The causes of a gale and the monitoring system for severe convective weather over the Bohai bay
Based on TBB data from FY-2E satellite, the weather radar products,, ocean model products, lightning data, meteorological observational data at island stations, and offshore platforms,,the causes of the severe convective weather over the Bohai bay occurred from 01:00 a.m.to 06:00a.m, on 1st September in 2011 have been analyzed synthetically, and the forecasting ability of the numerical products were also tested. The results show that under the unstable conditions of shear line and stratification at 925 hPa, the cloud clusters of p-meso-scale system located at the south of Yanshan Mountains can conduce to redevelopment of the multi-cell storm at the westerly jet stream at 500hPa, and it will cause the severe rainfall and the hail weather within the short term. When the main part of the mesoscale system moves to the ocean, the storm strength have less change. With the interaction of the downdraft behind the multi-cell storm and downward momentum of the cold air behind it, the northeasterly wind component can be increased rapidly over the Bohai sea. The synchronous monitoring show the TBB in the mesoscale pixel is from -25 to -65℃, and the severe-weak transformation time of the convective cloud cluster is 3-6 hours from north to south along the west coast of the Bohai Sea. When its intensity weakened, it turns quickly to the northeast coast. The radial velocity diagram in three weather radars have successively detected the temporal and spatial characteristic of low-level jet stream at the northeast direction which is similar to the bovine eye. The momentum descending of the low-level jet stream could be inverted by the vertical wind profile, which is consistent with the data from island meteorological observatory and offshore platforms. When the wind turns to northeastern in central and south sea, there exists a time interval for about 3-4 hours. There is an obvious horizontal and vertical shear through radiosonde data at 20:00 p.m.. The value of K index is 33℃, the SI index is -3.8℃, and the convection effective potential (CAPE) is 1555 J/kg. The K index from the mesoscale numerical products within 3 and 6 hours and the dynamic simulation of the convergence line over the sea are relatively consistent with the pixel in the mesoscale TBB and the moving direction of the radar echo, but the windspeed is less by 10-12 m·s-1.
severe convection of Bohai seamesoscale monitoringsuperposing of northeast wind componentpredictability factor
国家科技期刊平台
NSTL
万方数据
维普
