台灣地區登陸颱風降雨結構之雷達觀測

Radar Observations of Precipitation Structure of Landfall Typhoons in the Taiwan Area

周仲島(Ben Jong-Dao Jou) ； 顔建文(Chien-Wen Yen) ； 趙坤(Kun Zhao)

《大氣科學》 32卷3期 (2004/10) Pp. 183-203

摘要

中央氣象局全省都蔔勒雷達網於2001年建置完成，都蔔勒雷達所量測的降雨回波和徑向速度數據資料，提供了一個前所未有的機會，進行台灣地區降雨系統內部降雨和運動場結構的研究。本文利用位於瑞芳鄉五分山雷達回波資料探討侵台颱風降雨結構的特徵，並以納莉颱風(0116)爲例，分析颱風登陸前後降雨分佈以及降雨率變化特性。同時利用TRMM衛星降雨雷達和微波成像器資料分析納莉颱風登陸前後眼牆區深對流的發展情形。本文同時提出颱風定量降雨預報除了瞭解其降雨強度(rainfall intensity)特性外，也應該重視降雨壯度(rainfall strength)的特徵，對於侵台颱風降雨延時(duration)以及影響範圍的估計都有重大意義。

關鍵字

颱風降雨 ； 雷達回波 ； 降雨強度 ； 降雨壯度 ； 定量降雨預報

並列摘要

The Doppler weather radar network of Taiwan has been completed in 2001 by Central Weather Bureau. The reflectivity and radial velocity data collected by this network provides an unprecedented opportunity to study the precipitation structure and kinematic motion field of the mesoscale precipitation systems in the Taiwan area. In this study, the reflectivity data observed by Wu-Feng-San radar located at Re-Fang (Northern Taiwan) has been analyzed to reveal the temporal and spatial variations of rainfall structure of typhoon Nan (0116) before and after it made landfall. TRMM PR and TMI data were also used to indicate the occurrence of severe convective activity during the landfall period of Nan.
The results showed that in a weakly shear environment, the rainfall distribution of Nan while still far from landmass can be attributed to the influence of translating motion. The maximum rainfall intensity was found to locate at the right front quadrant. As the storm approached the island, possibly due to differential friction and terrain lifting, the maximum rainfall intensity shifted to the rear half of the storm. From the annular mean rainfall rate analysis, it is found the rainfall rates in the inner core (in the radius range of 100 kin) of the storm just before landfall increased more than 50% compared to that 6 hours before landfall. This result indicates that Taiwan topography plays an important role on enhancement of the rainfall just prior to the storm made landfall.
From different cases study, it has been shown that different typhoons may possess similar rainfall intensity, however, quite different rainfall strength. This difference is important to the determination of the duration and the possible affected area of the storm and should be emphasized in developing the quantitative precipitation forecasting techniques for landfall typhoons.

並列關鍵字

Typhoon rainfall ； Radar reflectivity ； Rainfall intensity ； Rainfall strength ； Quantitative precipitation forecasting