The most typical shape of oceanic mesoscale eddies from global satellite sea level observations

Abstract

In this research, we normalized the characteristics of ocean eddies by using satellite observation of the Sea Level Anomaly (SLA) data to determine the most typical shape of ocean eddies. This normalization is based on modified analytic functions with nonlinear optimal fitting. The most typical eddy is the Taylor vortex (~50%), which exhibits a Gaussian-shaped exp(-r²) SLA and a vorticity distribution of (1-r²)exp(-r²) as a function of the normalized radii r. The larger the amplitude of the eddy, the more likely the eddy is to be Gaussian-shaped. Furthermore, approximately 40% of ocean eddies are combinations of two Gaussian eddies with different parameters, but the composition of these types of eddies is more like a quadratic eddy than a Gaussian one. Only a small portion of oceanic eddies are pure quadratic eddies (<10%) with the same vorticity distribution as a Rankine vortex. We concluded that the Taylor vortex is a good approximation of the typical shape of ocean eddies.

Keywords

sea level anomaly / ocean eddies / Taylor vortex / typical shape

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Acknowledgements

We thank the three anonymous reviewers for their constructive suggestions. This work was supported by the National Basic Research Program of China (Nos. 2012CB417402 and 2013CB430303) and the National Natural Science Foundation of China (Grant Nos. 41376017 and 41205126) and the Open Research Fund of Key Laboratory of Atmospheric Composition and Optical Radiation of Chinese Academy of Sciences (Grant No. JJ1102). We thank AVISO for providing the SLA data and the open fund of State Key Laboratory of Satellite Ocean Environment Dynamics (No. SOED1501).

RIGHTS & PERMISSIONS

2014 Higher Education Press and Springer-Verlag Berlin Heidelberg