2012年7月山东接连两次大暴雨过程对比分析

Contrast analysis of two successive torrential rain processes over Shandong in July 2012

利用常规观测资料、地面自动站资料、多普勒雷达风廓线数据、卫星云图及NCEP 1°×1°再分析资料,对2012年7月8日和10日接连发生在山东省的两场大暴雨过程进行对比诊断分析。结果表明:前一过程发生在副热带高压稳定的环流背景下以及不稳定能量增大的过程中,后一过程发生在副热带高压减弱南退的环流背景下以及不稳定能量释放的过程中;暴雨区上空低空急流和垂直运动强烈发展以及对流层中低层辐合、高层辐散的典型配置是两次过程发生共同的有利大尺度环境条件,不同的是,前一过程强降水强度与落区同强垂直上升运动、低空强辐合及高空强辐散、水汽通量辐合中心相一致,后一过程这种对应关系不如前一过程好;西南急流强烈发展对应两次过程的强降水时段,后一过程西南急流发展高度低于前一过程,其风速却比前一过程强得多,降水结束时后一过程冷空气下传速度比前一过程更快、高度更低;后一过程云顶温度更低,对流系统发展更高,云顶温度低于-70℃中心维持时间较长,强降水出现在云顶温度低值中心及其梯度大值区内,这对强降水临近预报具有较好的指导意义。

Based on conventional observation data, the surface observation of automatic weather station, wind profile data from Doppler ra-dar, satellite images and NCEP 1°× 1° reanalysis data, the contrast analysis for two successive torrential rain processes occurred in Shandong province on 8 July and 10 July 2012 is made. The results indicate thai the former process occurs against the circulation background of the subtropical high pressure continuously strengthened and unstable energy increased, and the later process takes place against the circulation background of the subtropical high pressure weakened and withdraw towards south as well as unstable energy released. The common large scale environmental conditions of the two processes include that the vertical motion and the low-level jet developed intensely over the torren-tial rain area and it has divergence at the upper-level, convergence at the middle and lower level. There are differences between the two pro-cesses. In the former process, intensity and distribution of severe precipitation is consistent with strong vertical upward movement, strong con- vergence in the low-level, strong divergence in the upper-level and water vapor flux convergence center. But in the latter process, the consis-tence mentioned above is poorer than that in the former one. Strong development of southwest jet is corresponding to the periods of severe pre-cipitation in the two processes. Development height of southwest jet is lower, the wind is much stronger, and when severe precipitation ended the downward dissemination speed of cold air is faster and the height of cold air is lower in the latter process than that in the former one. It has a certain prediction significance for severe precipitation nowcast that with lower cloud top temperature, higher development level of convec-tion system, longer continuance of cloud top temperature center below -70 ℃ severe precipitation emergences in the low value center and in the great gradient zone of cloud top temperature in the latter process.