Analysis and Numerical Simulation of a Severe Heavy Rainfall in Shandong Peninsula

A diagnosis and simulation study have been conducted to reveal the feature of the heavy rainstorm in the east of Shandong Peninsula on 5 August 2004 by using T213 data and routine observation data.The evolutionary process and development mechanism of the heavy rainstorm process are analyzed with emphasis on the orogrphic effect of Shandong Peninsula on the development of the upper and low-level jets as well as the development of vortex in the boundary layer.The simulated results indicated that the moving echo of radar from south to north along with the rainstorm showed the structure and development of the mesocal systems.The low-level jet(LLJ) and upper-level jet(ULJ) intensified with the development of convective system while they reached the Shandong Peninsula.The center of LLJ which lay to the south of the mesocal systems was caused by the southwest ward warm air current on the western side of the western Pacific ocean subtropical high.The upper-level mesoscal jet formed by the upper level outflow of convection occurred during the evolution of convection.The interaction of LLJ and mesoscale ULJ could maintain and accelerate the development of convective system.It is also shown that the meso-β-scale vortex was produced in the boundary on the western side of the western Pacific ocean subtropical high.After its formation,this meso-β-scale vortex moved northwest ward accompanied with heavy rainstorm and the moving route of this meso-β-scale vortex is related to the distribution of the topography in Shandong Peninsula.The southwest warm air current was blocked by Shandong Peninsula and forced to move around it,which was one of the reasons the heavy rainstorm occurring in Weihai,Shandong Province.