The Weather Classification And Typical Process Analysis For Rainstorms Inducing Floods In Northeast China

Northeast China, with lots of rivers passing through, is an important industrial and agricultural base but generally suffers from shortage of water resources. Moreover, it is struck by flood disasters from time to time, due to the climatic conditions that the regional rainfall is more of the summer type or the summer-autumn type, and the varied weather systems causing rainstorms lead to an uneven temporal and spatial distribution. When it comes to how to avoid flood disasters to the hilt and make effective advantage of storm-water resources,the key premise is to forecast the rainstorms inducing floods first,of which the foundation is the classification of rainstorms weather.Here are the main contents of this paper and what have obtained about the weather classification and typical process analysis for rainstorms inducing floods in Northeast China:(1)Based on the precipitation data of Hunjiang River Basin from 1971 to 2010 and the surface weather maps of East Asia from 1991 to 2010,the weather types and paths of rainstorms inducing floods in Northeast China are summed up, in which process avoid the problems including unclear division of high layer and surface factors, sketchy surface type etc.There are mainly six weather types of rainstorms inducing floods in Northeast China, including Mongolian cyclone, the Yellow River cyclone,Jiang Huai(Huang Huai) cyclone, tropical cyclone, Northeast cyclone and inverted trough of low pressure. Most of them belong to rolling-in low pressures. Five of them almost have the same influencing frequency except for tropical cyclones. However, the principal weather types that give rise to rainstorms and the level above are inverse inverted trough and the Yellow river cyclone. But every time a tropical cyclone comes up, despite its less frequency of occurrence and brings about heavier rainfalls.(2)A typical rainstorm process in the Biliuhe River Basin on April 24 th,2012 was diagnostically analyzed in the aspects of circulation and physical quantities fields by using the“Objective Analysis and Graphic Software”,in order to find the features of its genesis,development and termination. It is also expected to verify the classification of rainstorm weather types and provide useful methods of forecasting that kind of rainstorms inducing floods. As a typical case,the rainstorm process in the Biliuhe River basin on April 24 th,2012is a combined action of a north-moving Jiang Huai cyclone affecting Northeast China that takes the sea-entering track, and the front of a mass of south-moving cold air. As the main body of the cold air prevailed, the rainfall gradually ceased. Coming from the Southwest and South China, the vapor arrives over the Biliuhe River Basin and comes across the instability of atmosphere, which helps to reinforce the rainstorm. Though the rainstorm doesn’t coincide with the prime of either the cold air or the cyclone, the special geographical situation adds up by ttie favorable conditions of vapor and dynamics, contributed to the rainstorm precipitating just on the above-mentioned river basin. In terms of this rainstorm process,the wet potential vorticity plays a more dominant role of indicating about the rainfall area and period. Besides,the rainstorm intensity could have been greatly strengthened provided the convergence and ascending motion had been concurrent with the strongest vapor transport.