2015年7月29—31日山东地区强降水过程的诊断分析与数值模拟

目的]为深入探讨山东地区夏季强降水的原因和机理,给暴雨模拟及预报分析提供有价值的参考,方法]利用常规观测资料和WRF模式对2015年7月29—31日山东地区一次典型强降水过程进行诊断分析和数值模拟。结果]结果表明：(1)此次过程是由东移的西风槽和低层的切变、低涡共同作用造成的,系统的位置及移动路径与降雨区的位置及移动非常一致。(2)WRF模式能较好的模拟出此次过程的天气形势,雨带的位置和范围与实际情况基本一致。(3)分析850 hPa水汽通量和水汽通量散度垂直剖面,可见两个水汽来源,西南急流左侧有切变和低涡,强的低层辐合配合较大的水汽通量,存在强烈的水汽辐合,大量水汽持续辐合上升,为此次大暴雨提供了充足的水汽。结论]此次过程是山东省汛期比较典型的强降水天气,高低空系统配置和不稳定条件非常有利于强对流天气的发展。WRF模式高时空分辨率的模拟结果弥补了常规观测资料和再分析资料时空分辨率方面的限制,有助于更好地分析和理解此次强降水过程。

Diagnostic Analysis and Numerical Simulation of a Heavy Rainstorm Process in Shandong

To discuss the cause and physical mechanism of summer heavy rainstorm in Shandong Province, and provide valuable reference for the simulation and forecasting analysis of strong rainfall, the heavy rainstorm process on July 29—31 2015 in Shandong was simulated and diagnosed by the conventional observation data and WRF model. The results showed that: (1) this heavy rainstorm was caused by the interaction of eastward westerly trough and vortex, shear line in lower troposphere layer, the location and movement of weather systems showed a good agreement with rainstorm area; (2) the WRF model could simulate the weather system quite well, while the simulated location and range of rain belt were basically identical with the actual situation; (3) two sources of water vapor were discovered through analysis of water vapor flux at 850 hPa and the vertical section of water vapor flux divergence, and there were shear line and vortex on the left side of southwest jet. Strong low-level convergence cooperated with large water vapor flux, which caused strong water vapor convergence. The sustained convergence and upward movement of large water vapor provided sufficient moisture for the heavy rainstorm. This process was a typical heavy rainstorm at flood season in Shandong, the coordination between weather systems at the upper and lower troposphere together with instability conditions were very beneficial to the development of severe convective weather. The simulation results of WRF model could make up the shortage of conventional observation and reanalysis data in temporal and spatial resolution, and be helpful to analyze and understand the heavy rainfall process better.