台风“海葵”(2012)登陆后西折蜗行诊断分析

The Diagnostic Analysis of the Westward Moving Path of Typhoon Haikui (2012) after Landing

利用地面高空常规探测资料、NCEP再分析资料、数值模式预报资料,针对2012年第11号台风"海葵"登陆后移动路径的突然西折蜗行和陆上的长久维持机制两大预报难点,从大尺度环流特征和物理场两方面进行了诊断分析。结果表明:(1)"海葵"登陆后由西北方向移动转为西折,是由于其北部东、西两环副高未能因低槽东移而完全断开形成北上的通道,西环副高对其西行又形成阻挡作用,使得"海葵"低压环流西折并在安徽省南部蜗行。(2)"海葵"移动方向前侧有正涡度平流中心,正、负涡度平流中心的连线与未来移向基本吻合,其中心沿着不稳定区域和高能区域移动,存在趋暖运动。(3)"海葵"登陆后大风速区呈逆时针旋转,低压环流的风场分布出现明显不对称,东风分量比西风分量大,风场结构中不对称的强风速区转移使西北移动的路径减速并西折。(4)西南风低空急流是"海葵"在陆上久留不消的重要水汽输送带。"海葵"高层与中纬度急流靠近,高空急流出口区的强辐散也有助于其在陆上的维持。(5)"海葵"登陆后较长时间位于对流层风速垂直切变经向梯度大值区中,其中心附近垂直风切变很小,这使得其衰减缓慢,维持时间长。此外,"海葵"登陆后经过较大水面及前期大降水区为其长久维持提供了潜热能源。

Based on the NCEP reanalysis data, conventional observation data and model output data, the large scale circulation and physical quantity field that impacted the moving path and maintenance of the typhoon Haikui after its landing are diagnostically analyzed. The results are as follows：（1） The subtropical high was not broken completely by the eastward trough, and its western parts obstructed the westward moving of Haikui after its landing, which induced the Haikui low pressure circulation turning westward along the south of Anhui with slow speed.（2） There was a positive vorticity advection center in front of the Haikui, and the center of Haikui moved along the unstable region and the high-energy region.（3） The wind region of Haikui presented obviously asymmetry, and the east wind component was greater than the west one, which caused the system west turning.（4） The low level southwest jet provided enough water vapor transportation, which made Haikui lasting for a long time after its landing. （5） The weak vertical wind shear in Haikui center and the latent heating provided by the large surface water body played important roles on the maintenance of the landing typhoon.