教師著作

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Start date: 2010End date: 2013

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    全球變遷對西北太平洋臺灣海域海洋生物地球化學與生態系統影響之長期觀測與研究(I)-子計畫：全球變遷因子對東海及西北太平洋黑潮海域環流與渦流變動之影響：環流數值模式
    (行政院國家科學委員會, 2013-07-31) 吳朝榮
    近年來，東海環流之研究已經有很顯著的進展，也勾勒出東海的洋流系統與其 季節性變化。最近有許多以短時間尺度擾動為主的研究，然而少有研究是針對 長時間尺度的氣候變遷因子，如聖婴現象和太平洋年代際震盪等，因而這些因 素對於環流系統的影響還不甚明瞭。東海的環流系統是生地化領域用來探索東 海的重要依據之一，如研究區域湧昇對基礎生產力的影響等，這些都必須考量 環流系統如何受氣候影響而改變，所以明瞭環流系統在不同氣候變遷因子影響 下的變動是相當重要且迫切的議題。東海環流系統主要受兩項因素主導，其一 是作用風場，季節性風向的轉換與強弱變動是季節性海流變化的成因，其二是 上游黑潮傳輸量的變化。要釐清複雜的東海環流變化，需要連續的時空序列資 料來做分析。雖然實地觀測是取得海洋環境參數最佳的方法，然而人力與設備 的有限、無法兼顧長時間與廣範圍的觀測。而衛星遙測最大的優點在於能夠大 範圍的監測整個海域，比起實地觀測更有助於研究其連續性變化。數值模式的 優點在於時間序列上是完整連續的，且空間上能完整得到不同深度的物理量。 故本研究主要以數值模擬來探討在不同氣候變遷因素影響下，東海環流及黑潮 的變異與歸因，並輔以衛星遙測與實測資料來做比對。
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    西太平洋邊緣海波浪-環流耦合數值模式之發展(I)
    (行政院國家科學委員會, 2010-07-31) 吳朝榮
    海洋包含了各種不同時空尺度、不同特性的運動型態 (海浪、潮汐、海流等)， 如何將不同運動整合於單一海洋數值模式之中，以儘量保持模擬海洋運動的完整 動力過程，是一個重要的課題。具體地來說，臺灣周邊海域冬季受到強勁東北季 風下的影響，勢必會形成洶湧的海面波浪，其強烈的攪拌作用，海氣交界面的大 量擾動，對臺灣海峽的水團混合、混合層深度、水文特性分布有何影響？在台灣 東側的黑潮在不同季節受到波浪的影響如何，是否會使得垂直混合的效果更強， 流場又如何變化？甚至一直以來都相當重要的海氣交互作用，波浪過程的加入是 否可以改善對海洋混合層熱量的模擬估算，進一步是否可以增進大氣模式的結 果，改進天氣預報或颱風預報的準確度？這些問題不僅僅需要考慮一個單純的海 流數值模式，更需要結合波浪理論與動力機制來加以研究，建立一個耦合波浪、 環流動力過程的海洋模式才得以解答上述問題。因此，本計畫的主要目的是要透 過波浪-環流耦合的技術改進現有的東亞邊緣海模式（East Asian Marginal Seas, EAMS），提升對環臺海域水文、波浪、流場模擬的能力。將新建構的東亞邊緣 海波浪-環流耦合模式將同時需要有海洋環流模式與波浪模式，海流模式部分將使 用已經建構完成且具有良好模擬結果的東亞邊緣海模式；在波浪模式方面將會使 用由中國海洋局第一海洋研究所最新發展的 MASNUM（key laboratory of MArine Science and NUmerical Modeling）波浪模式來提供波、流耦合的耦合參數。研究 的目標是以符合動力過程的方法結合波浪模式與海流模式，建立臺灣周邊海域波 流耦合模式，藉以瞭解臺灣周邊海域的物理現象、海洋環境、動力過程等。
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    西太平洋邊緣海波浪-環流耦合數值模式之發展(II)
    (行政院國家科學委員會, 2011-07-31) 吳朝榮
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    颱風整合研究---颱風過程下的大氣、波浪與洋流交互作用研究
    (行政院國家科學委員會, 2010-07-31) 吳朝榮
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    The South China Sea
    (Berlin: Springer Verlag., 2010-01-01) Liu, K.-K.; C.-M. Tseng; C.-R. Wu; I-I Lin
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    The Kuroshio and the East China Sea
    (Berlin: Springer Verlag., 2010-01-01) Liu, K.-K.; G.-C. Gong; C.-R. Wu; H.-J. Lee
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    Interannual modulation of the Pacific Decadal Oscillation (PDO) on the low-latitude western North Pacific.
    (ELSEVIER, 2013-03-01) Wu, C.-R.
    To investigate the interannual variability in the northwestern Pacific, an empirical mode decomposition (EMD) was applied to 17-year Absolute Dynamic Topography (ADT) data west of Luzon Island, the Philippines. The mean sea surface height in this area is an appropriate index for the Kuroshio intrusion into the South China Sea (SCS). Significant interannual fluctuations were extracted by the EMD. The interannual variability was strongly correlated with the Pacific Decadal Oscillation (PDO) index, but not the El Niño–Southern Oscillation (ENSO). This indicated the potential impact of the PDO on the circulation in the area. In the warm phase of the PDO (positive index), a southerly anomalous wind off the Philippines causes a northward shift of the North Equatorial Current Bifurcation Latitude (NECBL). This leads to a weakened Kuroshio off Luzon, favoring Kuroshio intrusion into the SCS. The northward migration of the NECBL also results in a weakened Kuroshio off southeast Taiwan and a larger Kuroshio transport off northeast Taiwan. The abundant westward propagating eddies impinging on the Kuroshio in the Subtropical Countercurrent region increases this transport. Although the ENSO has little effect on monsoonal winds during the warm PDO phase, it has a strong impact on the monsoon and meridional migration of the NECBL during the cold phase of the PDO. Therefore, NECBL variations only show a close correspondence with the ENSO during the cold PDO phase. Because the influence of the ENSO is not stationary, the impact of the PDO should be taken into account when examining interannual variability in the low-latitude western North Pacific.
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    Contrasting the flow patterns in the equatorial Pacific between two types of El Ni隳.
    (Taylor & Francis: STM, Behavioural Science and Public Health Titles, 2012-11-01) Wang, L.-C.; C.-R. Wu
    Outputs based on the National Centers for Environmental Prediction (NCEP) Global Ocean Data Assimilation System (GODAS) are adopted to contrast the current variations in the equatorial Pacific between two types of El Niño. The model fully resolves the equatorial currents. We found that the central Pacific El Niño (CP-El Niño) corresponds well with previous El Niño studies in that both the eastward Equatorial Undercurrent (EUC) and westward South Equatorial Current (SEC) weaken. On the other hand, the eastern Pacific El Niño (EP-El Niño) displays a distinct circulation pattern. The North Equatorial Countercurrent (NECC) strengthens in the developing phase and persists into the peak of the warm event, whereas the northern branch of the SEC (SECn) also intensifies during the mature phase and lasts for about six months. The South Equatorial Countercurrent (SECC) strengthens during the decaying phase of the EP-El Niño. The shifting of the wind stress curl associated with the thermocline variability is chiefly responsible for the unique current performance of the EP-El Niño. It is worth noting that the air–sea interaction plays an important role in the current variability not only during a CP-El Niño but also during an EP-El Niño. RÉSUMÉ [Traduit par la rédaction] Nous adoptons les sorties basées sur le système GODAS (Global Ocean Data Assimilation System) des NCEP (National Centers for Environmental Prediction) pour mettre en évidence les variations de courant dans le Pacifique équatorial entre les deux types d'El Niño. Le modèle représente complètement les courants équatoriaux. Nous trouvons que l'El Niño du centre du Pacifique (CP-El Niño) correspond bien aux études précédentes sur l'El Niño puisque le sous-courant équatorial (EUC) vers l'est et le courant sud-équatorial (SEC) vers l'ouest faiblissent. D'autre part, l'El Niño de l'est du Pacifique (EP- El Niño) affiche une configuration de circulation distincte. Le contre-courant nord-équatorial (NECC) se renforce dans la phase de développement et persiste jusqu'au maximum du réchauffement, tandis que la branche nord du SEC (SECn) s'intensifie aussi durant la phase de maturité et persiste pendant environ six mois. Le contre-courant sud-équatorial se renforce durant la phase de dissipation de l'EP-El Niño. Le changement du rotationnel de la tension du vent lié à la variabilité thermocline est principalement responsable du comportement particulier du courant de l'EP-El Niño. Il est à remarquer que l'interaction air–mer joue un rôle important dans la variabilité du courant, non seulement durant un CP-El Niño mais aussi durant un EP-El Niño.
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    Seasonal to interannual variations in the intensity and central position of the surface Kuroshio east of Taiwan
    (American Geophysical Union (AGU), 2013-09-01) Hsin Y.-C.; B. Qiu; T.-L. Chiang; C.-R. Wu
    Seasonal and interannual changes of surface Kuroshio intensity and central position east of Taiwan during 1993–2012 are investigated by quantitatively analyzing the satellite altimetry product. The Kuroshio moves inshore (offshore) off northeast of Taiwan in winter (summer), whereas it has an offshore (inshore) path off southeast of Taiwan in winter (summer). The seasonal change of heat flux over the East China Sea shelf is found to cause the seasonality of the Kuroshio central position off northeast of Taiwan, whereas the seasonal Kuroshio movement off southeast of Taiwan is found to be induced by the combined effect of the Kuroshio changes through the Luzon Strait and the eastern Luzon Island. In contrast to this y-dependent path changes, the Kuroshio becomes weaker (stronger) as a whole east of Taiwan in winter (summer). On the interannual time scales, the Kuroshio throughout the eastern coast of Taiwan intensifies and has a concurrent offshore path during the periods of 1995–1997 and 2004–2007. The relative intensity of cyclonic eddies to anticyclonic eddies off eastern Taiwan are found to contribute to these interannual Kuroshio changes.
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    Field Observations of Changes in SST, Chlorophyll and POC Flux in the Southern East China Sea Before and After the Passage of Typhoon Jangmi.
    (Chinese Geoscience Union, 2013-10-01) Shih, Y.-Y.; J.-S. Hsieh; G.-C. Gong; C.-C. Hung; W.-C. Chou; M.-A. Lee; K.-S. Chen; M.-H. Chen; C.-R. Wu
    Severe tropical storms play an important role in triggering phytoplankton blooms, yet direct field observation of evidence of the effects of a typhoon is very rare. Sea surface temperature (SST), nitrate concentration, chlorophyll a (chl a) concentration, and particulate organic carbon (POC) flux were measured before and shortly after Typhoon Jangmi which affected the southern East China Sea (SECS) on September 28 ~ 29, 2008. In situ SST (27.5 ~ 28.0°C) on September 19 ~ 21, decreased to ~24.0°C (October 3 ~ 6) in the SECS 4 ~ 7 days after the passage of Typhoon Jangmi. In situ nitrate and chl a concentrations 7-days (on October 6) after the passage of Jangmi were 1.9 μM and 1.61 mg m-3, respectively, much higher than those (nitrate: 0.3 μM and chl a: 0.73 mg m-3) concentrations before the typhoon (September 21). The enhanced chl a concentration is thus caused by a nutrient supply via vertical mixing or upwelling in the euphotic zone. The POC flux 7-days after Jangmi’s passage was 552 ± 28 mg-C m-2 d-1, a ~2.5-fold increases before the typhoon (224 ± 33 mg-C m-2 d-1, on September 21). Our results suggest that typhoons indeed can stimulate efficient POC export out of the euphotic zone, while it is still poorly understood with regard to the total effects of a typhoon on nutrient dynamics and detailed carbon sequestration due to sampling difficulty. Therefore, successional sea-going observations ought to be conducted in the affected area after the passage of typhoons.