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Ji X.,Dalhousie University | Ji X.,Hohai University | Sheng J.,Dalhousie University | Tang L.,China Institute of Water Resources and Hydropower Research | And 2 more authors.
Ocean Modelling | Year: 2011

A triply-nested coastal circulation modelling system is used in examining hydrodynamic responses of the Pearl River Estuary (PRE) and adjacent coastal waters of the South China Sea to tides, atmospheric forcing and freshwater runoff from the Pearl River during the wet season from May to August. The triply-nested coastal modelling system consists of a coarse-resolution outer model for simulating the two-dimensional tidal and wind-driven circulation over the China Seas of the northwest Pacific Ocean; an intermediate-resolution middle model for the three-dimensional (3D) simulating shelf circulation over the inner shelf of the northern South China Sea; and a fine-resolution inner model for simulating the 3D estuarine circulation over the PRE and adjacent coastal waters. Four numerical experiments are conducted by driving the triply-nested modelling system with different combinations of external forcing. Analysis of model results in the four experiments demonstrates that a large-size estuarine plume occupies the PRE during the wet season. The wet season mean circulation in the PRE is characterized by a two-layer estuarine circulation in the vertical, with a sharp salinity front near the mouth of the Estuary. In the deep waters off the PRE, the wet season mean circulation is affected by the large-scale, northeastward coastal current forced primarily by wind forcing. Model results are also used in examining the main physical processes affecting the daily and synoptic variability of circulation over the PRE and adjacent waters. © 2011 Elsevier Ltd. Source


Yu L.,Polar Research Institute of China | Zhang Z.,Polar Research Institute of China | Zhou M.,Polar Research Institute of China | Zhong S.,Michigan State University | And 4 more authors.
Advances in Atmospheric Sciences | Year: 2010

The European Center for Medium-Range Weather Forecast (ECMWF) Re-Analysis (ERA-40) and the National Centers for Environmental Prediction-National Center for Atmospheric Research (NCEP-NCAR) ECMWF (ERA-40) and NCEP-NCAR reanalysis data were compared with Antarctic station observations, including surface-layer and upper-layer atmospheric observations, on intraseasonal and interannual timescales. At the interannual timescale, atmospheric pressure at different height levels in the ERA-40 data are in better agreement with observed pressure than that in the NCEP-NCAR reanalysis data. ERA-40 reanalysis also outperforms NCEP-NCAR reanalysis in atmospheric temperature, except in the surface layer where the biases are somewhat larger. The wind velocity fields in both datasets do not agree well with surface- and upper-layer atmospheric observations. At intraseasonal timescales, both datasets capture the observed intraseasonal variability in pressure and temperature during austral winter. © 2010 Chinese National Committee for International Association of Meteorology and Atmospheric Sciences, Institute of Atmospheric Physics, Science Press and Springer-Verlag Berlin Heidelberg. Source


Ji X.,Dalhousie University | Ji X.,Hohai University | Sheng J.,Dalhousie University | Tang L.,China Institute of Water Resources and Hydropower Research | And 2 more authors.
Atmosphere - Ocean | Year: 2011

The Pearl River Estuary (PRE) on the east coast of Guangdong Province in South China is a complicated hydrodynamic system affected by various forcing functions including tides, wind forcing, and sea surface heat and freshwater fluxes. The PRE also receives a large amount of freshwater runoff from the Pearl River through eight major river inlets. In this study, the three-dimensional circulation, hydrography, and associated temporal variability in the PRE and adjacent coastal waters during the dry season from December to March are examined using a triple-nested coastal ocean circulation modelling system based on the Princeton Ocean Model. Four numerical experiments are conducted by driving the triple-nested modelling system with different combinations of external forcing functions. Analysis of multi-year model results from the four experiments demonstrates that the estuarine plume in the dry season is close to the western shore of the PRE, mainly due to the combination of the low Pearl River discharge and the influence of the southwestward coastal current over the inner shelf of the northern South China Sea. Temperature and salinity inside the estuarine plume in the dry season are weakly stratified in the vertical, with large horizontal salinity gradients near the frontal zone of the plume. Baroclinic dynamics play a very important role in the plume, with the frontal circulation forced by the combination of wind, tides and the Pearl River discharge. In the offshore deep waters of the PRE during the dry season, vertical stratification in the top 15 m is weak and circulation can be approximated by barotropic dynamics forced by wind and tides. Source


Yu L.,Nanjing University of Information Science and Technology | Zhang Z.,Polar Research Institute of China | Zhou M.,Polar Research Institute of China | Zhou M.,CAS Institute of Atmospheric Physics | And 5 more authors.
Journal of Applied Remote Sensing | Year: 2013

The trends in latent and sensible heat fluxes (LHF and SHF) over the oceans surrounding the Arctic Ocean and the contributions of the Arctic Oscillation, the Arctic dipole anomaly, the third principal component, and the Pacific-North American pattern on them are investigated using the objectively analyzed air-sea fluxes (OAFlux) dataset from 1979 to 2008. Significant positive trends in LHF appear over western and northern European coasts and the coast of the Aleutian Islands, especially in autumn. Besides in summer, autumn and winter positive trends in LHF also exist over the coast of the western North Pacific Ocean; in summer, there is also a patch of positive trends over the central North Atlantic Ocean. On the contrary, negative trends in LHF change greatly in a year. There are main negative trend centers over the Barents Sea, the coast of northeast Canada, the Bering Sea, the Sea of Okhotsk, and Hudson Bay, especially in summer and autumn. Trends in SHF are similar to those in LHF except for a small difference in area. There are significant correlations between the four indices and both LHF and SHF over these oceanic regions which result mainly from strong relationships between the sea-air-specific humidity and temperature differences and the four indices. The four indices only explain a small portion of the trends in LHF and SHF. The trends in air-sea-specific humidity and temperature differences are more closely associated with those in LHF and SHF than those in wind speed. © The Authors 2013. Source

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