中文摘要：

利用观测资料和高分辨率的模拟资料研究了发生在江淮流域梅雨期的2007年7月8日的一次无层状云（NS）线状对流系统。观测资料分析表明,NS对流线在热低压和冷高压之间的梅雨锋附近发展起来。之后,梅雨锋南侧低压向东南方移动,受到武当山的地形作用,北侧冷高压南移受到阻挡,高低压之间强迫减弱,系统在向东南方向移动的过程中减弱。WRF模式成功地模拟此次过程,利用模拟结果分析了NS线状对流线在形成阶段、成熟阶段和减弱阶段的结构特点。在系统的成熟阶段,前部是向后的入流引导的上升气流,气流在斜升过程中在中层遇到对流后部入流,一部分形成了对流区下层的下沉运动,另一部分上升气流则与中层及高层后向入流一起继续向对流层高层的系统前方运动。通过2009年6月3日弓状回波（BE型）对流内部结构的对比分析,揭示了NS的结构特征以及系统没有或较少产生层状云的原因可能是后部中层以上的后向入流的阻碍作用。

英文摘要：

A convective line with no stratiform precipitation（NS） during a Meiyu period, which occurred over the Yangtze and Huaihe River Basin on July 8, 2007 was studied by using observational and high-resolution numerical simulation data. Based on the observational data, the NS system first developed between a hot low pressure（HLP） and a cold high pressure（CHP） near a Meiyu front. Then, a low pressure located on the southern rim of the Meiyu front moved southeast, while the position of CHP changed slowly due to the orographic obstruction of the Wudang Mountain. Both the force and system intensity became weaker when moving southeast. The structure characteristics of the NS system during its formation, mature and weakening stage were simulated successfully using the WRF model. During the mature stage, the slant upward flow, led by the backward inflow in the front of the convective line, encountered with a middle-level inflow in the rear of this system. The updraft axis was divided into two parts after entering the convection： one part turned into downdraft in the low level below the convection, and the another part, which was combined with a middle-upper-level backward inflow, became a middle-upper-level forward outflow. Comparing the structural characteristics of the NS system during its maturing stage with a bow-echoes（BE） system occurring on June 3 2009 revealed that the backward inflow in the middle- and upper-level, acting as an impediment to the convective system, was responsible for the absence of or less stratiform clouds in the NS system.