The Research Of Local Rainstorm Characteristics And Formation Mechanism At Northwestern Of South China Sea Coast

Based on historical meteorological data from 1980 to 2012 and ERA- interim reanalysis data to to study the climatic characteristics of the South China Sea in the northwest coast of local rainstorm and large scale circulation type; To use hourly observation data, radar data and satellite data and FNL reanalysis data for the case of two typical local rainstorm the dynamic condition, moisture condition, thermal analysis, and use WRF model to study three kinds of land surface process scheme for local rainstorm simulation of the effect and the Lei Zhou peninsula of local land the influence of the storm. The main conclusions are as follows:From 1980 to 2012, the northwest coast of the South China Sea local rainstorm have 739 times, the annual average 22.4 times, the local rainstorm occurred from May to August. Winter is almost no local rainstorm occurred. From 1985 to 1992 and from 2002 to 2008 the number of local rainstorm less than normal, while the ones great than normal from 1993 to 2001. South China Sea in the northwest coast of local rainstorm was an increasing trend, but a increasing trend is not significant.From 1980 to 2012, there are total 739 local rainstorm.By analysis the large-scale circulation of 739 local rainstorm at 500 hPa found that the northwest coast of the South China Sea caused local rainstorm have five categories large scale circulation: two ridges of a groove, a ridge two slots, multi-wave, cold vortex-type, low circulation patterns and the other type. Two ridges of a groove in the northwest coast of the South China Sea caused by local rainstorm event a total of 30 times, which significant feature is the west of the Ural Mountains and the Asian region have high pressure at the high latitudes and the Baikal region has a trough or vortex. Two slots of a ridge in the northwest coast of the South China Sea caused by torrential rain event altogether local 107, the significant features of western Siberia and the east coast of Asia trough, Lake Baikal region of the ridge. Multi-wave pattern have total 236 times rainstorm events, which is the most easily to lead to local rainstorm of the South China Sea in the northwest coast, which significant feature is the high-latitude circulation has not less than 3 waves, smaller amplitude in Eurasia within range, high-latitude regions have low pressure center. Northeast cold vortex type have 124 times, which significant feature is the Northeast China has a deep low pressure system, and the Ural mountain region without a deep trough. Low circulation type, a total of 196 times, characterized by significantly affected by the typhoon or tropical low pressure system.On August 11, 2012, the local rainstorm is shear line precipitation, which because of weaker cold air and warm air southwest intersection; On June 30, 2012, the local rainstorm precipitation is local low pressure disturbance rainstorm. The two case has another major difference, case one no secondary circulation, but case two has obvious secondary circulation system. Through MPV analysis found that the development of MPV has an important relationship with precipitation, often corresponding negative MPV1 precipitation occurs, but executives are MPV1 occupy an important role in the constraints, that is, if executives are MPV1 large gradient, even if the underlying negative MPV1 great value, it may not have the precipitation occurs.The influence of different land surface scheme for local rainstorm is change intensity and the center position; Different land surface scheme led to simulate the surface energy flux distribution form bigger difference, the surface sensible heat and latent heat fluxes simulation on different land surface process scheme of sensitivity is not big. Change bureau ground mat surface properties can only change the precipitation of the local region, have little impact in other areas. Lei Zhou peninsula land have important influence for its local heavy rains, mainly impact the occurrence time of the precipitation, development and strengthen the rainstorm process.