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| Autor: | Wen-Jou Chen, 陳文柔 |
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| Rok vydání: | 2017 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 105 Rapid-Intensification (RI) typhoon forecast remains a critical challenge, it usually causes severe damage all at once. According to the previous research, a critical mechanism for reducing rapid-intensifying typhoons was “the positive feedback” occurred in or near the eyewall region. That is, for low-level convergence enhances upward flow motion, latent heat then releases to surroundings causing a warm-core in mid-upper-level. Warm-core structure helps to maintain typhoon intensity; then divergence in upper level pulls lower flow to transport updraft at the same time, and it finally forms second circulation that intensifies typhoons. In this study, we conducted a 48-hour data assimilation and a 72-hour forecast experiment by using GSI 3D-Var v3.3 data assimilation system and WRF model 3.6.1 version. An rapid-intensifying typhoon Megi(2010) was chosen to analyze the RI processes from two sets of experiments, i.e., from the assimilation of GTS only and GTS with RO data. These two experiments will used to evaluate two different atmospheric states in the initial fields and followed typhoon forecasts in the RI stages. Some important RI mechanisms were analyzed, such as convergence, vertical velocity, wind shear, 700 hPa relative humidity and temperature anomaly. GTS+RO experiment gave positive impact to the typhoon simulation. Sensitivity tests show that RO profiles below 500hPa played an important role in the improvement of intensity; Moreover, assimilating lower number of RO profiles will degrade the forecast performance but not in linear relationship with the used RO data. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
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