西北太平洋地區颱風發展過程之分析

An Analysis of Typhoon Development in Western North Pacific

李清勝(Cheng-Shang Lee) ； 呂國臣(Kuo-Chern Lu)

《大氣科學》 18卷3期 (1990/09) Pp. 193-212

摘要

本研究利用資料診斷分析，探討西北太平洋地區颱風（最大風速大於60 Kt）強度變化時的結構和環流特徵，以幫助瞭解導致颱風強度增加的物理過程。在分析時，除了採用美國科州州大的颱風合成分析法，分析兩組合成颱風資料外，同時利用FGGE資料，探討1979年兩個颱風個案於強度變化時之外圍環流特徵。合成分析結果顯示，加強型颱風較非加強型颱風具有較強的高層外流和低層内流，強内／外流區之徑向範圍亦較大且連續。半徑4°以内，加強型颱風具有較強之平均上升運動、積雲加熱效應（Q1）、降水和水平水汽輻合。非加強型颱風則於中心附近具有較暖的中、高對流層，導致其梯度熱力風平衡關係之剩餘項在550～200 mb皆為負值（或垂直風切相對較弱，不足以平衡相對較強的徑向溫度梯度），加強型颱風則剩餘項大多為正值，此梯度熱力風平衡上的差異，有待進一步研究其角色。合成分析亦發現颱風於加強過程中，可能因高層有較強外流，導致400 mb左右出現補償性内流；然而此特徵在個案分析中並不顯著。至於伴隨加強型颱風出現之較強高層外流，在個案中則以高層外流噴流的型式出現；Hope颱風（1979）之高層強外流，乃受TUTT之影響，而Owen颱風（1979）之外流層特徵則和合成颱風非常類似。

關鍵字

颱風 ； 颱風強度變化

並列摘要

The purpose of this research is to study the physical processes which can lead to typhoon intensification in the Western North Pacific. The characteristics of structures and circulation patterns associated with those intensifying typhoons (maximum wind exceeds 60 knots) are analyed. The analyses utilize the rawinsonde composite technique developed at Colorado State University to study both the intensifying and the non-intensifying typhoons. In addition, the surrounding circulation patterns associated with two intensifying typhoons in 1979 are discussed using FGGE data.Results of composite analysis show that the intensifying typhoon has stronger upper level outflow and low level inflow than the non-intensifying typhoon. The radial extent of strong inflow/outflow region is greater and more continuous for the intensifying typhoon. Inside 4° radius, the mean upward motion, the cumulus heating (Q1), the precipitation and the horizontal moisture convergence are also stronger for the intensifying typhoon. The non-intensifying typhoon however, posses warmer mid-upper troposphere. In consequence, the residual term in the gradient thermal wind equation is negative at 550-200 mb. In other words, the vertical wind shear can not balance the relatively stronger radial temperature gradient. The residual term of the intensifying typhoon is positive almost through the whole troposphere. The role of wind-mass balance in typhoon intensification process deserves further study.The composite analysis also reveals that a compensating inflow occurs around 400 mb after typhoon intensification, probably due to the stronger upper level outflow associated with the intensifying typhoon. However, this compensating inflow is not apparent in the individual case analysis. As to the upper level outflow feature, two individual intensifying typhoons show a pattern of strong upper level outflow jet instead of the strong mean outflow. The strong outflow of Typhoon II (1979) is associated with the existence of a TUTT system. The upper level flow pattern of Typhoon Owen (1979), however, is very similar to that of the composite intensifying typhoon.

並列關鍵字

typhoon ； typhoon intensity change