The Sensitivity Study Of Terrain In The Beijing "721" Extreme Rainfall Based On LAPS

The Local Analysis and Prediction System (LAPS) and Weather Research and Forecasting (WRF) Model were used in the high resolution numerical simulation, which assimilated automatic stations, radar, radiosonde and satellite observations. ECMWF reanalysis data and FengYun satellite infrared brightness temperature data were used to analyse the synoptic situation of Beijing "721" extreme rainfall. The numerical simulation can accurately reproduce the precipitation distribution of warm sector and the position of cold front, as well as the formation, evolution and organization of the mesoscale convective cells. The results show that:Hetao vortex, cold front, subtropical high, upper jet, lower jet and typhoon Vicente have significant impact on the extreme rainfall event.This paper designed a 6-set terrain sensitivity test, detailed analysis of Beijing and its surrounding regions of complex terrain and "721" interaction of storm, comparing different altitude terrain on "721" heavy rainfall distribution, the impact of land surface temperature and surface wind field. Results showed that:(1) falling terrain height, topographic convergence line of weakening in the Beijing area, warm and humid steam penetrate deeply into strong precipitation decrease, local total precipitation decrease late cold fronts moving rapidly eastward, the temperature dropped significantly. (2) the terrain height increasing cyclonic surface wind field divergence in Beijing weakened, topographic convergence line has actually strengthened more water vapor being intercepted, strong rainfall enhancement, late cold front moves blocked smooth change local surface temperature, warm air heating continuous conveying and tall terrain, local surface temperature rose. (3) terrain height rose to must degree, ground wind field cyclone sex spoke collection was weakened, terrain spoke collection line was enhanced, and to Southwest extends, air quality stacked increased, produced strong of Council to northeasterly winds, vapor conveying Center with of South moved, Council to precipitation significantly declined, late with warm wet airflow conveying weakened, air quality stacked reduced, northeast wind weakened, vapor conveying Center again moved to Beijing area, Council to precipitation significantly rose.