The Preliminary Study On Meteorological Mechanism Of Landslip And Debris Flow In Qinling And Bashan Mountainous Regions

In Qinling and Bashan mountainous regions, mountain torrent, landslip and debris flow are the most severe natural disasters, especially the disaster caused by torrential rainstorm, which can induce great personal casualty and property loss for local people and society development. The main reasons for the disaster in Qinling and Bashan mountainous regions are topographical features, geological condition, precipitation and human factors, that can interact under some environment and rain conditions and produce the disaster when the stable state is destroyed or exceed some criticality.In this study, using ordinary meteorological observation data, hydrologic data and geological disaster data, the cause of formation of the disaster in Qinling and Bashan mountainous regions is analyses. Using the new generation mesoscale model of the Weather Research and Forecast (WRF-V2.1) model, the mesoscale numerical simulation of heavy storm rainfall which induced severe mountain disaster is carried out. From the different angle of dynamic and thermodynamic structures, this paper mainly discuss the mesoscale systems, such as low-level jet stream and the low vortex, and draw some useful conclusion by exploring the development feature and physical mechanism of this process.The main conclusions can be summarized as following:The high-level jet at 200hPa, subtropical high at 500hPa and low-level jet at 850hPa are the weather backgrounds favorable to strong precipitation in Qinling and Bashan mountainous regions . The formation and enhancement of mesoscale eddy is very important for the torrential rainstorm in this region, where it lies the right behind side of upper air jet entrance region , the left front side of lower level jet entrance region and the strong ascending movement region with convergence at the low level and divergence at the upper-level. The convergence of cold air from northwestern and warm-wet flow from lower level jet associated with mesoscale lower level jet which can accelerate and enhance the mesoscale low vortex system. The trigger conditions of rainstorm are dynamical lifting of topography and lover-level jet disturbance. The vertical updraft motion can be enhanced because of lower level warm-wet air. Coupling development of updraft motion, vapour conditions and potential instability induce more strongger convection development, which can produce severe rainstorm.