurrence of MCS in Guerbantonggute Desert, north of Xinjiang, whereas fairly in the south of Taklimakan Desert, and frequently in the west as well as the north of Taklimakan Desert.(2) Analysis on annual cycle of Xinjiang MCS shows that: MCS occur mostly in later spring and throughout the summer, and rarely in autumn and winter. It peaks in June, with 24% of MCS happening in this month, much more than the other months, followed by July and May, totaling16% and 7% respectively, and least in February and March. For Taklimakan Desert, it peaks in May.(3) Statistical analysis on Xinjiang MCS life span was conducted. The result shows that: a majority of MCS are formed in the afternoon to the evening (14:00 -19:00AM), a part of them in the evening (20:00 -24:00PM), and even a small part of them in the early...