The South China Sea Thermohaline Structure and Circulation

The South China Sea Thermohaline Structure and Circulation PDF

Author:

Publisher:

Published: 2002

Total Pages: 36

ISBN-13:

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In this study, the authors used the Navy's Master Oceanographic Observation Data Set (MOODS), consisting of 116,019 temperature and 9,617 salinity profiles, during 1968-1984 to investigate the temporal and spatial variabilities of South China Sea thermohaline structures and circulation. For temperature, profiles were binned into 204 monthly data sets from 1968 to 1984 (17 years). For salinity, profiles were binned into 12 climatological monthly data sets due to the data paucity. A two-scale optimal interpolation method was used to establish a three-dimensional, monthly varying gridded data set from MOODS, covering the area of 5 degrees to 25 degrees N and 105 degrees to 125 degrees E and the depth from the surface to 400 m. After the gridded data set had been established, both composite analysis and Empirical Orthogonal Function (EOF) analysis (for temperature only) were used to identify the major thermohaline features, including annual mean, monthly anomalies, and interannual thermal variabilities. The inverted monthly circulation pattern using the P-vector method also is discussed.

The South China Sea Thermohaline Structure and Circulation

The South China Sea Thermohaline Structure and Circulation PDF

Author: Binbing Ma

Publisher:

Published: 1998-09-01

Total Pages: 271

ISBN-13: 9781423557159

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The minimum curvature with spline method was used to establish a three-dimensional monthly-varying gridded data from the Navy's Master Oceanographic Observation Data Set (approximate 189,000 profiles), covering the area of 5 deg N - 25 deg N and 105 deg E - 125 deg E and from the surface to 400 m depth. For temperature, profiles were binned into 204 monthly data sets from 1968 to 1984 (17 years). Because of the paucity of salinity data, salinity profiles were binned into 12 climatological monthly data sets, and the monthly climatological mean was computed. After the gridded data set had been established, both composite analysis and the Empirical Orthogonal Function (EOF) analysis were used to identity the major thermohaline features. The first EOF mode accounts for 26.7% of the variance and represents the seasonal variation. The second EOF mode accounts for 17.7% of the variance and represents the interannual SCS warning/cooling phases. Furthermore, the P-vector method was used to invert three-dimensional velocity fields from the analyzed temperature and salinity data. Important dynamical processes, including th Kuroshio intrusion, the western boundary current (counter-current), the cross basin current (undercounter-current), the mesoscale eddies, and the basin gyre are identified.

Dynamical Mechanisms for the South China Sea Seasonal Circulation and Thermohaline Variabilities

Dynamical Mechanisms for the South China Sea Seasonal Circulation and Thermohaline Variabilities PDF

Author:

Publisher:

Published: 1999

Total Pages: 22

ISBN-13:

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The seasonal ocean circulation and the seasonal thermal structure in the South China Sea (SCS) were studied numerically using the Princeton Ocean Model (POM) with 20-km horizontal resolution and 23 sigma levels conforming to a realistic bottom topography. A 16-month control run was performed using climatological monthly mean wind stresses, restoring-type surface salt and heat, and observational oceanic inflow/outflow at the open boundaries. The seasonally averaged effects of isolated forcing terms are presented and analyzed from the following experiments: 1) nonlinear dynamic effects removed, 2) wind effects removed, and 3) open boundary inflow/outflow set to zero. This procedure allowed analysis of the contribution of individual parameters to the general hydrology and specific features of the SCS: for example, coastal jets, mesoscale topographic gyres, and countercurrents. The results show that the POM model has the capability of simulating seasonal variations of the SCS circulation and thermohaline structure. The simulated SCS surface circulation is generally anticyclonic (cyclonic) during the summer (winter) monsoon period with a strong western boundary current, a mean maximum speed of 0.5 m s21 (0.95 m s21), a mean volume transport of 5.5 Sv (10.6 Sv) (Sv [106 m3 s21), and extending to a depth of around 200 m (500 m). During summer, the western boundary current splits and partially leaves the coast; the bifurcation point is at 148N in May and shifts south to 108N in July. A mesoscale eddy on the Sunda shelf (Natuna Island eddy) was also simulated. This eddy is cyclonic (anticyclonic) with maximum swirl velocity of 0.6 m s21 at the peak of the winter (summer) monsoon. The simulated thermohaline structure for summer and winter are nearly horizontal from east to west except at the coastal regions. Coastal upwelling and downwelling are also simulated: localized lifting (descending) of the isotherms and isohalines during summer (winter) at the west boundary.

Studies of the South China Sea Circulation and Thermal Structure Using a Three Dimensional Numerical Model

Studies of the South China Sea Circulation and Thermal Structure Using a Three Dimensional Numerical Model PDF

Author: Nathan L. Edmons

Publisher:

Published: 1996

Total Pages: 122

ISBN-13:

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The seasonal ocean circulation and thermal structure in the South China Sea (SCS) were studied numerically using the Princeton Ocean Model (POM) with 20 km horizontal resolution and 23 sigma levels conforming to a realistic bottom topography. A sixteen month control run was performed using climatological monthly mean wind stresses and restoring type salt and heat fluxes as surface forcing terms and observational oceanic inflow/outflow at the open boundaries. The seasonally averaged effects of isolated forcing terms are presented and analyzed from the following experiments: 1) non-linear effects removed, 2) wind effects removed, 3) open boundary inflow/outflow set to zero, and 4) open boundary inflow/outflow doubled. This procedure allowed analysis of spatial and temporal contributions of the isolated parameter to the general hydrology of the SCS and some of its specific features. A coastal jet is identified and analyzed, as are a mesoscale topographic gyre and several counter currents. Non-linearity is shown to be important to the energy and volume transport of baroclinic eddy features, but otherwise insignificant. Boundary transport from open lateral boundaries is determined to be of considerable importance to summer circulation and thermal structure, with little effect found for the winter monsoon hydrology. In general, monsoonal circulation patterns and upwelling phenomena are determined and forced by the wind, while boundary transport effects play a secondary role in determining the magnitude of the circulation velocities.

Ocean Circulation and Air-Sea Interaction in the South China Sea

Ocean Circulation and Air-Sea Interaction in the South China Sea PDF

Author: Dongxiao Wang

Publisher: Springer Nature

Published: 2022-10-28

Total Pages: 448

ISBN-13: 9811962626

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This book summarizes achievements of the study on circulation and air–sea interaction and development of the ocean observation network in the South China Sea in the last 20 years, thus serving as a comprehensive reference book to understand the dynamic environment in the SCS. It consists of seven chapters, briefly reviewing our understanding of the SCS circulation and air–sea interaction in chapter 1, then describing in detail the upper layer circulation from large scale (SCS through flow, SCS western boundary current, etc.), to meso- and submeso-scale in Chapters 2 and 5, dilute river plume and coastal upwelling over the shelf in Chapter 3, deep ocean circulation in Chapter 4, tropical cyclone activities and air–sea flux at the interface in Chapter 6, and the construction of the observation network and database in Chapter 7. Besides the basic features of these physical processes, the book also discusses their variations and fundamental dynamics. Thus, it is written in a way that meets the different information demands from researchers working in various marine related fields.

Regional Oceanography Of The South China Sea

Regional Oceanography Of The South China Sea PDF

Author: Jianyu Hu

Publisher: World Scientific

Published: 2020-06-24

Total Pages: 500

ISBN-13: 9811206929

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This book aims to share newly obtained results and information on regional oceanography of the South China Sea by leading experts in fields such as water mass, circulation, mesoscale eddies, near-inertial motion, upwelling, mixing, continental shelf waves, internal waves and fronts. These comprehensive results can provide new insights on global and regional climate change.

Seasonal Variability of Thermohaline Front in the Central South China Sea

Seasonal Variability of Thermohaline Front in the Central South China Sea PDF

Author:

Publisher:

Published: 2003

Total Pages: 15

ISBN-13:

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An upper layer thermohaline front across the South China Sea (SCS) basin from the South Vietnamese coast (around 15 deg N) to Luzon Island (around 19 deg N) has been identified using the Navy's open domain Generalized Digital Environmental Model (GDEM) monthly mean temperature and salinity data on a O.5 deg X O.5 deg grid. This front does not occur at the surface in summer. The strength of this front is around 1 deg C/100 km at the surface and 1.4 deg C/100 km at the subsurface (50 m deep). A cross-basin current, inverted using the P-vector method is associating with the front. Meandering and eddies have been identified along this current. Seasonal and vertical variabilities of the thermohaline structure across this front are reported in this paper.

Evaluation of the Princeton Ocean Model Using South China Sea Monsoon Experiment (SCSMEX) Data

Evaluation of the Princeton Ocean Model Using South China Sea Monsoon Experiment (SCSMEX) Data PDF

Author:

Publisher:

Published: 2001

Total Pages: 20

ISBN-13:

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The Princeton Ocean Model (POM) has been implemented in the South China Sea for hindcast of circulation and thermohaline structure. A two-step technique is used to initialize POM with temperature, salinity, and velocity for 1 April 1998 and integrate it from 1 April 1998 with synoptic surface forcing for 3 months with and without data assimilation. Hydrographic and current data acquired from the South China Sea Monsoon Experiment (SCSMEX) from April through June 1998 are used to verify, and to assimilate into, POM. The mean SCSMEX data (Apr-Jun 1998) are about 0.5 deg C warmer than the mean climatological data above the 50-m depth, and slightly cooler than the mean climatological data below the 50-m depth, and are fresher than the climatological data at all depths and with the maximum bias (0.2-0.25 ppt) at 75-m depth. POM without data assimilation has the capability to predict the circulation pattern and the temperature field reasonably well, but has no capability to predict the salinity field. The model errors have Gaussian-type distribution for temperature hindcast, and non-Gaussian distribution for salinity hindcast with six to eight times more frequencies of occurrence on the negative side than on the positive side. Data assimilation enhances the model capability for ocean hindcast, if even only conductivity-temperature-depth (CTD) data are assimilated. When the model is reinitialized using the assimilated data at the end of a month (30 Apr; 31 May 1998) and the model is run for a month without data assimilation (hindcast capability test), the model errors for both temperature and salinity hindcast are greatly reduced, and they have Gaussian-type distributions for both temperature and salinity hindcast. Hence, POM gains capability in salinity hindcast when CTD data are assimilated.

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