登陆台风的能量学分析

AN ENERGETIC ANALYSIS OF A LANDED TYPHOON

中文摘要:

      本文对一个登陆我国的台风以及它与西风带相互作用的过程进行了能量学分析。计算了动能平衡和有效位能。结果表明:(1)台风在登陆后的减弱过程中,与环境大气的动能交换较小,可以把这个台风看作是一个动能的“准封闭系统”。(2)在登陆台风减弱过程的不同阶段,热力和动力作用很不相同。刚登陆时,伴随着大暴雨,积云对流群是台风的重要动能源。对流层上部穿越等压线的运动是台风减弱的重要原因。其中以正压过程为主。台风与西风带系统相互作用后的动能平衡与温带气旋类似。斜压过程的动能产生率增加,摩擦在台风衰减过程中起重要作用。(3)在台风附近有大量的有效位能释放。通过台风系统的边界有大量位能注入环境大气。而在台风倒槽里新生的气旋,则从环境大气中得到位能。这种过程可能是台风与周围环境相互作用的一种主要方式。

英文摘要:

      The case selected in this study is an intense typhoon (Billie) which moved over the Southeast China and interacted with an extratropical frontal system. Kinetic energy(KE) budget and available potential energy (APE) were computed by using the quasi-Lagrangian scheme during the period 10 to 12 Aug. 1976. The main results of this study are: 1)In the weakening process of the landed typhoon, exchange of KE with the environment was small. Then the typhoon could be considered as a "quasi-closed" system. 2) In the various weakening stages of the landed typhoon, the thermodynamic and dynamic processes were different. When the typhoon moved just over land and accompanied with heavy rain, the latent heat and moist convection were still the major source of KE. The energy sink due to cross-contour flow in the upper troposphere was the important reason for the decrepitude of the typhoon. The barotropic process was dominant in the decrease of KE. However, after the typhoon interacted with the westerlies, the KE generation by baroclinic process increased and the frictional dissipation played a significant role in this stage. 3) Throughout the period of interest, large amount of APE entered into the environmental atmosphere through the lateral boundaries of the typhoon circulation. This may be one of the major processes of interaction between the typhoon and the surroundings.