【摘要】 通过利用观测资料和中尺度数值模拟结果,对2002年6月18~19日(“02.6”)的一次梅雨锋暴雨β中尺度系统结构和演化及其发展机理进行了研究,分析发现:(1)此次暴雨过程发生在500 hPa东亚大槽不断加深发展的阶段,也是中纬度大气长波调整的时期。东亚大槽后的冷空气和副热带高压前缘的暖湿气流在江淮流域交汇为此次暴雨的产生提供了有利的大尺度条件。同时,对流层低层不断加强的西南气流为此次暴雨过程提供了有利的水汽条件。(2)1小时观测的降水量和TBB的分析表明,此次暴雨的产生主要是由于β中尺度对流云团发展分裂的结果。(3)中尺度模式MM5V3对此次暴雨过程的数值模拟表明:模拟结果较好地再现了观测的和客观分析的天气事实,模拟的1小时降水量与观测的结果对应得较好,β中尺度对流云团位于切变线的右侧西南气流中,但是并没有明显的中尺度环流系统与之对应,这主要是由于细网格域中的模拟结果是各种尺度大气场叠加的结果,β中尺度对流系统的环流系统被掩盖在其中。(4)多重滤波方法和消除趋势方法并没有分离出与β中尺度对流云团相对应的环流系统,区域平均方法得到的中尺度扰动特征可以很好地解释β中尺度对流云团的发展和演变。区域平均法得到的中尺度扰动场的分布表明,两个β中尺度对流云团位于对流层低层鞍型场的膨胀轴上和对流层高层的中尺度反气旋式环流中。大气低层和高层的相互作用、低层中尺度扰动低涡和鞍型场的相互作用,以及对流发展过程中动力和热力的相互作用促进了中尺度低涡的发展。(5)非线性平衡方程的诊断表明,β中尺度系统的发展与非线性平衡方程残差ΔNBE的发展变化密切相关,β中尺度系统发生发展是动量场和质量场之间出现的不平衡释放的结果。更多还原

【Abstract】 The structure and evolution of the meso-β scale system during 1819 June 2002("02.6") Meiyu front rainstorm are analyzed using the observed data and the high-resolution output from the numerical simulation.The major conclusions as follows:(1) The observed analysis indicates that the rainstorm event developes during the deepening phase of East Asian trough at 500 hPa,and cold air behind the trough meets the warm and moist flow ahead of the subtropical high in the Yangtze RiverHuaihe River basin,which provided favorable large scale condition for the rainstorm.In addition,the rainstorm was associated with the intensification of the southwest flow in the lower troposphere.(2) The variation of TBB and observed hourly precipitation indicate that the rainstorm had close relation with the development of meso-β scale systems.(3) The mesoscale model MM5v3 can successfully reappear the observed and objective analysis facts for this case,and the simulated results also indicate that there was no obvious mesoscale circumfluence consistent with two centers of precipitation.Simulated results in D02 are superimposed by multiple-scale atmosphere where mesoscale circulation are hidden.(4) The separated mesoscale field with multiple filter method and removal of trends method cannot obtain obvious circulation associated with strong rain.The(analysis) of separated mesoscale field with area average method shows that two meso-β scale systems are located on the dilatation axis of saddle in the lower troposphere,and also located in the mesoscale anticyclonic circulation in the upper troposphere.The interactions of atmosphere between low and high levels and between low vortex and saddle inspire the development of meso-β scale systems.(5) The diagnoses of the residual of the nonlinear balance equation show obvious evidence of strong imbalance is associated with meso-β scale systems,which means mesoscale system would be generated through the adjustment process by relieving the imbalance between mass and momentum.更多还原