华北高空槽强降水过程的数值模拟及分析

Numerical simulation and diagnostic analysis of a heavy rain process caused by upper trough in north China

利用新一代中尺度数值预报模式WRF,对2008年8月20—21日华北地区的一次高空槽过境造成的大范围强降水过程进行数值模拟,并进行诊断分析。结果表明:高分辨的WRF模式可以很好地模拟出本次高空槽强降水过程;槽线降水沿地面低压带中心狭长带状分布;近地层比湿平流的变化对强降水产生和演变起至关重要的作用;700 hPa上升速度、700 hPa水汽通量散度辐合区与降水的强度和落区配合较好;相当位温θe的空间分布呈"V字型漏斗"结构,不稳定能量主要积聚于槽线附近中低层等θe线逆向折叠地区和强降水爆发前低层的θe逆温中。最后讨论了高空槽强降水的一种物理演变机制。

Numerical simulation of a large-area heavy rain process caused by upper trough in north China on August 20—21,2008 was made with the new generation mesoscale numerical model WRF.Then the model outputs were used in diagnostic analysis.The results indicate that the WRF model of high spatial and temporal resolution can reproduce this heavy rain process.The precipitation caused by upper trough is narrow and long and was distributed along with low-pressure center on the ground.Specific humidity advection change in surface layer is a very important factor of growing heavy rain.The 700hPa ascension velocity,the 700 hPa moisture flux convergence can reflect the intensity and location of this rainfall quite well.Potential equivalent temperature θe presents ＂the V funnel style＂ structure,unsteady energy mainly accumulates in the region where θe isoline was contrarily folded in the trough neighborhood or θe inversion appeared in the low layer before strong precipitation.Finally,the physical evolution mechanism of this heavy rain process caused by upper trough has been discussed.