賀伯颱風(1996)中尺度分析：第一部份：眼墻環流結構

Mesosale analysis of Typhoon Herb(1996): PartⅠ: Eyewall Structure

張保亮(Pao-Liang Chang) ； 周仲島(Ben J.-D.Jou) ； 李文兆(Wen-Chau Lee)

《大氣科學》 30卷3期 (2002/09) Pp. 201-216

摘要

本研究利用中央氣象局五分山都卜勒雷達及民用航空局中正機場都卜勒雷達觀測資料，分析賀伯颱風(1996)登陸台灣北部時，其眼牆區域環流結構的演變與特性。雷達回波顯示，賀伯颱風登陸前，颱風眼牆呈橢圓狀，颱風眼則為顯著弱回波區，颱風眼長軸約35-45km，短軸則為25-35km，並以約140-150分鐘的周期呈逆時鐘轉動。由地基速度軌跡顯示(Ground Based Velocity Track Display,GBVTD)方法分析眼牆環流顯示，眼牆區切線風場呈現波數2為主的非對稱結構，同時存在周期性的轉動現象，與眼牆回波的橢圓形分布和轉動特性一致。當賀伯颱風接近台灣東北海域時，眼牆長軸區切線風速明顯增強至70ms^(-1)，離開後則風速逐漸減弱。此階段，最大風速半徑並無明顯變動，高度2公里之最大風速半徑約35-45km，隨高度有明顯增加的現象，最大風速半徑相對於垂直方向之平均傾斜角可達40-50度，眼牆回波也存在類似的傾斜特性。颱風登陸時，波數1之非軸對稱環流結構明顯增強，大風速區位於颱風移動方向後方（東南至東北象限），強回波區也出現在颱風移動方向後方。在颱風登陸過程中，高度2公里處之最大風速半徑逐漸縮減為30km，且隨高度往外側傾斜的現象更為顯著，其最大傾斜角可達80度。

關鍵字

都卜勒雷達 ； 賀伯颱風 ； 眼墻環流結構 ； 橢圓形眼墻 ； GBVTD

並列摘要

In this study, the evolution and structure of eyewall circulation of the landfalling Typhoon Herb in1996 was documented. The elliptical eye, as revealed by the radar reflectivity, had a long axis of 35-45km and a short axis of 25-35km.The eye rotated counterclockwise with a period of 140-150 minutes. The mean tangential wind was retrieved via GBVTD method and had a structure of wave number two. The elliptical eye that revealed by the radar reflectivity had a period of the rotation same as that revealed by the wind field.
The tangential wind increased up to 70m/s as Typhoon Herb approached the northern Taiwan. Before landfall, the radius of maximum wind (RMW) at 2-km height was about 35-45km and tilted outward at about 40-50 degrees. The radar reflectivity associated with the eyewall also had similar structures. During landfall, the asymmetric structure characterized by wave number one for the tangential wind was found within regions of the maximum wind speeds. The radius of maximum winds decreased to～30km and tilted at about 80 degrees from the vertical.

並列關鍵字

Doppler radar ； Typhoon Herb ； Eyewall circulation ； Elliptical eyewall ； GBVTD