Analytical Model for the Generation of Vorticity Caused by Inhomogeneous Friction on the Underlying Surface

In a number of recent publications, attention is drawn to the heterogeneity of the underlying surface as a factor that can contribute to the genesis and intensification of tornadoes. This paper proposes an analytical model for the generation of vorticity under the influence of horizontally inhomogeneous friction. The resulting vorticity is proportional to the background flow velocity and to the horizontal gradient of the drag coefficient transverse to this flow; the dependence on other factors is relatively weak. Numerical estimates show the possibility of efficient vorticity generation.