摘要
利用雷达、加密自动站、NCEP再分析资料和常规观测资料,对2011年11月4日发生在江苏中北部由超级单体产生的短时强降水过程,经分析表明:(1)本次过程中500 hPa为西南暖干气流,上下层温度平流差动不明显,上下层湿度平流差动是前期位势不稳定建立的主要原因。(2)超级单体风暴低层强烈的后侧入流,不断为其输入暖湿气流,其前侧为强烈的上升气流,而高空有较强的后向流出。在这种流场的作用下,超级单体风暴的发展得到加强和维持。(3)对流首先在700 hPa相对湿度梯度大值区与地面中尺度辐合线相交处被触发,整个过程中强对流回波出现在地面中尺度辐合线附近,并伴随其东移。东移的地面辐合线与盐城东部局地生成的对流风暴所造成的地面辐散出流相遇,演变为一条新的地面辐合线,地面辐合显著增强,导致短时强降水的发生。中尺度地面辐合线的移动和增强在这次超级单体风暴过程中起到了触发和维持、加强的作用。(4)对流发展初期,地面辐合区对应着未来对流回波生成区域,有很好的超前性;随着对流发展,地面负散度大值区与对流回波区逐渐重合,当散度场出现临近正负散度中心对时,对流发展达到最强。
Radar, automatic weather station and the NCEP data are used to investigate the mesoscale convective system which caused the severe convection weather process on November 4,2011 in the north- ern part of Jiangsu. Results showed that ： （ 1 ） the fact that 500 hPa is southwest warm and dry airflow, lack of upper and lower differential advection of temperature, upper and lower differential advection of mdisture are the main reasons for establishing the potential instability of early stage. （2） Supercell storm can develop, strengthen and maintain because of its strong rear inflow as continuous source of warm air at the lower level and the occurrence of strong rising air currents in its front and because of strong outflow at the upper level. （ 3 ） Convection Strom is triggered firstly in a the areas where the 700hPa relative humidi- ty gradient maximum value zone intersects the surface mesoscale convergence line. During the whole process, strong convective echo appears near the surface mesoscale convergence line and moves eastward. The surface flow divergence caused by the local generation of severe convection storm in eastern part of Yancheng can meet with the eastward surface convergence line and evolves as a new surface convergenceline, surface convergence increases significantly, but moving speed decreases significantly so it leads leading to strong precipitation. Mesoscale surface convergence line movement and enhancement in this supercell storm process can play the the role in triggering and maintenance. （4）In convection generating and development phase, surface convergence zone corresponds to a future generation area of convective echo and acts as a leading factor. With the development of convection, ground negative divergence value zone and convective echo area gradually coincides. When divergence appears near the positive and nega- tive divergence center, the development of convection reaches the strongest stage.
出处
《气象科学》
CSCD
北大核心
2012年第6期685-693,共9页
Journal of the Meteorological Sciences
基金
江苏省气象局科研开放基金项目(KZ201102)
江苏省气象局青年基金项目(Q200904)
关键词
强降水超级单体
湿度平流差动
地面辐合线
地面散度场
Severe supercell
Differential moisture advection
Surface convergence line
Surfacedivergence field
