中文摘要：

应用NCEPFNL 再分析资料及位涡分离反演等方法，对华南沿海2011年7月15-18日持续暴雨过程中季风槽与中尺度对流系统的相互作用进行了研究，主要针对暴雨发生期间季风槽气旋性涡度向上发展的机理及其对季风槽维持发展和中尺度对流系统活动的影响进行分析。结果发现，季风槽的中尺度对流系统发展于弱斜压性环境中，大多在槽东西两端涡度中心区发展最强。南侧盛行的西南低空急流为对流反复发生提供了对流发展的“可维持性”条件，是对流得以组织发展成为中尺度对流系统的重要原因。涡度收支诊断表明，季风槽气旋性涡度生成主要由中尺度对流系统低层辐合引起。位涡分离反演结果证实，季风槽气旋性环流增强主要由与中尺度对流系统潜热加热相关的扰动位涡造成，并随着中尺度对流系统加热峰值高度升高而向上发展，是大尺度环流对中尺度对流系统潜热加热动力响应的结果。在季风槽东西两端，由于中尺度对流系统发展强烈且持续，具有更高的加热效率，引起的气旋性涡度向上发展最为明显。其结果可引起中尺度对流系统西南一侧向北非地转风发展，并在地转偏向力作用下增强西风，维持低空急流的发展，为对流反复发生提供条件。这些都说明季风槽大尺度环流与中尺度对流系统相互作用在中尺度对流系统和持续暴雨形成过程中有重要作用。

英文摘要：

By using the gridded analyses from the NCEP FNL and the methods including the piecewise potential vorticity inver-sion （PPVI）,interactions between the Monsoon Trough （MT）and Mesoscale Convective Systems （MCSs ）during the persis-tent and torrential rainfall event occurred along the Southern China coast on 15-18 July 2011 were examined with the focus on mechanisms responsible for the upward development of MT＆#39;s cyclonic vorticity and their influences on the MT persistence and MCSs activity.The results show that the MCSs development within the MT was not baroclinic in nature,most of them inten-sively developed in MT’s eastern and western sections with high concentration of vorticity.It was the southwesterly Low Level Jet （LLJ）over south of MT to provide an environment of convective＆quot;sustainability＆quot;to support the reoccurrence of convection and development of MCSs.The vorticity budget analysis shows that vorticity generation within the MT was contributed mainly by the convergent effect associated with the MCSs low- level confluence.The PPVI results confirmed that the intensification of cyclonic circulation over MT was largely attributed to the mid- to low- level PV perturbations associated with MCSs condensa-tion heating,and as the vertical height of MCSs peak heating elevated this kind of intensification developed upward,indicative of a result from large-scale dynamical response to the development of MCSs.Especially over eastern and western sections of MT,where MCSs development presented intense and persistent,latent heating was highly efficient,the upward development of MT’s cyclonic circulation was the most significant.As a result,it led to northward ageostrophic flows genesis southwest of MCSs,and through the Coriolis torque,the westerly wind speed over LLJ increased,which providing a favorable condition for the development of LLJ and reoccurrence of convection.All these evidences suggest that interactions of the large-scale MT cir-culation and MCSs exert pivotal influence on