初值及物理过程对“98·7”暴雨预报结果的影响

Effect of Initial Data and Physical Processes on the Heavy Rainfall Prediction in July 1998

利用非静力中尺度模式系统(ARPS),对1998年7月20日至22日期间长江流域的低涡切变线及暴雨过程进行了模拟。探讨了对“98·7”突发暴雨的影响因子及改进预报的可能途径。初值的不完全是影响成功预报的重要原因之一。在利用尽可能收集到的资料,对初值进行了合理的处理之后,模式能较好地复制出7月20～22日24h降水及环流形势。利用模式结果,讨论了凝结潜热释放和行星边界层过程在低涡切变线维持中的作用以及云贵高原在低涡发生发展过程中的作用。此外,还对低涡及切变线的演变过程做了初步的分析,初步探讨了低涡切变线形势维持的可能机制。

The low-level vortex and shear line and the accompanying severe heavy precipitation in July 1998 are successfully simulated by using non-hydrostatic mesoscale model system (ARPS). The effect factors of heavy rainfall and the possible way to improve forecast are also studied. It is found that the incompletion of the the model initial data is one of the most important reasons for unsuccessful prediction of heavy rain. The simulated 24-hour cumulated rainfall and weather systems can be reproduced by the model as the initial field was treated reasonably by using all kinds possible observational data, including the significant level data. The function of the latent heat release, PBL process and terrain of the Yunnan-Guizhou Plateau is discussed according to the model results. In addition, the evolution of the low-level vortex and shear line is analyzed, the possible maintain mechanisms for such system are also discussed.