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Annales Geophysicae An interactive open-access journal of the European Geosciences Union
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Discussion papers | Copyright
https://doi.org/10.5194/angeo-2018-71
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Regular paper 17 Jul 2018

Regular paper | 17 Jul 2018

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This discussion paper is a preprint. It is a manuscript under review for the journal Annales Geophysicae (ANGEO).

Dependence of the critical Richardson number on the temperature gradient in the mesosphere

Michael N. Vlasov and Michael C. Kelley Michael N. Vlasov and Michael C. Kelley
  • School of Electrical and Co mputer Engineering, Cornell University, Ithaca, NY 14853, USA

Abstract. Maximum upper atmospheric turbulence results in the mesosphere from convective and/or dynamic instabilities induced by gravity waves. For the first time, by comparing the vertical accelerations induced by wind shear and the buoyancy force, it is shown that the critical Richardson number Ric can be estimated. Dynamic instability is developed for Ri<Ric. This new approach, for the first time, makes it is possible to establish and estimate the temperature gradient impact on dynamic instability development. Regarding our results, Ric increases from 0.25 to 0.38 as the negative temperature vertical gradient increases from ∂T/∂z=0 to ∂T/∂z−9K/km. However, Ric for the temperature, independent of altitude, is 0.25, coinciding exactly with the Ric commonly used and estimated in classical studies (Miles, 1961; Howard, 1961) and subsequent papers without the temperature impact. The increase in the Ric value strongly influences cooling, inducing the cooling rate increase. Also, our results show that criterion Ric<0.25 can only be used for the turbulent diffusion, which is characterized by eddies with sizes much smaller than the scale height of the atmosphere. The Ric value increases with the increasing size of the eddies, but the term eddy diffusion cannot be applied to transport due to the large-scale eddies (Vlasov and Kelley, 2015).

Michael N. Vlasov and Michael C. Kelley
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Michael N. Vlasov and Michael C. Kelley
Michael N. Vlasov and Michael C. Kelley
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Short summary
Maximum upper atmospheric turbulence results in the mesosphere from convective and/or dynamic instabilities induced by gravity waves. For the first time, by comparing the vertical accelerations induced by wind shear and the buoyancy force, it is shown that the critical Richardson number can be estimated. This new approach, for the first time, makes it is possible to establish and estimate the temperature gradient impact on dynamic instability development.
Maximum upper atmospheric turbulence results in the mesosphere from convective and/or dynamic...
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