EGU22-8277
https://doi.org/10.5194/egusphere-egu22-8277
EGU General Assembly 2022
© Author(s) 2022. This work is distributed under
the Creative Commons Attribution 4.0 License.

Scale-to-Scale Energy and Enstrophy Fluxes of Atmospheric Motions via CFOSAT

Yang Gao1,2, Francois G. Schmitt2, Jianyu Hu1,3, and Yongxiang Huang1,3,4
Yang Gao et al.
  • 1State Key Laboratory of Marine Environmental Sciences, College of Ocean and Earth Sciences, Xiamen University, Xiamen 361102, China
  • 2CNRS, Univ. Lille, Univ. Littoral Cote d'Opale, UMR 8187, LOG, Laboratoire d'Oc\'eanologie et de G\'eosciences, F 62930 Wimereux, France
  • 3Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai), Zhuhai 519000, China
  • 4SJTU SMSE-Mingguang Joint Research Center for Advanced Palygorskite Materials, Mingguang 239400, China

Turbulence theory essentially describes energy and enstrophy flows crossing scales or a balance between input and output. A famous example is the Richardson-Kolmogorov forward energy cascade picture for three-dimensional homogeneous and isotropic turbulence. However, due to the complexity of turbulent systems, and the lack of an efficient method to describe the cascade quantitatively, the factual cascade features for most fluids are still unknown. In this work, an improved Filter-Space-Technique (FST) is proposed to extract the energy flux ΠE, and enstrophy flux ΠΩ between different scales for the ocean surface wind field which was remotely sensed by the China-France Oceanography Satellite (CFOSAT). With the improved FST method, ΠE and ΠΩ can be calculated for databases which contain gaps or with irregular boundary conditions. Moreover, the local information of the fluxes are preserved. A case study of the typhoon Maysak (2020) shows both inverse and forward cascades for the energy and enstrophy around the center of the typhoon, indicating a rich dynamical pattern. The global views of ΠE and ΠΩ for the wind field are studied for scales from 12.5 to 500 km. The results show that both ΠE and ΠΩ are hemispherically symmetric, with evident spatial and temporal variations for all the scales. More precisely, positive and negative ΠE  are found for the scales less and above 60 km, respectively. As for ΠΩ, the transition scale is around 150 km, forward and backward cascades are corresponding to the scales below and above this scale. In the physical space, stronger fluxes are occurring in midlatitudes than the ones in tropical regions, excepts for a narrow region around 10oN, where strong fluxes are observed. In the temporal space, the fluxes in winter are stronger than the ones in summer. Our study provides an improved approach to derive the local energy and enstrophy fluxes with complex field observed data. The results presented in this work contribute to the fundamental understanding of ocean surface atmospheric motions in their multiscale dynamics, and also provide a benchmark for atmospheric models.

 

Ref. 

Alexakis, A., & Biferale, L. (2018). Cascades and transitions in turbulent flows. Phys. Rep., 767, 1-101.

Dong, S., Huang, Y.X., Yuan, X., Lozano-Durán, A. (2020). The coherent structure of the kinetic energy transfer in shear turbulence. J. Fluid Mech., 892, A22.

Frisch, U., Kolmogorov, A. N. (1995). Turbulence: the legacy of AN Kolmogorov. Cambridge University Press.

Gao, Y. , Schmitt, F.G., Hu,  J.Y. &  Huang, Y.X. (2021) Scaling analysis of the China France Oceanography Satellite along-track wind and wave data. J. Geophys. Res. Oceans, 126:e2020JC017119

 

How to cite: Gao, Y., Schmitt, F. G., Hu, J., and Huang, Y.: Scale-to-Scale Energy and Enstrophy Fluxes of Atmospheric Motions via CFOSAT, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8277, https://doi.org/10.5194/egusphere-egu22-8277, 2022.

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