Parametrization of momentum and energy depositions from gravity waves generated by tropospheric hydrodynamic sources

Abstract

Abstract. The mechanism of generation of internal gravity waves (IGW) by mesoscale turbulence in the troposphere is considered. The equations that describe the generation of waves by hydrodynamic sources of momentum, heat and mass are derived. Calculations of amplitudes, wave energy fluxes, turbulent viscosities, and accelerations of the mean flow caused by IGWs generated in the troposphere are made. A comparison of different mechanisms of turbulence production in the atmosphere by IGWs shows that the nonlinear destruction of a primary IGW into a spectrum of secondary waves may provide additional dissipation of nonsaturated stable waves. The mean wind increases both the effectiveness of generation and dissipation of IGWs propagating in the direction of the wind. Competition of both effects may lead to the dominance of IGWs propagating upstream at long distances from tropospheric wave sources, and to the formation of eastward wave accelerations in summer and westward accelerations in winter near the mesopause.

Numerical and the MU radar estimations of gravity wave enhancement and turbulent ozone fluxes near the tropopause

“…These characteristics, as well as coefficients of turbulent viscosity and heat conduction and dissipation of IGW harmonics at critical and reflection levels, are calculated here, as described by . The influence of the critical layers leads, in the model, to stronger dissipation of IGW harmonics propagating in the direction of the mean wind and to the predominance of waves propagating in the opposite direction (Gavrilov, 1997). Such IGW filtering provides, in the model, the wave accelerations of the mean flow directed mainly opposite to the direction of the strato-mesospheric winds in the middle atmosphere (Gavrilov, 1997), which is consistent with recent views (Fritts and Alexander, 2003).…”

“…where s is the strength of wave sources (see Gavrilov, 1997); N d is the rate of IGW dissipation. The main contributions to dissipation rate N d are from turbulent and molecular viscosity and heat conduction, radiative heat exchange, and ion drag (see Gavrilov, 1990).…”

Medium‐frequency radar studies of gravity‐wave seasonal variations over Hawaii (22°N, 160°W)

“…These characteristics, as well as coefficients of turbulent viscosity and heat conduction and dissipation of IGW harmonics at critical and reflection levels, are calculated here as described by Gavrilov and Fukao [1999]). Influence of the critical layers leads in the model to stronger dissipation of IGW harmonics propagating in the direction of the mean wind and to the predominance of waves propagating in opposite direction [see Gavrilov, 1997]. Such IGW filtering provides in the model the wave accelerations of the mean flow directed mainly opposite to the direction of the stratomesospheric winds in the upper middle atmosphere [Gavrilov, 1997], which is consistent with recent views [Fritts and Alexander, 2003].…”

“…Therefore an increase in B 1 is mainly equivalent to larger relative strengths of sources of eastward propagating IGW in the model. These IGWs are subject of larger filtering out by eastward background winds in winter stratomesosphere due to stronger dissipation and critical levels [see Gavrilov , 1997]. This leads to smaller the average IGW variances for B 1 = 0.3 in Figures 15 and 16 in winter compared to that for B 1 = 0.…”

Gravity wave intensity and momentum fluxes in the mesosphere over Shigaraki, Japan (35°N, 136°E) during 1986-1997

“…Theoretical estimations and numerical modelling (Gavrilov, 1997) show that IGWs propagating in the direction of the mean wind have smaller vertical wavelengths and larger dissipation than analogous IGWs propagating opposite to the mean wind. The net IGW momentum¯ux is a vector sum of momentum¯uxes produced by individual IGW components.…”