Study On Ocean Current Data Using Satellite Altimeters And Their Application Of The Kuroshio

The ocean current is the stable flow of the sea water. It has a large impact on various geophysical phenomena such as the transport of heat, salt and chemical factors. And it also greatly impacts the climate and the air-sea exchanges. The ocean surface currents are reconstructed from the altimeter-derived sea surface height and satellite-derived wind data. Next based on the geostrophic current product, the variations of the Kuroshio Current are examined. The main conclusions are summarized as follows:Firstly, the ocean surface currents are reconstructed from the satellite remote sensing data containing altimeter-derived sea surface height and satellite-derived wind data. The global daily 0.25°×0.25° ocean surface current NetCDF product is reconstructed by combining the geostrophic current estimated from sea surface height with the Ekman current estimated from the wind stress. It shows the satellite-derived current product can capture the characteristics of ocean surface currents.Then, based on 20-year(1991-2012) geostrophic current product, the location of the axis and the boundary of the Kuroshio Current are derived using the improved characteristic line method. And the along-stream velocity, section width, along-stream surface transport and path standard deviation of the Kuroshio Current are also derived.Secondly, the derived results show that the along-stream velocity of the Kuroshio increases from a minimum in the winter to a maximum of 0.95 m/s in the summer and autumn. Larger width of mainstream occurs in October and November. The mean surface along-stream transport has a maximum value in the summer, the transport is less in spring and autumn while is least in the winter. The along-stream velocity, section width and along-stream surface transport are decomposed by EMD, it shows that they all include 1-, 2-and 5-year cycle. The 1-year cycle represents the seasonal variations of the Kuroshio while the 5-year cycle represents the Kuroshio response from the El Nino. And we find the correlation coefficients for the along-stream velocity and along-stream surface transport of the Kuroshio Current and the Nino3 index that lagged by four months are at most 0.38 and 0.42 respectively.Finally, based on the different regions along the current, we find that the along-stream velocity, section width and along-stream surface transport are increased along the current, while the time when the maximum value of the along-stream velocity and surface transport occur is late. The location of the axis of the Kuroshio Current departs from the annual mean path further and the signal of inter-month oscillation is also stronger along the current. Besides, the correlation coefficients for the along-stream velocity and along-stream surface transport of the Kuroshio Current and the Nino3 index are lower along the current, which reflect the El Nino’s influence on the Kuroshio declines along the current.In addition, the monthly mean water mass exchange of the Kuroshio Current’s boundary for 20 years shows that the Kuroshio Current intrudes from north-east of Taiwan to shelf during the winter. The transport across the boundary of the Kuoshio can exit all over the year in the East China Sea, which makes the along-stream velocity of the Kuroshio continue to grow when it is forwards to the north.