Abstract
observations of waterspouts and tornadoes suggest some influence of surface roughness on these phenomena. In a laboratory model of a tornado-like vortex, this influence is measured in terms of tangential and vertical velocity profiles above the ground boundary layer. The roughness induces an increase of the core updraft, and the effect on the tangential velocity profile is such as to increase the radial Reynolds number.
In the atmosphere, geometrical similarity suggests that passing over forests or towns could greatly affect tornadoes, increasing the core diameter and mean updraft, but suddenly decreasing the explosive effects and wind speeds.
