迎风坡暴雨预报中多普勒天气雷达资料两种散度反演方法的应用

Application of Two Divergence Inversion Techniques for Doppler Radar in Short-Term Heavy Rain Forecasting

简单介绍了由多普勒天气雷达径向风资料反演平均散度和径向散度的计算方法,以2004年7月11—12日暴雨过程为例说明两种散度在迎风坡暴雨跟踪、预报中的综合应用。分析结果表明:①平均散度可以作为降水跟踪、预测的背景场。降水出现之前,低层平均散度存在辐合;低层辐合加强或维持,整个区域降水将加强;辐合高度抬升到中层并维持,降水达到最强;辐合减弱并开始出现辐散,区域降水将逐渐结束。②根据径向散度的分布情况,可以提前2h以上预报强降水的落区。强降水落在径向辐合大值区后部的较弱辐合区内,且弱辐合区强度越强,未来降水强度越大。因此,综合分析平均散度和径向散度随时间的变化,可以跟踪、预测降水的发展演变,特别是可以给出暴雨的大致落区。

Two methods for retrieving the average divergence and radial divergence are introduced by means of the Doppler radar radial velocity data.Their application in rainstorm tracking and heavy rainfall forecasting is discussed,as an example,by a rainstorm process on 11 and 12 July 2004.The results indicate：（1） The average divergence field can be used as the background of rainstorm tracking and heavy rainfall forecasting.Before precipitation,there exists convergence at low levels averagely.If the convergence strengthens or maintains,precipitation will increase in the whole region.While if the height of the convergence lifts at middle levels and maintains,precipitation will be the strongest.If the convergence weakens or begins to become divergent at low levels,regional precipitation will gradually end.（2） According to the distribution of radial divergence,the area of heavy rainfall can be forecasted two hours ahead： the area of heavy rainfall will be within the rear weak convergence zone of the largest radial convergence area;the stronger the intensity weak convergence zone is,the greater the rain intensity is.Therefore,by means of the comprehensive analysis of average and radial divergence changes along with time,the development and evolution of precipitation can be tracked and forecasted,especially,the area of heavy rainfall can be located roughly.