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題 名 | 奇異向量在全球波譜淺水模式颱風路徑系集預報的應用=The Application of Singular Vectors in the Typhoon Track Ensemble Prediction of the Global Shallow Water Spectral Model |
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作 者 | 賴永鑫; 曾建翰; 陳建河; | 書刊名 | 大氣科學 |
卷 期 | 42:2 2014.09[民103.09] |
頁 次 | 頁113-128 |
分類號 | 328.888 |
關鍵詞 | 奇異向量; 最佳路徑; 適應性觀測; 投落送; Singular vectors; The best track; Adapting observation; Dropwindsound; |
語 文 | 中文(Chinese) |
中文摘要 | 淺水模式應用於颱風路徑的系集預報仍有其價值,理由為計算花費成本簡單,可作為參照的最低標準。本研究所採用的淺水模式為配合氣象局全球波譜模式的淺水模式,沒有邊界條件問題,方程組承繼全球模式,除可做動力學研究外,同時作為測試平台供以後全球模式使用。奇異向量(singular vectors,簡稱SVs)的應用為歐洲中心所採行的系集預報方法之一,精神為求算大氣基本場的最不穩定初始擾度場作為系集成員,在改動初始場儘可能少的情形下(通常僅改動2~3%)於一定時間內求得最大合理分歧的一組預報。中央氣象局的奇異向量系統架構於T42L40簡化版的全球波譜模式上,內含簡單的邊界層及簡單物理過程。從T42L40所計算的奇異向量,可於垂直上擷取不同層的平均值給予淺水模式使用。本研究使用全球範圍的單層淺水模式,把SVs視為模式初始場的最佳擾動分布來進行莫拉克颱風及凡那比颱風的系集路徑預報,而且在模擬過程中把SVs當作一種強制項的作用,每6小時加入SVs至淺水模式中直到24小時為止。二個個案的預報結果顯示,加入SVs成功將原始的單一路徑散開,而且凡那比颱風的系集預報範圍有包含到最佳路徑(best track)的方向。同時,為驗證SVs的空間分佈有重要意義,實驗測試將SVs平移出原先的區域,所得到的系集預報發散度皆不如原本的模擬結果,表示本研究所計算的SVs的空間分布作為影響颱風路徑預報的敏感區域有一定的可信度。本研究的實驗測試過程可為未來全球模式的颱風路徑系集預報所用,同時SVs計算的敏感區可作為資料同化工作中的適應性觀測(adapting observation)如投落送(dropwindsound)等工作利用,加強區域局部觀測。 |
英文摘要 | The typhoon track ensemble prediction of the shallow water model is still beneficial in operation because the cost is economic and the result could be the minimal criterion of forecast accuracy. In this study, we adopt the global shallow water spectral model which is simplified from the global spectral model of Central Weather Bureau, Taiwan, that is, this shallow water model does not need to deal with horizontal boundary and the equations are consistent with the global spectral model. This global shallow water spectral model can be not only used in basic dynamic researches but the testing platform of the global forecast system. The singular vector method is one of the procedures of ensemble prediction system in European Centre for Medium-Range Weather Forecasts. The spirit of the singular vectors is to get the basic flow initial most unstable perturbations which modify the basic flow least (around %2-%3) and get the most divergent evolution in the specific period of time after. The singular vectors of Central Weather Bureau are calculated from T42L40 simplified global spectral model with simple boundary layer process and simple physical scheme. The singular vectors through vertical interpolation can be taken several specific vertical layers average as the perturbations in the shallow water model. The typhoon Morakot and Fanapi was chosen for this study. The singular vectors are regarded as the initial perturbations and the forcings in every 6 hours within the beginning 24 hours time integration. In these two cases, the singular vector ensemble predictions successfully spread the typhoon tracks, and the ensemble set of Fanapi can cover the typhoon best track. Moreover, the different space positions of singular vectors are tested. The singular vector space areas are the most sensitive perturbation positions, so when we move the singular vectors out of their original areas, the track divergences are fewer than the original areas track spreads. That means somehow the singular vectors pointing the sensitive areas that we should pay more attention for typhoon track ensemble prediction. The results of this study can be extended to global ensemble prediction system. At the same time, the singular vectors sensitive area information points out which local area observations should be enhanced or be worth improved. It can be auxiliary help for the adaptive observations like the typhoon dropsound experiment in data assimilation work. |
本系統中英文摘要資訊取自各篇刊載內容。