循环同化雷达资料对一次飑线系统临近预报的改进作用

利用WRF(Weather Research Forecast)模式及其3D-Var(Three-Dimensional Variational assimilation)变分系统,针对2017年7月7日一次飑线进行了雷达资料的循环同化敏感性试验.结果表明:以循环同化雷达资料至飑线成熟期时刻的试验预报效果最好,主要原因...

Improvement of nowcasting for a squall line using cycling assimilation radar data

Using the Weather Research Forecast (WRF) model and the Three-Dimensional Variational (3DVar) assimilation system, numerical sensitivity experiments were conducted to examine the performance of using radar data cycling assimilation to predict a squall line event in the surrounding areas of Beijing on July 7, 2017.Among the experiments, the best prediction occurred when the squall line reached the mature period with the use of the cycling assimilation of radar data.The main reason is that with the use of the cycling assimilation of radar data, the forecasted low-level northwesterly cold air is relatively strong, which leads to strong low-level wind shears.This is favorable for the maintaining of the squall line's development, in conjunction with strong thermal instability conditions.The comparison of 7 sensitivity experiments showed that for single radar data, the timing of assimilation is more important.The assimilation of radar reflectivity data at the mature stage of the squall line can improve the low-level thermal stratification and provide unstable energy for the development of the squall line.For cycling assimilation, the flow fields can be well modified through the observation influence and the thermodynamic adjustment of the model itself, which provides sufficient dynamic conditions for the continuous development of the convective system.