The Evolution of a Meso-β-Scale Convective Vortex in the Dabie Mountain Area  

作　　者：徐文慧 倪允琪 汪小康 邱学兴 

机构地区：[1]National Meteorological Information Center [2]Chinese Academy of Meteorological Sciences [3]Wuhan Institute of Heavy Rain [4]Anhui Meteorological Observatory

出　　处：《Acta meteorologica Sinica》2012年第5期597-613,共17页

基　　金：Supported by the National Key Basic Research and Development (973) Program of China (2004CB418300)

摘　　要：The evolution of a mesoscale convective system （MCS） that caused strong precipitation in the northern area of Dabie Mountain during 21 22 June 2008 is analyzed, along with the evolution of the associated meso-β-scale convective vortex （MCV）. The mesoscale reanalysis data generated by the Local Analysis and Prediction System （LAPS） at a 3-km horizontal resolution and a 1-h time resolution during the South China Heavy Rainfall Experiment （SCHeREX） were utilized. The results show that two processes played key roles in the enhancement of convective instability. First, the mesoscale low-level jet strengthened and shifted eastward, leading to the convergence of warm-wet airflow and increasing convective instability at middle and low levels. Second, the warm-wet airflow interacted with the cold airflow from the north, causing increased vertical vorticity in the vicinity of steeply sloping moist isentropic surfaces. The combined action of these two processes caused the MCS to shift progressively eastward. Condensation associated with the MCS released latent heat and formed a layer of large diabatic heating in the middle troposphere, increasing the potential vorticity below this layer. This increase in potential vorticity created favorable conditions for the development of a low-level vortex circulation. The vertical motion associated with this low-level vortex further promoted the development of convection, creating a positive feedback between the deep convection and the low-level vortex circulation. This feedback mechanism not only promoted the maturation of the MCS, but also played the primary role in the evolution of the MCV. The MCV formed and developed due to the enhancement of the positive feedback that accompanied the coming together of the center of the vortex and the center of the convection. The positive feedback peaked and the MCV matured when these two centers converged. The positive feedback weakened and the MCV began to decay as the two centers separated and diverged.The evolution of a mesoscale convective system （MCS） that caused strong precipitation in the northern area of Dabie Mountain during 21 22 June 2008 is analyzed, along with the evolution of the associated meso-β-scale convective vortex （MCV）. The mesoscale reanalysis data generated by the Local Analysis and Prediction System （LAPS） at a 3-km horizontal resolution and a 1-h time resolution during the South China Heavy Rainfall Experiment （SCHeREX） were utilized. The results show that two processes played key roles in the enhancement of convective instability. First, the mesoscale low-level jet strengthened and shifted eastward, leading to the convergence of warm-wet airflow and increasing convective instability at middle and low levels. Second, the warm-wet airflow interacted with the cold airflow from the north, causing increased vertical vorticity in the vicinity of steeply sloping moist isentropic surfaces. The combined action of these two processes caused the MCS to shift progressively eastward. Condensation associated with the MCS released latent heat and formed a layer of large diabatic heating in the middle troposphere, increasing the potential vorticity below this layer. This increase in potential vorticity created favorable conditions for the development of a low-level vortex circulation. The vertical motion associated with this low-level vortex further promoted the development of convection, creating a positive feedback between the deep convection and the low-level vortex circulation. This feedback mechanism not only promoted the maturation of the MCS, but also played the primary role in the evolution of the MCV. The MCV formed and developed due to the enhancement of the positive feedback that accompanied the coming together of the center of the vortex and the center of the convection. The positive feedback peaked and the MCV matured when these two centers converged. The positive feedback weakened and the MCV began to decay as the two centers separated and diverged.

关 键 词：mesoscale reanalysis data mesoscale convective vortex mesoscale convective system evolu-tional mechanism positive feedback 

分 类 号：P426.6[天文地球—大气科学及气象学]