地形对登陆热带气旋“黄蜂”(2002)强度影响的模拟研究

A Modeling Study of the Impact of Terrain on the Intensity of Landfalling Tropical Cyclone Vongfong (0214)

以“目标登陆台风外场试验研究”(CLATEX)项目的目标热带气旋“黄蜂”为对象 ,在用高分辨数值模式模拟其近海加强和登陆减弱过程的基础上 ,通过 5组对比数值试验 ,从定量和时间演化角度细致地分析了热带气旋周边海陆和地形分布对热带气旋强度的影响及其机理。分析表明 ,华南西部地理因子 (地形、粗糙度、海陆分布等 )对热带气旋强度变化具有重要影响。华南西部地形的存在 ,有利于低层弱冷空气向南侵袭 ,从而激发对流发展 ,使气旋迅速加强 ,是“黄蜂”近海加强的关键原因 ;登陆后冷空气切入造成的稳定层结抑制了对流发展 ,阻断了对流潜热能源 ,是“黄蜂”登陆后迅速减弱的重要原因 ;华南西部真实地形下的地表摩擦效应是“黄蜂”登陆后迅速减弱的重要原因之一 ;南海热带气旋区的地表热交换以潜热输送 (蒸发 )为主 ,其量值一般是感热输送的 5～ 10倍 ;洋面热交换与气旋强度间存在正反馈关系 ,符合热带气旋发展的“WISHE”(风引起的表面热交换 )机制观点 ,即“WISHE”可能是南海热带气旋发展的一种重要机制。

Taking the target tropical cyclone (TC) Vongfong of 2002 Chinese Landfall Typhoon Experiments (CLATEX) as object, the impact and its mechanism of sea-land distribution and terrain on TC intensity change are analyzed in detail from quantitative and temporal evolution points of view, based on the successful high resolution simulation of inshore intensification and weakening after landfall, and through 5 groups of numerical experiments, of Vongfong. Analyses show that terrain factors (terrain height, roughness length, sea-land distribution) in the western part of South China have important impacts on TC intensity change at landfall. The intensity change of Vongfong before and after landfall is closely related to the existence of the actual terrain in the western part South China, which is in favor of the southward invading of lower level cold air, inspiring convection and rapid intensification of TC, which is the key reason of inshore intensification of Vongfong. The cut-in of cold air into TC in lower atmosphere after landfall stabilizes the stratification and restrains convection, which is a key reason of Vongfong decay after landfall. While the friction effect under real terrain is one of the most important reasons for Vongfong decay after landfall. Moreover, the surface heat exchange relies mainly on latent heat transportation (evaporation), which is generally 5-10 times of the amount of sensible heat trans portation, in the South China Sea TC area. And the sea surface heat exchange has the positive feedback relation with TC intensity, which satisfies the “WISHE' (wind induced surface heat exchange) suggestion, i.e., “WISHE' may be an important mechanism for the South China Sea TC intensification.