臺灣地形與颱風環流之分析研究

曲克恭

A Diagnostic Study of Typhoon Circulation Affected by Taiwan Island

Abstract

1. 1366 surface wind field maps of 53 typhoons which have affected Taiwan from 1952 to 1975 and some of the rawinsonde data from 1955 to 1975 were analysed in order to study the horizontal and vertical characteristics of the topographical affected typhoon wind field.
2. Typhoon circulation was affected significantly by the special feature of Taiwan Island. The main result of this study is knowing the separation vortex and local terrain vortex and the Typhoon Jet named by this study also were discovered and some of its patterns were preliminarily analysed.
3. Different pattern of wind field over Taiwan and Taiwan Strait will be associated with different location and strength of typhoon in the vicinity of Taiwan or the center of typhoon has landed over Taiwan. Based on the stream line maps of 58 individual typhoons composition stream line maps were made and the related occurance frequency of separation vortex also computed.
4. Local topographical vortex is a special phenomenon near Yilan and Tawu and most of the separation vortices were found in the west side and north of the Central Mountain Range. Much less of the separation vortices in east side of the mountain may be due to the terrain feature and lack of data in that area.
5. From the vertical profiles of wind of Taoyuan, Makung and Tungkang significant strong wind layers were found and good indications are both on the horizontal and time cross-section charts. So we name it as “Typhoon Jet.” Its height varies considerably from about 300m to 20,000m in low level and from 40,000m to 50,000m in middle level. Sometimes the strong vertical wind shear of it is about two orders larger than the horizontal wind shear of the strong typhoons. The rolling current may be formed near the Jet and causes different rainfall distribution over Taiwan.