The Wind Field Variational Assimilation Technique Of Doppler Weather Radar In Numerical Prediction Of Severe Convection Weather In South China

It is studied in this paper how to apply the wind field variational assimilation technique of Doppler weather radar in numerical prediction of severe convection weather in South China. Mainly focusing on 2 kilometer horizontal resolution , the CINRAD-SA Doppler radar data in Guangzhou has been made variation under the frame of GRAPES—3DVAR, with exception to obtain the initial field with high resolution and containing more local information to improve the forecast system of severe convection weather.We selected two severe convection cases of April 26th and May 7th in 2004 for variational assimilation analysis. It is found that the mesoscale numerical model (the horizontal resolution of GZHM is 14km) is likely to omit some relative small system or wrongly estimate the intensity of the mesoscale system for the deficiency of data. Variational assimilation of the radar data can availably provide more information with high resolution and more detailed structure of local systems. It has acloser depiction of the structure and intensity of mesoscale circulation. Using GRAPES fine grid model (2-3km horizontal resolution) to simulate severe convection weather process on April 26th in 2004, we found that fine model can definitely reflect many important characteristics of severe weather, forecast essentials such as the hour-to-hour precipitation and wind field were improved to some extent as compared to the operation trial. The initial field originated from variation of radar data can provide more perfect description to the structure and intension of mesoscale weather process." It has developed the model of predicting of severe convection weather in south china. We analyze the process of April 26 , 2004. In the vicinity of Zhujiang area, humidity of lower layer increased, temperature of ground surface maintained and temperature of higher layer decreased to some extent. The cumulative energy, due to the diversity of above and below troposphere, triggered by the latitudinal shear of wind, led to strong convection. It may be one mechanism of severe convection weather in wee hour of South China.