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Li J.,PLA University of Science and Technology | Li J.,State Oceanic Administration | Zhang R.,PLA University of Science and Technology | Jin B.,Beijing Applied Institute of Meteorology
Ocean Science | Year: 2011

Cyclonic and anticyclonic eddies from large scale to submesoscale in the northern South China Sea (NSCS) have been statistically characterized based on the satellite-tracked Lagrangian drifters using our developed geometric eddy identification method. There are in total 2208 eddies identified, 70% of which are anticyclonic eddies. If the submesoscale eddies are eliminated, the other eddies in the NSCS will show a 1.2:1 ratio of the number of anticyclones (210) to the number of cyclones (171). The spatial distribution of the eddies is regional: in southwest of Taiwan, the number of anticyclones dominates the number of cyclones, and most of them are the submesoscale anticyclones with small radii; in contrast, the large and medium cyclonic eddies are a little more than the same scale anticyclonic eddies in northwest of Luzon. The temporal distribution of eddy number in the NSCS has a close relation with the Asian monsoon. The number of the large and medium eddies peaks during the winter monsoon, while the submesoscale eddies are apt to generate in the summer monsoon. The spatial and temporal patterns have a good agreement with the results of the sea surface height anomaly (SSHA). The maximum and mean tangential velocities of anticyclones (cyclones) are 40 (30) cm s -1 and 25 (15) cm s -1, respectively. The calculated normalized vorticities from drifters suggest that although the mesoscale eddies may be considered in geostrophic balance, ageostrophic dynamics and centrifugal effects may play an important role for the growth and decay of the mesoscale cores. © Author(s) 2011.

Li J.-X.,PLA University of Science and Technology | Zhang R.,PLA University of Science and Technology | Jin B.-G.,Beijing Applied Institute of Meteorology | Wang H.-Z.,PLA University of Science and Technology
Journal of Marine Science and Technology | Year: 2012

Possibility estimation of generating internal waves has been recognized as a difficult problem because of the complex generation mechanisms and insufficient in situ observation data of internal waves. In this study, a inference model based on the fuzzy logic technique was developed for estimating the generation possibility of internal waves. The marine environmental factors causing the occurrence of internal waves were distilled from ocean data and used as the inputs of the fuzzy inference model, and the generation possibilities of internal waves were used as the output of the model. The developed model was applied to the northwest Pacific, and the results were verified using satellite remote sensing images. The satisfactory results indicate that the inference model based on fuzzy logic is a useful first step in the development of generation estimation of internal waves and can be used as a supplement of traditional methods, which will be helpful for the risk assessment of ocean engineering.

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