The Numerical Study Of The Rainstorm Occurred In Shandong Province In May2009

Circulation patterns and moisture condition of the rainstorm was analyzed using the NCEP reanalysis data. At1200UTC on May9in2009, high level circulation shows that584dagpm geopotential height line suddenly moves to the northwest development, playing a blocking role on the upstream system. In the mid-level, Qinghai-Tibet Plateau appears as a strong low pressure center. To the east side, there is a narrow low-pressure belt, wind shear occurs in the low pressure zone. In the lower level, there is a shear line and the horizontal through and the formation of the frontal on the ground. Relative humidity is larger than90%in the precipitation region on850hPa. Water vapor transport in south China follows two ways.In Gao qing, there was three significant increase in precipitation. The torrential rain is simulated using the mesoscale model WRF, and high-resolution model output data is used in a diagnostic analysis. We find that the first time of rain increasing occurs mainly in the convergence area made by the discontinuity of wind direction and speed of the south side of the vortex. The conversing of the southerly wind momentum causes the strong upward motion delivered to the high-level. Then there is the strong southerly wind outflow in the north of the convection center. Rainstorm suddenly enhanced when the convergence center moved northward with the low-level positive vorticity. A small southerly wind jet center formed in the middle and lower troposphere to strengthen and the precipitation strengthening.The reason for the change of the vertical relative vorticity was analyzed using the classical vorticity equation. The horizontal advection and deformation effects are the main reasons for the local vorticity change. Vorticity growth is mainly affected by the deformation effect. We analyze the change of the horizontal divergence and find that the development of vorticity is mainly caused by the potential energy and kinetic energy. In addition, the secondary circulation makes low-level convergence and upper level divergence.Making a comparation research of potential temperature, moisture potential temperature, generalized potential temperature, the Richardson number, wet Richardson number and the generalized Richardson number. The results show that the generalized is better to judge the instability in the region of heavy rain.Quality spiral factor, the gradient factor of generalized potential temperature advection, advection of the heat gradient factor and dynamic vorticity vector are used to forcast the position of the rain. The results show that the factors have good ability to predict it.