Turbulence and anomalous heat fluxes in the atmospheres of Mars and Venus

Tropospheres of Earth, Mars and Venus are, as a rule, stably stratified. At the same time, turbulence exists, creating constant composition of the atmospheres up to altitudes of 100–150 km. This turbulence is formed mainly via breaking of buoyancy waves (i.e. internal gravity waves), moving from the surface upwards in the atmosphere of a planet. Under such conditions, an anomalous downward turbulent heat flux arises in the troposphere from lower to higher temperatures. This flux affects rather slightly the atmospheres of Earth and Mars, heated by solar radiation basically from their surfaces, but can play an essential role in the thermal balance of the troposphere of Venus. With help of a model, describing the breaking of buoyancy waves moving upwards in planetary atmospheres, and based on experimental data about the turbulent diffusion coefficient at the homopause and at the surface of a planet, the altitude dependence of turbulent diffusion coefficients in the atmospheres of Mars and Venus is found. This dependence is useful for radiative–convective models of the thermal balance of planetary atmospheres.