Derivation of the thermal characteristics of mesoscale eddies
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Derivation of the thermal characteristics of mesoscale eddies CHEN Xuan1, PAN Jing2, ZHENG Chongwei2, 3, 4*, ZHANG Xi4, HE Ming5 1 The 75839 Army, People’s Liberation Army, Guangzhou 510510, China 2 National Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics (LASG),
Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029, China 3 Dalian Naval Academy, People’s Liberation Army, Dalian 116018, China 4 College of Meteorology and Oceanography, People’s Liberation Army University of Science and Technology,
Nanjing 211101, China 5 College of Marine Life Science, Ocean University of China, Qingdao 266003, China
Received 21 January 2016; accepted 29 March 2016 ©The Chinese Society of Oceanography and Springer-Verlag Berlin Heidelberg 2017
Abstract
This study aims at explaining the relationship between thermodynamic characteristics and direction of rotation of mesoscale eddies (MEs). The geometric characteristics of the MEs are under the following assumptions: the structure of the MEs is symmetrical, and changes of oceanic physical variables are close to linear features in the radial direction in the ME regions. Based on these assumptions, by using primitive equations without friction under a cylindrical coordinate system, the thermodynamic characteristics of the MEs are derived, showing that the conventional relationship of warm anticyclonic eddies with high sea surface height (SSH) and cold cyclonic eddies with low SSH is not consistent with the SSH and sea surface temperature (SST) observations of eddies. The results show that the symmetrical form is an ideal approximation for the geometric characteristics of MEs. In consideration of the above assumptions, there are advantages for derivation of the characteristics of the MEs under a cylindrical coordinate. Key words: mesoscale eddies, thermodynamic characteristics, symmetry Citation: Chen Xuan, Pan Jing, Zheng Chongwei, Zhang Xi, He Ming. 2017. Derivation of the thermal characteristics of mesoscale eddies. Acta Oceanologica Sinica, 36(3): 8–13, doi: 10.1007/s13131-017-1036-9
1 Introduction Mesoscale eddies (MEs) are some of the most important oceanographic phenomena. They are critical factors for ocean dynamic, thermodynamic and marine chemical processes. The MEs also are of significant impact on the ocean energy development, climate variation and so on (Zheng et al., 2013a, b, 2016; Zheng and Pan, 2014). By analyzing sea surface observations, a large number of eddies are found almost everywhere (Thorpe, 2007; Chelton et al., 2011). The energy transfer from the general circulation to the MEs is largely a consequence of barotropic and baroclinic instabilities with a flux about 1 TW (Thorpe, 2007). The energy from wind is substantial (Zheng and Pan, 2014), and the MEs are further supported by the wind energy flux about 0.2 TW, which can sustain a total energy in the mesoscale field of about 13 EJ (Thorpe, 2007). The MEs have great influence on the spatial distribution of oceanic physical variables (Xu et
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