利用风廓线雷达资料分析一次强降水过程的风垂直切变特征

Analyzing the vertical wind shear characteristic of a severe rainfall using wind-profile radar data

联合应用5部风廓线雷达、多普勒天气雷达组网观测资料,并结合海河流域自动气象站资料详细分析了2012年7月21日海河流域强降水发生、发展过程中温度场、风场演变特征。结果表明:这次强降水天气具有明显的中尺度天气特征,强降水主要发生在露点温度梯度区内。低空急流指数变化对短时强降水的峰值有一定的指示作用,它的快速增加意味着强降水将要开始。垂直风切变对短时强降水的形成具有参考价值:降水开始前,2 500—3 000 m的风速和风切变首先开始增大,之后大风向1 000 m以下扩散,风切变梯度增强预示着短时强降水开始;1 000—1 500 m风速迅速减小,高层也随之减小,强降水趋于减弱或结束。风廓线雷达中风向风速的变化能够指示系统的过境时间,以上结论对预报强降水的起始及降水的持续时间具有使用价值。

In the article,we analyze the occurrence and development of the intensive rainfall along Haihe area on21July2012using thecombination of data from5wind profiler radars,Doppler weather radar network and weather data from auto-weather stations along Haihe area.The study reveals that the intensive rainfall carries obvious characteristics of the mid-range weather systems in which the occurrence ofrainfall is often in the gradient zone of the dew point temperature.The low jet index change is indicative to the peak value in the short-termintensive rainfall,i.e.,its fast increase means the beginning of the intensive rainfall.The vertical wind shear is of reference value to theshort-term intensive rainfall.That is,prior to the rainfall,the wind speed and wind shear begin to increase at middle and low levels(2500-3000m),followed by the strong wind spread to the lower level(1000m).The increase of the wind shear gradient predicts the beginning of theshort-term intensive rainfall.When the wind speed at low level(1000-1500m)reduces quickly as that in the higher level,the intensiverainfall weakens till its stop.The above features are applicable in forecasting and decision making for intensive rainfall.