登陆热带气旋海马（0421）变性加强的诊断研究

Diagnosis of the extra-tropical transition of landfalling Tropical Cyclone Haima(2004)

中文关键词:  热带气旋海马，变性，辐散风，动能方程

英文关键词:Tropical Cyclone Haima, Extra-tropical transition, Divergent wind, Kinetic energy equation

中文摘要:

      利用台风年鉴、NCEP/NCAR再分析资料、旋转风及辐散风动能诊断方程对热带气旋海马（2004）的变性加强过程进行了诊断分析。结果表明，海马变性加强发生在向极运动过程中，与高空槽前急流发生耦合，西风槽引导冷空气侵入海马环流内部，形成半冷半热结构。进一步利用辐散风动能方程诊断分析发现，海马变性加强的主要能量来源有两个，一个是西风槽带来的冷空气下沉侵入低压环流释放的有效位能，另一个是海马与环境系统发生相互作用导致其低压环流不均匀分布的总动能通过辐散风向低压动能的转化。二者的值为同一量级。此外，此两种能量来源均可使海马低层平均风速在6 h增加10 m/s以上，地面摩擦和大气内摩擦是TC动能消耗的主要原因，而动能垂直通量的散度项使得动能由低层输送至高层。

英文摘要:

      Based on the tropical cyclone yearbooks, the NCEP/NCAR reanalysis data and the kinetic energy equation of rotational and divergent wind, study is carried out of the extra tropical transition and reintensifying of the landfalling Tropical Cyclone Haima(2004). The results show that, when moving toward the north pole, Haima couples with the jet before the upper westerly trough, which induces cold air to invade the circulation of Haima. Furthermore, the divergent wind kinetic energy equation is applied to diagnose the kinetic energy sources of the extra tropical transition of Haima. It is found that, one of them is from the released available potential energy by cold air’s invading the tropical cyclone circulation, and the other is the transformation from the total kinetic energy of uneven distribution in the circulation to the tropical cyclone kinetic energy via the divergent wind due to the interaction between Haima and the peripheral synoptic systems. Both are in the same magnitude, and able to enforce the low level wind of Haima increase up to 10 m/s within 6 h. The consumption of kinetic energy of the tropical cyclone is due to the land surface friction and atmosphere internal friction, and the divergence term of vertical kinetic energy flux causes the divergent wind kinetic energy to transport from low levels to upper levels.