Studies On Method Of Torrential Rainstorm Forecast In Henan Province

The paper studied rainstorm from1961to2010in Henan, draw the conclusion that Henan rainstorm is increasing trend. Through the study of the temporal distribution and variation of rainstorm and heavy rainstorm, the paper predicted rainstorm variation trend and spatial distribution, which has guiding significance for the future rainstorm research.Based on the conventional observation data, MICAPS data, ECWMF and T213numerical forecast, FY-2satellite cloud picture data, the two rainstorm processes in Henan on July28—30,2007and July22—24,2010are diagnostic analyzed by using synoptic principles and synoptic analysis method. The results are as follows:(1) Two rainstorm processes occurred in the favorable weather background situation of Lake Balkhash upper trough, low vortex and shear line interaction. The "high east and low west" is one of the basic situations to produce rainstorm in Henan. The principal influence systems are subtropical high, the Tibetan high, upper and lower jet stream, low vortex and shear line.(2) The low-lever southwest jet provides moisture condition for the rainstorm occurrence; the upper westerly jet the rainstorm process provides a strong dynamic lifting condition for the rainstorm processes. The upper strongly divergent areas which on the right side of the upper level jet axis often correspond to the rainstorm center, the upper divergence t has important significance for rainfall forecast.(3) The main ground system in the two rainstorm processes are stationary front and cold front.(4) The rainstorm appears necessary condition in Henan is that the relative humidity at700hPa is greater than or equal to80%.(5) Two rainstorms moisture sources are different:one is the Indian Ocean; the other is the South China Sea.(6) There must exist negative moisture flux divergence center at700hPa in rainstorm process in Henan, and the center value is not less than-4×10-6g·cm-2·hPa-1·s-1.(7) The rainfall of rainstorm and heavy rainstorm is corresponding vertical velocity negative area at500hPa, which can be forecast indicators of rainstorm and heavy rainstorm.(8) The key to accurately forecast the rainstorm is accurate analysis of vertical wind shear.(9) The main clouds in torrential rainstorm are mesoscale convective monomer and mesoscale convective complex, convective clouds appeared at the same place again and again and maintained constantly under "the train effect", then the torrential rainstorm was caused. These indicators and technical can guide rainstorm forecast in Henan.(10) Using T213physical quantities and technology to establish the heavy rains forecast method and carry on the inspection, the method we used has a higher level on the torrential rainstorm forecast in Henan province and24hours to72hours forecast accuracy remained stable, it indicated that the forecast indexes form method of physical analysis are effective, and it has a good forecast ability to torrential rainstorm during the midsummer in Henan province.