Effects of mesoscale eddies on the internal solitary wave propagation
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Effects of mesoscale eddies on the internal solitary wave propagation LIAO Guanghong1,2∗ , YANG Chenghao1 , XU Xiaohua1 , SHI Xingang3 , YUAN Yaochu1 , HUANG Weigen2 1
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State Key Laboratory of Satellite Ocean Environment Dynamics, Second Institute of Oceanography, State Oceanic Administration, Hangzhou 310012, China College of Information Science and Technology, Ocean University of China, Qingdao 266100, China Beijing Branch of China National Offshore Oil Corporation Energy Technology and Services Limited, Beijing 100027, China
Received 4 April 2012; accepted 14 May 2012 ©The Chinese Society of Oceanography and Springer-Verlag Berlin Heidelberg 2012
Abstract The mesoscale eddy and internal wave both are phenomena commonly observed in oceans. It is aimed to investigate how the presence of a mesoscale eddy in the ocean affects wave form deformation of the internal solitary wave propagation. An ocean eddy is produced by a quasi-geostrophic model in f -plane, and the one-dimensional nonlinear variable-coefficient extended Korteweg-de Vries (eKdV) equation is used to simulate an internal solitary wave passing through the mesoscale eddy field. The results suggest that the mode structures of the linear internal wave are modified due to the presence of the mesoscale eddy field. A cyclonic eddy and an anticyclonic eddy have different influences on the background environment of the internal solitary wave propagation. The existence of a mesoscale eddy field has almost no prominent impact on the propagation of a smallamplitude internal solitary wave only based on the first mode vertical structure, but the mesoscale eddy background field exerts a considerable influence on the solitary wave propagation if considering high-mode vertical structures. Furthermore, whether an internal solitary wave first passes through anticyclonic eddy or cyclonic eddy, the deformation of wave profiles is different. Many observations of solitary internal waves in the real oceans suggest the formation of the waves. Apart from topography effect, it is shown that the mesoscale eddy background field is also a considerable factor which influences the internal solitary wave propagation and deformation. Key words: mesoscale eddy, internal solitary wave, variable-coefficient extended Korteweg-de Vries equation, wave deformation
2008). At the highest latitudes this deformation radius is order 10 km, and at mid-latitudes order 100 km. Their time scale is about 100 d. Internal waves occur on many scales varying from inertial periods down to the buoyancy period (typically 10 min). They primarily arise from the interaction between the tidal current and the topography (Liu et al., 1985; Farm and Armi, 1999; Baines, 2007; Cai et al., 2010). The observed nonlinear internal waves in the ocean frequently occur as solitary internal waves, for example, in the Sulu Sea (Apel, 1985) and the northern South China Sea (Ramp et al., 2004; Yang et al., 2004; Cai et al., 2012), and the wave amplitude is more than 100 m and the soli-
1 Introduction Internal waves and mesoscale eddies are p
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