A numerical model of gravity wave breaking and stress in the mesosphere

Abstract

The stresses generated by breaking gravity waves in the mesosphere are calculated with a numerical model of steady vertically propagating gravity waves that includes wavelength dependent radiative dissipation and turbulent viscosity and conduction. The principal findings are (1) waves do not break for |ū ‐ c| values ≲20 m s−1 as radiative damping prevents wave amplitude growth with altitude for short vertical wavelengths; (2) the downward heat flux due to turbulence of breaking waves and turbulent heating through loss of wave energy could severely affect the global radiative energy balance; and (3) predicted zonal deceleration for steady breaking waves is stronger than required by Apruzese et al. (1982) for the mean circulation. Gravity wave breaking may be an intermittent process; otherwise, gravity wave stresses would produce an adiabatic mesosphere with a zonal mean velocity close to the phase speed of the breaking wave. Diffusive transport of constituents and potential temperature by breaking gravity wave turbulence is shown to be important. In the cases of nitric oxide and atomic oxygen the vertical eddy diffusion coefficients are shown to be sensitive functions of their respective chemical loss rates in the mesosphere and lower thermosphere.

Uranus after Solstice: Results from the 1998 November 6 Occultation

“…They are distinct from either the direct deposition of the wave energy flux during dissipation, or the cooling that results from turbulent heat flux. The sum of these two competing effects leads to a heating or cooling rate that is proportional to N 2 D/2c p (0.3 K yr −1 ), where the constant of proportionality can be either positive or negative, depending on unknown parameters such as the eddy Prandtl number and the vertical variation of eddy diffusion (Strobel et al 1985, Schoeberl et al 1983. Therefore, on Uranus as on Earth, waves may affect mesospheric temperatures more through momentum transport than through energy transport.…”

The Impact of Gravity Wave Drag and Diurnal variability on the General Circulation of the Middle Atmosphere

“…The potential improvement achievable in the simulation of the zonal mean characteristics of the middle atmosphere by this parameterization have been demonstrated by Schoeberl et al (1983) and Holton (1983) using zonally symmetric models.…”

“…Recently Lindzen (1981) gave a heuristic derivation for a parameterization of the dissipation induced by breaking internal gravity waves, and subsequently Schoeberl et al (1983) have produced a more rigorous proof. The potential improvement achievable in the simulation of the zonal mean characteristics of the middle atmosphere by this parameterization have been demonstrated by Schoeberl et al (1983) and Holton (1983) using zonally symmetric models.…”

On the Mean Wind Induced by Internal Gravity Wave Packets in the Atmosphere

“…If these assumptions are violated, the buoyancy flux associated with internal gravity waves may appear and the two dimensionality of the induced field may be broken, and the baroclinic adjustment may occur and inertio-gravity waves and/or baroclinic Rossby waves may be induced around the wave packets. Recently, Schoeberl et al (1983) indicate that the cooling associated with breaking internal gravity waves is important in the heat budget of the upper mesosphere.…”

“…The models of the middle atmosphere circulation (e. g., Leovy, 1964;Schoeberl and Strobel, 1978;Holton and Wehrbein, 1980) all required a Rayleigh friction to obtain realistic mean zonal wind and zonal mean temperature distributions around the mesopause (weak mean zonal winds, the highest temperature at the winter pole and the lowest temperature at the summer pole, e. g., CIRA, 1972).…”