Modelling Turbulence Effect in Formation of Zonal Winds

A turbulence-affected mechanism of formation of zonal winds in the Earth’s troposphere is discussed from the perspective of the theory of rotationally anisotropic turbulence (the RAT theory). The turbulence effect is explained as an action of the turbulence rotational viscosity introduced within the RAT theory to characterize the shear in relative rotation (determined as the difference between the average angular velocity of eddy rotation and the vorticity of the average velocity field). The effect manifests in the form of an additive correction to the wind velocity predicted by the geostrophic approach. It is shown that the accounted turbulence effect decreases the westerlies’ velocity predicted by the geostrophic approach at lower latitudes and can be used to explain the formation of easterlies (trade winds) in the equatorial zone without any necessity of assigning the geopotential a local minimum, at the Equator which is required to explain the trade winds within the purely geostrophic approach.