Upper-Ocean Thermal Structure and the Western North Pacific Category 5 Typhoons. Part II: Dependence on Translation Speed
Upper-Ocean Thermal Structure and the Western North Pacific Category 5 Typhoons. Part II: Dependence on Translation Speed
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DOI：
10.1175/2009mwr2713.1
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发表时间：
2009-11-01
影响因子：
3.2
通讯作者：
Wu, Chun-Chieh
中科院分区：
文献类型：
--
作者：
Lin, I. -I.;Pun, Iam-Fei;Wu, Chun-Chieh
利用Argo浮标的新的海洋次表层观测数据，从美国气象局获得的最佳台风跟踪数据。S.联合台风警报中心，海洋混合层模式和其他支持数据集，这项工作系统地探索了平移速度，海洋次表层条件[以26摄氏度等温线（D26）和上层海洋热含量（UOHC）的深度为特征]，气旋自诱导海洋冷却负反馈，和海气焓通量对西北太平洋五级台风加强的影响。根据10年的分析，它发现，加强到5级，除了温暖的海面温度一般约29摄氏度，所需的次表层D26和UOHC在很大程度上取决于气旋的平移速度。据观察，即使在D26类似于60-70 m和UOHC类似于65-70 kJ cm（-2）的相对较浅的次表层暖层上，只要风暴能够快速移动（通常U-h类似于7-8 m s（-1）），仍然有可能有足够的焓通量将风暴加强到5级。相反，移动缓慢的台风需要更深的次表层。例如，在类似于2-3 m s（-1）的U-h处，D26和UOHC通常分别类似于115-140 m和类似于115-125 kJ cm（-2）。提出了可承受的最小翻译速度U-h_min的概念。这是一场风暴增强到5级所需的最低速度，考虑到观测到的D26和UOHC。利用3000多条Argo实测剖面资料，对D26、UOHC和U-h_min之间的关系进行了一系列数值试验，得到了明显的负线性关系，相关系数R=-0.87（-0.71）分别获得为U-h_min = -0.065 X D26 + 11.1和U-h_min = -0.05 X UOHC + 9.4。因此，这些关系可以用来作为一个指导，以预测风暴的最小速度必须以加强到5级，给定观测到的D26和UOHC。
Using new in situ ocean subsurface observations from the Argo floats, best-track typhoon data from the U. S. Joint Typhoon Warning Center, an ocean mixed layer model, and other supporting datasets, this work systematically explores the interrelationships between translation speed, the ocean's subsurface condition [characterized by the depth of the 26 degrees C isotherm (D26) and upper-ocean heat content (UOHC)], a cyclone's self-induced ocean cooling negative feedback, and air-sea enthalpy fluxes for the intensification of the western North Pacific category 5 typhoons. Based on a 10-yr analysis, it is found that for intensification to category 5, in addition to the warm sea surface temperature generally around 29 degrees C, the required subsurface D26 and UOHC depend greatly on a cyclone's translation speed. It is observed that even over a relatively shallow subsurface warm layer of D26 similar to 60-70 m and UOHC similar to 65-70 kJ cm(-2), it is still possible to have a sufficient enthalpy flux to intensify the storm to category 5, provided that the storm can be fast moving (typically U-h similar to 7-8 m s(-1)). On the contrary, a much deeper subsurface layer is needed for slow-moving typhoons. For example at U-h similar to 2-3 m s(-1), D26 and UOHC are typically similar to 115-140 m and similar to 115-125 kJ cm(-2), respectively. A new concept named the affordable minimum translation speed U-h_min is proposed. This is the minimum required speed a storm needs to travel for its intensification to category 5, given the observed D26 and UOHC. Using more than 3000 Argo in situ profiles, a series of mixed layer numerical experiments are conducted to quantify the relationship between D26, UOHC, and U-h_min. Clear negative linear relationships with correlation coefficients R=-0.87 (-0.71) are obtained as U-h_min = -0.065 X D26 + 11.1, and U-h_min = -0.05 X UOHC + 9.4, respectively. These relationships can thus be used as a guide to predict the minimum speed a storm has to travel at for intensification to category 5, given the observed D26 and UOHC.