2012年初春粤北一次少见高架雷暴过程的分析

Analysis f a Rare,Elevated Thunderstorm in Northern Guangdong in the Early Spring of 2012

利用常规观测资料、地面中尺度自动气象站资料以及NCEP再分析资料,分析了2012年2月27日广东发生的一次罕见高架雷暴天气过程的特点及成因。结果表明,这次出现在低层冷高压控制下地面冷锋后部并伴有短时强降水、雷电和冰雹的强对流天气过程,是一次典型的"高架雷暴"过程。与从地面发展的普通雷暴不同的是,强对流天气发生时,近地面层大气层结稳定,低空有逆温层存在,暖湿空气是从逆温层以上开始抬升的,强对流天气落区与850 hPa切变线有较好的对应关系。中高层西风槽东移南压,850 hPa偏南急流的建立和显著增强,为此次高架雷暴过程提供了有利的环流背景。近地面层冷空气补充南下迫使低层暖湿空气抬升,配合高空槽前辐散气流的抽吸作用以及广东上空有利的大气动力、热力不稳定条件,是此次高架雷暴过程形成的原因。

Using conventional observations, data from surface mesoscale automatic weather stations and NCEP reanalysis, this work studies the characteristics and causation of a rare elevated thunderstorm that took place on February 27, 2012 in Gnangdong province. The results are shown as follows. This severe convec- tion is a typical elevated thunderstorm that occurred at the rear portion of a surface cold front in the control of a low-level cold high and was marked by short and intense rainfall, lightning and hail. Different from a regu- lar thunderstorm that evolves from the surface, the severe convection happened with stable atmospheric strati- fication near the surface layer and a low-level temperature inversion. The warm and humid air began its as- cent from above the inversion layer and the convection weather matched well with a shear at 850 hPa. The eastward and southward shift of a westerly trough at the mid- and higher-level and the establishment and sig- nificant enhancement of a southerly jet stream at 850 hPa are favorable background circulation for this elevat- ed thunderstorm. Its genesis was attributed to the follow-up supply of cold air advancing southward in the near-surface layer that forced low-level warm and humid air to ascend, the pumping effect of diverging air- flow before an upper-level trough, and the dynamic and thermodynamic instability of the atmosphere above Guangdong.