台灣低壓的數值模擬

Numerical Study of a Taiwan Low

許武榮(Wu-Ron Hsu) ； 黃麗玫(Li-Mei Huang)

《大氣科學》 19卷2期 (1991/06) Pp. 131-147

摘要

本文以數值模式為工具探討了台灣低壓早期的形成與發展，在初始場設定一典型之大陸性冷氣團出海之天氣型態，而水平方向完全沒有擾動的情形下，台灣低壓自然地發生了。模擬低壓之地理位置與觀測台灣低壓經常發生的位置相吻合。分析結果顯示台灣低壓的壓力擾動僅2mb，發展的深度約4公里，這些結果與過去分析－台灣低壓個案垂直結構的結果頗為一致。由敏感度分析顯示，地形阻擋效應使台灣東北方海域熱通量增強，導致台灣低壓發生。海溫的分佈與冷氣團強度同為重要的激發機制，特別是水汽通量大小對於海溫的變化極其敏感，而水汽的多寡決定了層雲發展的深度，對低壓的成長有正面的貢獻。

關鍵字

台灣低壓 ； 黑潮 ； 對流邊界層

並列摘要

A Numerical model was used to study the development of a Taiwan low in its early stage of life cycle. A typical winter-time weather system of cold air outbreak is imposed as an initial condition. The model reproduces a Taiwan low without any initial perturbations. The location of the simulated low pressure system matches with the typical area where Taiwan lows are usually occured. The results show that it is a system with pressure perturbation of only 2mb, and a depth of only 4km. These characteristics are quite consistent with a case study of the phenomenon by Saito. Sensitivity tests show that the three main factors contributing to the formation of the low pressure system are: 1. the blocking effect of the Cental Mountain Range which increases surface heat fluxes in the area to the northeast of Taiwan; 2. the warm ocean; and 3. the cold air mass. The surface moisture flux, which is very sensitive to the change of the sea surface temperature, is particularly important in the formation of a deep convective boundary layer where Taiwan low is embedded in.

並列關鍵字

Taiwan low ； Kuroshio ； convective boundary layer