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利用NCEP 1°×1°的6 h再分析格点资料和气象台站实测降水资料,采用WRF中尺度数值模式,对2008年7月23日发生在山东日照市的一次大暴雨过程进行了数值模拟和诊断分析。结果表明,此次大暴雨是在副热带高压、高空槽、西南低涡和切变线的共同作用下发生的;低层强烈的水汽输送和水汽辐合使暴雨区大气湿层迅速增厚,为暴雨的形成提供有利条件,水汽通量辐合中心与暴雨的落区有很好的对应关系;低层辐合高层辐散的配置有利于对流发展和低层水汽向高空输送;强烈垂直上升运动为暴雨发生提供了动力条件;700 hPa的垂直螺旋度与相应时次1 h降水存在很好的相关;强降水时段,暴雨区上空形成了从低层一直延伸到对流层顶层的正垂直螺旋度柱,暴雨中心的降水峰值正好出现在正螺旋度中心出现时段,垂直螺旋度中心的大小及变化一定程度上代表了降水系统的强弱和变化。
Based on the 6 h reanalysis grid data of 1 ° × 1 ° by NCEP and the measured precipitation data of meteorological stations, a numerical simulation of a heavy rain event on July 23, 2008 in Rizhao, Shandong Province was carried out using WRF mesoscale numerical model. Diagnostic analysis. The results show that the heavy rain occurred under the combined effect of subtropical high, upper trough, southwestern vortex and shear line. The intense water vapor transport and water vapor convergence in the lower layer rapidly thickened the atmospheric wet layer in the heavy rainfall area, The formation of favorable conditions, water vapor flux convergence center and the rainstorm area has a good correspondence; low-level convergence of high-level divergence configuration is conducive to the development of convection and low-level water vapor transmission to the sky; strong vertical upward movement for the occurrence of heavy rain The vertical helicity at 700 hPa is correlated well with the corresponding hourly precipitation at 1 h; during the heavy precipitation period, the vertical helicity column extending from the lower layer to the top of the troposphere is formed over the heavy rain area, The peak appears exactly at the center of the positive helicity, and the size and change of the center of the vertical helicity represent the strength and variation of the precipitation system to a certain extent.