应用雷达产品计算风暴相对螺旋度

风暴相对螺旋度（SRH）反映了一定气层厚度内环境风场的旋转程度和输入到对流体内环境涡度的多少，对雷暴、龙卷和大范围暴雨的分析与预报有一定的实用价值。首先探讨了由多普勒天气雷达提供的垂直风廓线（VWP）产品计算SRH的方法和步骤。根据此方法，分别计算、分析了暴雨、冰雹、大风三个天气个例的SRH。结果表明：SRH与大面积降水过程的暴雨雨强有很好的对应关系，降水强度的变化滞后SRH强度的变化约半小时左右，可以由SRH大致估计降水加强及消亡的时间；SRH对尺度非常小的冰雹、大风等强对流天气有提前10～20分钟的预报作用。应用VWP产品计算出的SRH，可以作为实际业务工作中暴雨、冰雹、大风等强对流天气的预报因子，给预测人员预报强对流天气提供宝贵时间。

Calculation of Storm Relative Helicity with Radar Products

Storm relative helicity(SRH) reflects eddies in environment wind field and surrounding vorticities inputted into convective cell in an air layer, which is useful to analyze and forecast thunderstorm, tornado, large-area heavy rainfall as well. A method and steps of calculating SRH are presented, first, with Doppler radar vertical wind profile (VWP) product. Then, the SRH of three cases of heavy rain, hail, gale are discussed. Results indicate that the SRH is well corresponding to the intensities of the heavy rain in large area, the change of intensities lags the SRH change about 30 minutes, the time of precipitation strengthening or disappearing, therefore, can be approximately estimated by it. In addition, the SRH has effectivity about 10 to 20 minutes ahead to forecast micro-scale hail and gale, and then the SRH calculated with VWP can be used as a forecast index for strong convective weather such as a heavy rain, hail, gale, etc.