碩士 / 國防大學中正理工學院 / 應用物理研究所 / 96 / The Mei-Yu season is a major rainfall except for the typhoon season to Taiwan Island. The case study in this article is the lingering Mei-Yu frontal surface during the Mei-Yu period bringing so plenty of rainfall that it caused serious disaster and the Central Weather Bureau proclaimed extremely heavy rainfall warning lasting eighteen days in May and June, 2006. Among the was the extremely torrential rain on Ninth, June, bringing a great quantity of rainfall for middle and south Taiwan and this day’s rainfall was up to 811.5 mm at the Alishan Weather Station, which had achieved the maximum recorded number than any other weather station over the years during the Mei-Yu period and had been the fourth rainfall number in the ranking of Alishan Weather Station since its establishment.
In order to understand the WRF (Weather Research and Forecast model) model cumulus parameter’s behavior to the torrential rain incident. The research begins to test the model cumulus parameter. Betts-Miller-Janjic and New Kain-Fritsch parameter behaves well in the large scale weather system. But Betts-Miller-Janjic is excessively in predicting the rainfall. The Grell-Devenyi Ensemble is imperfect in the insufficient of the rainfall and in the handle of the whole weather system. So, follow-up study will regard New Kain-Fritsch as control group parameter.
The study case shows the vigorous moisture gathers to the sharp front of Mei-Yu by the southwest air current and Indian monsoon. The low-level jet (LLJ) offers the strong horizontal convergence. And then with the risen act on the interface of the front to strengthen the vertical speed . Enable the convection system to develop into high troposphere. At the same time, the development of mesohigh at the high level strengthens the current outflow intensity of divergence high troposphere. Cooperates with the south movement of upper-level jet (ULJ), and combines to become the branch current of ULJ. So, the low level convergence cooperating with the divergence air current at the high level strengthens the intensity and the range of the convection jointly, and impels it to develop into Mesoscale Convective System (MCS)further. It produces the benefits for the vertical sports environment to develop . The continuous generation of new convection along front maintained the long lifetime of the rainband and per persistent heavy rainfall.
In the part of testing the sea surface temperature (SST). The low level moisture will rise with the increase of SST and add the gradient of equivalent potential temperature at low level. The distribution of the rainfall also presents increasing results. Especially the SST higher area is more obvious. So, to the rainfall predictive results having the smaller model expression can have the effect on increasing the rainfall.
Eventually, Taiwan has its unique geographic surroundings. The Central Mountain stops the powerful southwest air current of Mai-Yu season in the land. Forces the underneath air current to march northward along the mountain. Meanwhile, it also strengthens the convergence intensity of territorial air current and offers the environment conditions that enhance convection. The existence of Central Mountain lowers the systemic moved speed, increases the lingering time of rain belt ,and then causes the rainfall accumulation to come into being disaster.
| Identifer | oai:union.ndltd.org:TW/096CCIT0504005 |
| Date | January 2008 |
| Creators | Wu Chi Hsiung, 吳啟雄 |
| Contributors | 廖杞昌 |
| Source Sets | National Digital Library of Theses and Dissertations in Taiwan |
| Language | zh-TW |
| Detected Language | English |
| Type | 學位論文 ; thesis |
| Format | 0 |
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