教師著作

Permanent URI for this collectionhttp://rportal.lib.ntnu.edu.tw/handle/20.500.12235/37078

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Author: search.filters.author.C.-R. Wu

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Now showing 1 - 10 of 26
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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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    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.
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    Variability analysis of Kuroshio intrusion through Luzon Strait using growing hierarchical self-organizing map
    (Springer-Verlag, 2012-08-01) Tsui, I.-F.; C.-R. Wu
    An advanced artificial neural network classification algorithm is applied to 18 years of gridded mean geostrophic velocity multi-satellite data to study the Kuroshio intrusion into the South China Sea through the Luzon Strait. The results suggest that the Kuroshio intrusion may occur year round. However, intrusion is not the major characteristic of the region. The intrusion mode occurs only 25.8 % of the time. Winter intrusion events are more frequent than summer events. Both stronger intrusion (which is related to wind speed) and weaker intrusion (which may be related to the upstream Kuroshio transport) may occur during winter, but stronger intrusion is dominant. In summer, the Kuroshio intrusion is almost the weaker type. The Kuroshio intrusion through the Luzon Strait usually occurs when the Pacific decadal oscillation index is positive (72.1 % of the time). This study shows that growing hierarchical self-organizing map is a useful tool for analyzing Kuroshio intrusion through the Luzon Strait.
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    Mindanao Current/Undercurrent in an Eddy-Resolving GCM
    (American Geophysical Union (AGU), 2012-06-01) Qu T.; T.-L. Chiang; C.-R. Wu; P. Dutrieux; D. Hu
    Analysis of results from an eddy-resolving general circulation model showed two subsurface velocity cores in the mean within the depth range between 400 and 1000 m below the Mindanao Current (MC). One is confined to the inshore edge at about 126.8°E and connected with the Sulawesi Sea. The other takes place somewhat offshore around 127.7°E, being closely related to the intrusion of South Pacific water. Both cores are referred to as the Mindanao Undercurrent (MUC). The MC/MUC is approximately a geostrophic flow, except on the inshore edge of the MUC where up to 50% of the mean flow can be explained by ageostrophic dynamics. In contrast with the well-defined southward flowing MC, the MUC is of high velocity variance relative to the mean. Empirical orthogonal function (EOF) analysis shows that approximately 60% of the total velocity variance is associated with two meandering modes, with their major signatures in the subthermocline. The dominant time scale of variability is 50–100 days. An ensemble of these meso-scale fluctuations provides a northward freshwater flux on the offshore edge of the Philippine coast, which to a certain extent explains why water of South Pacific origin appears to extend farther northward than the mean MUC. In the offshore velocity core of the MUC, for example, eddy induced freshwater flux is equivalent to a mean flow of about 0.3 m s−1 in the density range between 26.9 and 27.3 kg m−3, which is greater than the mean current by a factor of 6.
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    An updated examination of the Luzon Strait transport.
    (American Geophysical Union (AGU), 2012-03-01) Hsin, Y.-C.; C.-R. Wu; S.-Y. Chao
    Despite numerous previous estimates of Luzon Strait transport (LST), we attempt an update using a fine-resolution model. With these improvements, the circulation in and around Luzon Strait shows up rather realistically. Intrusion of a Kuroshio meander into the South China Sea (SCS) is seasonally varying. The LST, especially in the upper ocean, caused by a small difference between the large meander inflow and outflow, is also seasonally varying and subject to large standard deviation. The annual mean LST is estimated to be westward (−4.0 ± 5.1 Sv) along 120.75°E. We have also conducted process of elimination experiments to assess the relative importance of open ocean inflow/outflow, wind stress, and surface heat flux in regulating LST and its seasonality. The East Asian monsoon winds stand out as the predominant forcing. Without it, the upper ocean LST changes from westward to eastward (ranging up to 4 Sv) and, with misaligned seasonality, triggering an inflow from the Mindoro Strait to the SCS to replenish the water mass loss. Discounting monsoon winds, sea level in the Sulu Sea is generally higher because it receives the Indonesian Throughflow before the SCS, which causes an inflow from the Sulu Sea to the SCS. On the other hand, the annual mean wind from the northeast invites outflow from the SCS to the Sulu Sea (or inflow from the Luzon Strait). Weighing the two competing factors together, we see the cessation of northeast monsoon as a condition favorable for the Luzon Strait outflow or the Mindoro Strait inflow.
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    Editorial - International Workshop on Modeling the Ocean (IWMO) special issue part 2 in Ocean Dynamics
    (Springer-Verlag, 2010-10-01) Oey, L.-Y.; T. Ezer; Y. Miyazawa; C.-R. Wu