摘要
利用盐城多普勒天气雷达和地面自动站等资料,对2006年8月6日下午发生在江苏盐城中北部地区的一次由强降水(high precipitation,HP)超级单体产生的大暴雨和龙卷过程进行详细分析。风暴回波演变的形态可分为"条状—肾形—弓状"3个阶段:在条状回波阶段,产生龙卷伴随强降水,中气旋在变粗的中段前侧生成,其内有一个垂直涡度约为8×10-2s-1的龙卷式涡旋特征(tor-nadic vortex signature,TVS),高层悬挂回波下有低小的有界弱回波区(bounded weak echo region,BWER),位于BWER之上高层17 km风暴顶为强烈辐散,辐散值约为1.2×10-2s-1;在肾状回波阶段,产生短时大暴雨,低层前侧有包含一个中气旋V字型入流缺口,其后是粗胖的高反射率因子钩状回波区,速度图上中气旋位于中尺度辐合线之中;在弓状回波阶段,产生短时暴雨,风暴减弱后与另外回波合并前侧又有中气旋生成,其后低层右后侧为较大的高反射率因子回波区。在上述3个阶段,该风暴具有HP超级单体风暴共同特征:中气旋、阵风锋位于前侧,强降水包裹着中气旋,沿着预先存在的东南风速辐合线移动。HP超级单体产生的主要天气背景是副热带高压边缘形势,一个东移的高空槽、强烈的热力不稳定和较大的垂直风切变。盐城中北部地区午后地面风场上形成的,与东南海风有关的一条南北向湿热边界层辐合线,对HP超级单体沿着此辐合线发展并维持长生命史有重要作用。
Based on the data from Doppler weather radar and automatic weather stations,a supercell case causing tornado and rainstorm,which hit the central and northern area of Yancheng,Jiangsu Province on the afternoon of 6 August 2006,is studied.The results show that this supercell is featured as a typical HP（high precipitation）：the gust front,V-notch,the large hook echo and the front mesocyclone.The evolution of this HP supercell can be divided into two phases：the independent developing phase and the complex phase.In the first phase,the cell generated tornado（accompanied by heavy rain） and storm rainfall.When tornado appeared,the main echo formed a long curve bandwith a small and lower BWER（bounded weak echo region） under the overhang and a strong divergence was probed at 17 km height at top of the mesocyclone.A TVS appeared in the front part of the mesocyclone with a vertical vorticity of 8×10^-2s^-1at 1.4 km height over the surface.When the storm rainfall occurred,the main echo＇s shape became a ＂kidney＂ and an inflow V-notch was near the mesocyclone which was wrapped in a convergent area.In the second phase,the weakened bow echo strengthened again by combining with an echo band from southern area of Yancheng,which produced another heavy rain.The HP supercell had a low centre of mass throughout the whole process and the top of the mesocyclones was under 0 ℃ which was at about 5 km height in most of the time.The analysis depicts that a south-north-extending convergent line of surface wind and the moisture brought by sea breeze exert significant effects on the development of the HP supercell.
出处
《大气科学学报》
CSCD
北大核心
2010年第3期285-298,共14页
Transactions of Atmospheric Sciences
基金
国家自然科学基金资助项目(40575014
40875029)
关键词
HP超级单体
中气旋
龙卷
大暴雨
阵风锋
辐合线
HP supercell
mesocyclone
tornado
high precipitation
gust front
convergent line
