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31.
Beta spiral technique can be used to determine the three dimensional velocity field, usually in the open ocean, as functions of depth at a single location. This work is aimed at applying the method to the lower layers in the western boundary area of the Pacific at two locations covered by 5 CTD stations each and then using the results to study the vertical structure of the western boundary current in the Pacific. Contribution No. 1776 from the Institute of Oceanology, Academia Sinica. This work is supported by NSFC (No. 4880230).  相似文献   
32.
Based on the temperature data along 34°N, 35°N and 36°N sections in August from 1977 to 2003, the structure and formation of the Southern Yellow Sea Cold Water Mass (SYSCWM) and its responses to El Nino events are analyzed. Results show that: (1) There exist double cold cores under the main thermocline along the 35°N and 36°N sections. Also, double warm cores exist above the main thermocline along the 36°N section. (2) Thermocline dome by upwelling separates the upper warm water into two parts, the eastern and western warm waters. Additionally, the circulation structure caused by upwelling along the cold front and northeastward current along the coast in summer is the main reasons of double warm cores along the 36°N section. The intermediate cold water is formed in early spring and moves eastward slowly, which results in the formation of the western one of double cold cores. (3) Position of the thermocline dome and its intensity vary interannually, which is related to El Nino events. However, the  相似文献   
33.
Seasonal variability of the North Equatorial Current (NEC) transport in the western Pacific Ocean is investigated with ECMWF Ocean Analysis/Reanalysis System 3 (eRA-S3). The result shows that NEC transport (NT) across different longitudes in the research area shows a similar double-peak structure, with two maxima (in summer and winter), and two minima (in spring and autumn). This kind of structure can also be found in NEC geostrophic transport (NGT), but in a different magnitude and phase. These differences are attributable to Ekman transport induced by the local meridional wind and transport caused by nonzero velocity at the reference level, which is assumed to be zero in the NGT calculation. In the present work, a linear vorticity equation governing a 1.5-layer reduced gravity model is adopted to examine the dynamics of the seasonal variability of NGT. It is found that the annual cycle of NGT is mainly controlled by Ekman pumping induced by local wind, and westward-propagating Rossby waves induced by remote wind. Further research demonstrates that the maximum in winter and minimum in spring are mostly attributed to wind east of the dateline, whilst the maximum in summer and minimum in autumn are largely attributed to that west of the dateline.  相似文献   
34.
Decadal variations of the transport and bifurcation latitude of the North Equatorial Current (NEC) in the northwestern tropical Pacific Ocean over 1959–2011 are investigated using outputs of the Ocean Analysis/Reanalysis System 3 prepared by the European Centre for Medium-Range Weather Forecasts. The results indicate that the NEC transports at different longitudes have different decadal fluctuations, which are strongest around 139°E. The NEC bifurcation latitude (NBL) has its largest decadal variations around 150 m. Extremes of the decadal NEC transport and NBL before 1975 correspond to different circulation anomalies from those after 1975. The regression map against decadal NBL exhibits negative sea surface height (SSH) anomalies and a cyclonic gyre anomaly over the northwestern tropical Pacific Ocean, while that against the decadal NEC transport exhibits a dipole structure, with positive/negative SSH anomalies to the north/south of about 13°N. Furthermore, decadal variations of the NEC transport and NBL over the whole period have different correlations with Pacific Decadal Oscillation (PDO) and Tropical Pacific Decadal Variability (TPDV). Generally, the decadal NEC transport shows higher correlations with PDO than with TPDV, while the NBL has higher correlations with TPDV than with PDO. The high correlation of decadal NEC transport with PDO mainly comes from that of its northern branch with PDO, while its southern branch shows higher correlation with TPDV.  相似文献   
35.
Heat center of the western Pacific warm pool   总被引:1,自引:0,他引:1  
A heat center (HC) of the western Pacific warm pool (WPWP) is defined, its variability is examined, and a possible mechanism is discussed. Analysis and calculation of a temperature dataset from 1945-2006 show that the mean position of the HC during this period was near 0.4°S/169.0°E, at 38.0 m depth. From a time series of the HC, remarkable seasonal variability was found, mainly in the meridional and vertical directions. Interannual variabilities were dominant in the zonal and vertical directions. In addition, semiannual variation in the HC depth was discovered. The longitude of the HC varies with ENSO events, and its latitude is weakly related to ENSO on time scales shorter than a decade. The variation of the HC longitude leads the Nio-3 index by about 3-4 months, and its depth lags the index for approximately 3 months. It is concluded that the HC depth results from a combination of its longitudinal and latitudinal variations. Low-pass-filtered time series reveal that the HC has moved eastward since the mid 1980s.  相似文献   
36.
The global surface temperature change since the mid-19th century has caused general concern and intensive study. However, long-term changes in the marginal seas, including the seas east of China, are not well understood because long-term observations are sparse and, even when they exist, they are over limited areas. Preliminary results on the long-term variability of sea surface temperature (SST) in summer and winter in the seas east of China during the period of 1957-2001 are reported using the Ocean Science Database of Institute of Oceanology, Chinese Academy of Sciences, the coastal hydrological station in situ and satellite data. The results show well-defined warming trends in the study area. However warming and cooling trends vary from decade to decade, with steady and rapid warming trends after the 1980s and complicated spatial patterns. The distribution of SST variation is intricate and more blurred in the areas far away from the Kuroshio system. Both historical and satellite data sets show significant warming trends after 1985. The warming trends are larger and spread to wider areas in winter than in summer, which means decrease in the seasonal cycle of SST probably linked with recently observed increase of the tropical zooplankton species in the region. Spatial structures of the SST trends are roughly consistent with the circulation pattern especially in winter when the meridional SST gradients are larger, suggesting that a horizontal advection may play an important role in the long-term SST variability in winter.  相似文献   
37.
The low-frequency atmosphere-ocean coupled variability of the southern Indian Ocean(SIO) was investigated using observation data over 1958-2010.These data were obtained from ECMWF for sea level pressure(SLP) and wind,from NCEP/NCAR for heat fluxes,and from the Hadley Center for SST.To obtain the coupled air-sea variability,we performed SVD analyses on SST and SLP.The primary coupled mode represents 43% of the total square covariance and is featured by weak westerly winds along 45-30 S.This weakened subtropical anticyclone forces fluctuations in a well-known subtropical dipole structure in the SST via wind-induced processes.The SST changes in response to atmosphere forcing and is predictable with a lead-time of 1-2 months.Atmosphere-ocean coupling of this mode is strongest during the austral summer.Its principle component is characterized by mixed interannual and interdecadal fluctuations.There is a strong relationship between the first mode and Antarctic Oscillation(AAO).The AAO can influence the coupled processes in the SIO by modulating the subtropical high.The second mode,accounting for 30% of the total square covariance,represents a 25-year period interdecadal oscillation in the strength of the subtropical anticyclone that is accompanied by fluctuations of a monopole structure in the SST along the 35-25 S band.It is caused by subsidence of the atmosphere.The present study also shows that physical processes of both local thermodynamic and ocean circulation in the SIO have a crucial role in the formation of the atmosphere-ocean covariability.  相似文献   
38.
于乐江  胡敦欣  冯俊乔 《大气科学》2011,35(6):1091-1104
利用1951~1998年多种大气和海洋资料,研究了太平洋和印度洋在南海夏季风爆发中的作用.结果表明,影响南海夏季风爆发早晚的因素存在着年代际变化:1951~1970年,印度洋起主要作用;1970~1998年西太平洋起主要作用.该年代际变化主要是1970年前后北极涛动(AO)的跃变以及西太平洋副高强度变化的结果.1951...  相似文献   
39.
Yuan  Xin  Wang  Qingye  Feng  Junqiao  Hu  Dunxin 《中国海洋湖沼学报》2021,39(6):2127-2143
Journal of Oceanology and Limnology - Traditionally, the estimated volume transport of the North Equatorial Current/Undercurrent (NEC/NEUC) is based on geostrophic equations and/or model results;...  相似文献   
40.
Seasonality and causes of the Yellow Sea Warm Current   总被引:1,自引:0,他引:1  
To study the seasonality and causes of the Yellow Sea Warm Current (YSWC) in detail, rotated empirical orthogonal function (REOF) and extended associate pattern analysis are adopted with daily sea surface salinity (SSS), sea surface temperature (SST) and sea surface height (SSH) datasets covering 1126 days from American Navy Experimental Real-Time East Asian Seas Ocean Nowcast System in the present paper. Results show that in the Yellow and East China Seas, the YSWC is a mean barotropic flow as compensation of winter-monsoon-driven surface currents, which has been directly observed. When East Asia winter monsoon weakens, so do the meridional pressure gradient of the surface seawater and the YSWC, while the transversal pressure gradient changes rather slowly that results in the YSWC left turning. In addition, there is southward mean flow compensation of summer-monsoon-driven surface currents, which actually was also directly ob-served.  相似文献   
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