Analysis Of Climate Characteristic Of Rainstorm In Guizhou Province

Based on the conventional climate statistics analysis, Empirical Orthogonal Function and related analysis, daily precipitation data of the 75 observation stations of GuiZhou Province offered by GuiZhou Province Climate Center are used to study the spatial-temporal distribution, the characteristics of evolving of torrential rain, and the long period changing tendency of the annual precipitation in recent 48 years. The results indicate that the annual precipitation is between 1100mm and 1300mm, the maximum is up to 1500mm and the minimum is about 840mm. The annual precipitation in the south of GuiZhou is more than that in north. There are 3 centres of the most annual precipitation and 3 the least one. The location of the most annual precipitation canters are the southwest, southeast and northeast of GuiZhou. Among the three centers, the southwest one is the biggest one and the most annual precipitation center of whole province. The location of the least annual precipitation canters are the area along WeiNing, HeZhang and Bijie country, the area along DaoZhen, ZhengAn and TongZhi country at the north of DaLou Mountain, the area along ShiBing and ZhenYuan country at the basin of WuYang River. The area of more rainstorm is identical to the area of more annual precipitation, the annual precipitation of rainstorm is 12～32% of the total annual precipitation, the number of the annual average rainstorm days are 1.6～4.9days. The most rainstorm and downpour happen in summer time. June is the most concentrated time section that the seasonal, monthly and the period of ten-days distribution of rainstorm. Annual precipitation decreases, the precipitation of rainstorm in summer increase, while decreasing in spring and autumn. The precipitation of the east and west of GuiZhou Province is contrary to the precipitation of the middle, the northeast to the southwest and the southeast to the northwest are as the same, when the precipitation of the east and the west increase(decrease), the precipitation of the middle decrease(increase). There is no rainstorm during the last third of December to the first third of February of next year, neither large rainstorm during the middle of November to the middle of March of next year, All of the extraordinary rainstorm are happened during the last third of May to the middle of September except the first and middle third of August.The mechanism of GuiZhou rainstorm is accord with the physical condition of normal rainstorm. The trigger condition and the feedback of the rainstorm itself are conductive to rainstorm; the large scale landform (Tibetan Plateau) is beneficial to GuiZhou rainstorm. The meso-scale system caused by the local landform convergence line, the convergence and the lift-up action of the flared landform influence the rainstorm in GuiZhou obviously. There are 4 major weather systems causing rainstorm in GuiZhou directly that cold front and trough, southern trough, vortex and shear line and typhoon. According to the influence path and the high-and-low profile of the weather systems, the four major systems can be further compartmentalized. The Cold Front and Trough Model contains two types that the cold front southward from north and cold front-genesis configuring upper trough, that is the main weather systems causing heavy-rain in spring, early summer and autumn. The Southern Trough Model includes two type that trough-heat-low-pressure and trough-quasi-stationary-front configuring cold air, that is the main systems causing rainstorm in spring and autumn. The three weather systems that the cold-front and quasi-stationary-front shear line, eastward or southeastward moving southwest vortex and plateau vortex, upper shear line between the West Pacific Subtropical High and the Qinghai-Xizang High are the main systems causing heavy-rain in summer. And the westward typhoon from GuangDong Province coast is the major system causing rainstorm in summer.