Constrains on gravity wave induced diffusion in the middle atmosphere |
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Authors: | Darrell F Strobel |
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Institution: | (1) Department of Earth and Planetary Sciences, Department of Physics and Astronomy, The Johns Hopkins University, 21204 Baltimore, MD, U.S.A. |
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Abstract: | A review of the important constraints on gravity wave induced diffusion of chemical tracers, heat, and momentum is given. Ground-based microwave spectroscopy measurements of H2O and CO and rocket-based mass spectrometer measurements of Ar constrain the eddy diffusion coefficient for constituent transport (K
zz
) to be (1–3)×105 cm2s–1 in the upper mesosphere. Atomic oxygen data also limitsK
zz
to a comparable value at the mesopause. From the energy balance of the upper mesosphere the eddy diffusion coefficient for heat transport (D
H
) is, at most 6×105 cm2s–1 at the mesopause and decreasing substantially with decreasing altitude. The available evidence for mean wind deceleration and the corresponding eddy diffusion coefficient for momentum stresses (D
M
) suggests that it is at least 1×106 cm2s–1, in the upper mesosphere. Consequently the eddy Prandtl number for macroscopic scale lengths is >3. |
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Keywords: | Gravity waves turbulence heat transport tracer transport eddy diffusion mesosphere |
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