| Summary: | 碩士 === 國立臺灣大學 === 大氣科學研究所 === 106 === Heavy rainfalls occurred over the southeastern Taiwan during 7-8 October when Typhoon Aere (2016) was located at northern South China Sea, or about 500~600 km away from Taiwan. Purpose of this study is to analyze the synoptic environment and the triggering mechanism of this heavy rainfall event.
The numerical simulation using the Advanced Research version of the Weather Research and Forecast (ARW-WRF) model is used to reproduce the heavy rainfall event in Taiwan. The synoptic analyses and the control experiment show that an anticyclone was located to the east of Taiwan, accompanied by a large-scale cyclonic circulation surrounding Typhoon Aere. Humid and strong southeasterlies due to the large-scale cyclonic circulation is observed in the southeastern Taiwan. A convergent zone, due to the northerly winds and the offshore flow caused by the blocking of the topography, was observed over where convections occurred. In the sensitivity experiments the typhoon is removed by the piecewise potential vorticity inversion (PPVI) method. The no-typhoon experiments show that the spatial distribution of convection and the heavy rainfall zone shift. However, the accumulated precipitation is as much as the control experiment because the large-scale cyclonic circulation and the anticyclone still exist. The impact of topography is also tested by the sensitivity experiment that change the altitude over Taiwan area. Results show that the spatial distribution of precipitation changes when the Taiwan topography is removed. To sum up, the heavy rainfall event is associated with synoptic-scale patterns that would have produced rainfall whether Typhoon Aere existed or not.
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