The vortex gas scaling regime of baroclinic turbulence
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4491.full.pdf
Description
Published version
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1.21 MB
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Adobe PDF
Checksum (MD5)
9bba434b459c2bfc61080a2fbda39a8a
Author(s)
Gallet, Basile
Ferrari, Raffaele
Date Issued
February 2020
Journal
Proceedings of the National Academy of Sciences
Publisher
National Academy of Sciences
Citation
Gallet, Basile and Raffaele Ferrari. "The vortex gas scaling regime of baroclinic turbulence." Proceedings of the National Academy of Sciences (February 2020): 4491-4497 © 2020 National Academy of Sciences
Version
Final published version
Abstract
The mean state of the atmosphere and ocean is set through a balance between external forcing (radiation, winds, heat and freshwater fluxes) and the emergent turbulence, which transfers energy to dissipative structures. The forcing gives rise to jets in the atmosphere and currents in the ocean, which spontaneously develop turbulent eddies through the baroclinic instability. A critical step in the development of a theory of climate is to properly include the eddy-induced turbulent transport of properties like heat, moisture, and carbon. In the linear stages, baroclinic instability generates flow structures at the Rossby deformation radius, a length scale of order 1,000 km in the atmosphere and 100 km in the ocean, smaller than the planetary scale and the typical extent of ocean basins, respectively. There is, therefore, a separation of scales between the large-scale gradient of properties like temperature and the smaller eddies that advect it randomly, inducing effective diffusion. Numerical solutions show that such scale separation remains in the strongly nonlinear turbulent regime, provided there is sufficient drag at the bottom of the atmosphere and ocean. We compute the scaling laws governing the eddy-driven transport associated with baroclinic turbulence. First, we provide a theoretical underpinning for empirical scaling laws reported in previous studies, for different formulations of the bottom drag law. Second, these scaling laws are shown to provide an important first step toward an accurate local closure to predict the impact of baroclinic turbulence in setting the large-scale temperature profiles in the atmosphere and ocean.
MIT Department
Massachusetts Institute of Technology. Department of Earth, Atmospheric, and Planetary Sciences
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DOI of Published Version
https://doi.org/10.1073/pnas.1916272117
