Statistical Analysis And Numerical Simulation Of Severe Convection Weather In Hunan Province

The severe convective weather in Hunan mainly includes strong thunderstorm, Short-time heavy rainfall, thunder wind, hailstone and tornado. They frequent destruction of property. The statistical analysis of severe convection weather and numerical simulation set the stage for the forecasting of the hazardous weather and the capacity of early-warning.The climate character of convective weather and the echo characteristics of radar in Hunan are described based on the circulation background of the weather system and the occurrence and development of convective, leading the following results.(1)The totally distribution trends of the frequency of hail in Hunan were the northwest more than the southeast, and the seasonal variation was obvious, most hail occurred in the spring. Moreover, the diurnal variation is also very obvious, most of the hail appears afternoon to evening. Radar echo features include three-body scattering, hook echo, bounded weak echo and high VIL values.(2) Most of thunder wind in Hunan was appeared in midsummer, and lots of them occurred at 16:00 in a day, the duration of them were 2 minutes generally. Except the same radar echo characteristic as hail's, thunder wind has another characteristic as bow echo, linear echoes, squall lines, low-level wind etc.(3) The rainstorm in Hunan occurred in mountain lakes was generally greater than the plains and hills in May, but north greater than south in June. And the radar echo has large-scale radar echo, incorporation echo, train effect echo, merge echo.Moreover, by using the mesoscale ARPS (the center for Analysis and Prediction of Storms) model which developed by CAPS (the center for Analysis and Prediction of Storms) of Oklahoma University, the typical severe convection cases happened in Hunan and their assimilative features and analog capacity through assimilation simulated experiments of three-dimensional radar data changes in absorption were studied, leading the following results:(1) Results from the ARPS 3DVAR assimilation test of the severe convection cases of March 21th in 2009 by the use of single Doppler radar show that the location and trends of echo after assimilation are more consistent with the disaster site, but the intensity of echo is weak. After the assimilation of radial wind, the significant changes of wind field have taken place. It has better correspondence between the maximum wind area and the strongest echo area and its direction of movement.(2) Results from the ARPS 3DVAR assimilation test of the the severe convection cases of May 5th in 2010 by the use of double Doppler radar show that the radar reflectivity was strengthened than the former, and it has better indication of area of strong rainfall. Furthermore, direct insertion of radial velocity could improve the initial wind fields with more small/meso scale information.(3)Though these two cases we can see that the results of adding two radar data for variational assimilation is better than single radar. The echo intensity and the wind field structure have been greatly improved. But adding more radar data for assimilation will achieve better results needs more further testing.