盐城一次龙卷、短时强降水的地面中尺度分析和雷达回波特征

摘要

利用地面加密自动站和多普勒天气雷达资料,对2006年7月3日发生在盐城的龙卷和短时强降水等强对流天气过程进行了详细分析。结果表明：此次强对流天气发生的天气背景是江淮梅雨期暴雨形势,即高空东移的西风槽、中低空西南急流以及强烈的对流不稳定。地面中尺度涡旋的发展、维持为强对流天气的产生提供了持续强劲的上升运动;龙卷发生在非超级单体风暴中低层反射率因子梯度区上,在平均径向速度图上出现了明显的小尺度涡旋特征。另外,西太平洋副热带高压和赤道辐合带上活动的3个热带系统为短时强降水提供了超常的充沛水汽,短时特大暴雨发生在中低空急流增强到最强并开始减弱的时段内,与大于50dBZ的强回波面积的变化关系密切。%The tornado,short-term heavy precipitation and other convective weather in Yancheng City on 3 July 2006 are analyzed based on the data of dense surface automatic meteorological stations and Doppler weather radar.Results show that the weather background of the convective weather is Changjiang-Huaihe storm weather situation of the Meiyu,including the westerly trough eastward in upper levels,southwest jet stream in low-mid levels and strong convective instability.The development and maintenance of surface mesoscale vortex cause a continued strong upward motion for the convective weather.The tornado occurs in the large reflectivity gradient region in low-mid levels of the non-supercell storm,with a marked small scale vortex feature in the average radial velocity.In addition,three tropical systems in the western Pacific subtropical high and the ITCZ provide abundant moisture for the short-term heavy rainfall.There is a close relationship between the short-term heavy rainfall （occuring in a period of the increasing to the strongest,and to the beginning of decrease for the jet stream in low-mid levels） and the strong echo area larger than 50 dBZ.