Interannual variations in energy conversion and interaction between the mesoscale eddy field and mean flow in the Kuroshio south of Japan |
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Authors: | Libin Ma Qiang Wang |
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Affiliation: | 1. Key Laboratory of Ocean Circulation and Waves, Institute of Oceanology, Chinese Academy of Sciences, Qingdao, 266071, China 2. University of Chinese Academy of Sciences, Beijing, 100049, China
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Abstract: | Using 19-year satellite altimetric data, variations in the eddy kinetic energy, energy exchanges and interaction between the eddy field and mean flow are discussed for the Kuroshio south of Japan. In the seasonal cycle, the eddy kinetic energy level is a minimum in December/January and a maximum in April/May. In addition to seasonal variations, the eddy kinetic energy undergoes interannual changes. The energy transfers mainly from the mean flow to the eddy field in the Kuroshio south of Japan, and dominant energy exchanges mainly occur along the Kuroshio path south of Japan in each year from 1993 to 2011. In addition, there is often barotropic instability south of Honshu. Regarding interactions between the eddy field and mean flow, cyclonic and anticyclonic accelerations are also found along the Kuroshio path and they flank each other. There is cyclonic acceleration always imposed on southeast of Kyushu, and anticyclonic acceleration dominates south of Honshu from 2001 to mid-2005. Reynolds stress is used to explain the dynamic process of energy exchange. Furthermore, lag-correlation and linear regression analysis show that variability of the energy conversion rate and Reynolds stress involve responses to eddy acceleration at two time scales. The enhanced eddy acceleration induces large Reynolds stress, and enhanced Reynolds stress or barotropic instability further enforces energy transfer from the mean flow to the eddy field. |
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Keywords: | eddy kinetic energy energy conversion rate eddy-mean flow interaction Reynolds stress |
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