Improving Convective-Scale Quantitative Precipitation Nowcasting with the Mean Recentering scheme: A Case Study of Typhoon Morakot (2009)
碩士 === 國立中央大學 === 大氣科學學系 === 104 === In this study, the mean recentering (MRC) scheme was applied to the ensemble prediction system (EPS) and incorporated with the WRF-LETKF radar data assimilation system. The benefits of the MRC scheme to the convective-scale quantitative precipitation nowcasting (...
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ndltd-TW-104NCU050210032019-05-15T22:34:53Z http://ndltd.ncl.edu.tw/handle/86392b Improving Convective-Scale Quantitative Precipitation Nowcasting with the Mean Recentering scheme: A Case Study of Typhoon Morakot (2009) 利用系集重新定位法改善對流尺度定量降水即時預報:2009年莫拉克颱風個案研究 Pin-Ying Wu 吳品穎 碩士 國立中央大學 大氣科學學系 104 In this study, the mean recentering (MRC) scheme was applied to the ensemble prediction system (EPS) and incorporated with the WRF-LETKF radar data assimilation system. The benefits of the MRC scheme to the convective-scale quantitative precipitation nowcasting (QPN) are investigated by a case study of Typhoon Morakot (2009). As a key step in the MRC scheme, the best member was selected by the spatial correlation coefficients (SCC) of the 3-hour rainfall accumulation and the performance of the precipitation nowcasting with the EPS was evaluated. In the deterministic QPN shown in probability-matched (PM) ensemble mean, the MRC scheme reduced the unrealistic excessive rainfall at the southern Central Mountain Range (CMR). Result suggests that the effect of the MRC scheme on QPN is sensitive to the choice of the best member. Selecting the best member base on the metrics related to precipitation helps improve the patterns of the QPN and the probability quantitative precipitation forecast (PQPF). In addition, taking the mean of a few good members as the best initial condition leads to more stable improvement. The MRC scheme was further incorporated with the WRF-LETKF radar data assimilation system. First, result shows that assimilating radar radial wind helped the model to capture the strong rainfall near Alishan (阿里山). However, the unrealistic excessive rainfall prediction at southern CMR still existed. After applying the MRC scheme, the amount of hydrometeor at southern Taiwan was reduced, and thus the unrealistic excessive rainfall could be alleviated. In order to make the MRC cycle effective with the metric of rainfall accumulation, it is suggested to assimilate both radar radial velocity and reflectivity. Finally, result from the sensitivity experiments suggests that the 1-hr interval is long enough for the MRC cycle to improve the 1-6 hr QPN. Shu-Chih Yang Yu-Chieng Liou 楊舒芝 廖宇慶 2015 學位論文 ; thesis 82 zh-TW |
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碩士 === 國立中央大學 === 大氣科學學系 === 104 === In this study, the mean recentering (MRC) scheme was applied to the ensemble prediction system (EPS) and incorporated with the WRF-LETKF radar data assimilation system. The benefits of the MRC scheme to the convective-scale quantitative precipitation nowcasting (QPN) are investigated by a case study of Typhoon Morakot (2009).
As a key step in the MRC scheme, the best member was selected by the spatial correlation coefficients (SCC) of the 3-hour rainfall accumulation and the performance of the precipitation nowcasting with the EPS was evaluated. In the deterministic QPN shown in probability-matched (PM) ensemble mean, the MRC scheme reduced the unrealistic excessive rainfall at the southern Central Mountain Range (CMR). Result suggests that the effect of the MRC scheme on QPN is sensitive to the choice of the best member. Selecting the best member base on the metrics related to precipitation helps improve the patterns of the QPN and the probability quantitative precipitation forecast (PQPF). In addition, taking the mean of a few good members as the best initial condition leads to more stable improvement.
The MRC scheme was further incorporated with the WRF-LETKF radar data assimilation system. First, result shows that assimilating radar radial wind helped the model to capture the strong rainfall near Alishan (阿里山). However, the unrealistic excessive rainfall prediction at southern CMR still existed. After applying the MRC scheme, the amount of hydrometeor at southern Taiwan was reduced, and thus the unrealistic excessive rainfall could be alleviated. In order to make the MRC cycle effective with the metric of rainfall accumulation, it is suggested to assimilate both radar radial velocity and reflectivity. Finally, result from the sensitivity experiments suggests that the 1-hr interval is long enough for the MRC cycle to improve the 1-6 hr QPN.
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author2 |
Shu-Chih Yang |
author_facet |
Shu-Chih Yang Pin-Ying Wu 吳品穎 |
author |
Pin-Ying Wu 吳品穎 |
spellingShingle |
Pin-Ying Wu 吳品穎 Improving Convective-Scale Quantitative Precipitation Nowcasting with the Mean Recentering scheme: A Case Study of Typhoon Morakot (2009) |
author_sort |
Pin-Ying Wu |
title |
Improving Convective-Scale Quantitative Precipitation Nowcasting with the Mean Recentering scheme: A Case Study of Typhoon Morakot (2009) |
title_short |
Improving Convective-Scale Quantitative Precipitation Nowcasting with the Mean Recentering scheme: A Case Study of Typhoon Morakot (2009) |
title_full |
Improving Convective-Scale Quantitative Precipitation Nowcasting with the Mean Recentering scheme: A Case Study of Typhoon Morakot (2009) |
title_fullStr |
Improving Convective-Scale Quantitative Precipitation Nowcasting with the Mean Recentering scheme: A Case Study of Typhoon Morakot (2009) |
title_full_unstemmed |
Improving Convective-Scale Quantitative Precipitation Nowcasting with the Mean Recentering scheme: A Case Study of Typhoon Morakot (2009) |
title_sort |
improving convective-scale quantitative precipitation nowcasting with the mean recentering scheme: a case study of typhoon morakot (2009) |
publishDate |
2015 |
url |
http://ndltd.ncl.edu.tw/handle/86392b |
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