风暴生命史雷达特征量反演

Convective Storm Life Cycle Parameters Derived from Radar Reflectivity Data

从风暴演变各阶段物理特征出发,基于多普勒雷达观测的三维反射率因子,定义物理量——单体重力势能。结果表明:单体重力势能是一个能够简洁、客观描述风暴单体整体强度的物理量;利用该物理量可描述单体生命史为发展和减弱两个基本过程;单体重力势能大小有助于辨别风暴类型和强度。同时,生成和分析了风暴单体演变各阶段的反射率因子垂直廓线,分析表明:在30～150km的雷达观测范围内,风暴单体的反射率因子垂直廓线(降水廓线)及其随时间的变化能较好地揭示风暴的垂直结构和生命史演变特征,但没有用重力势能那样简洁。

Weather radar is one of the important tools of severe storm warning. It is important to depict the density and evolution of whole storm using weather radar reflectivity data for storm identification and tracking. Therefore, based on 3-demension CHINRAD/SA radar reflectivity, cell gravity potential energy （CEPE）, a new physical parameter, is defined, which is relevant to storm life cycle. Its expression is derived and characteristic is studied. In addition, the vertical reflectivity profile of the cell is built and analyzed. The results show that the density of whole storm cell can be compactly and objectively described by the CEPE, and the cell evolvement trend is reflected by its change. If using CEPE to describe cell life cycle, there are two basic processes during the entire life cycle of the cell, namely developing process and weakening process. In spite of the overview singlepeak distribution pattern, sometimes there is a little pulse in the pattern which occurs mostly at developing phase. At mature phase, the value of the CEPE is marked different among different cell types. The largest is for supper cell, the second is for multi cell, and the least is for ordinary cell. Accordingly, cell type can be distinguished by CEPE to some extent. The characteristics of vertical reflectivity profile （VPR） of the storm cell are different from initiative to dissipated phases, which help to identify the evolution of the storm cell. But these differences can not be opened out to 150 km and in 30 km,as the effects of the earth curvature and radar blind area respectively. Comparing these two methods, it is obvious that the VPR is not as concise and objective as the CEPE.