Cone models of mountain peaks associated with atmospheric vortex streets

The shedding of atmospheric vortex streets from mountain peaks has been simulated in the wakes of several shapes of circular cones and one combination of two such cones placed in the uniform, unstratified flow of a wind tunnel. Conditions for vortex shedding are more favorable the steeper the slopes of the peaks. From the laboratory measurements and with the assumption of Reynolds number independence, predictions are made of the periodicities of vortex shedding from six volcanic peaks whose periodicities of vortex shedding have been determined by others from satellite photographs of wake clouds. The predicted periods agree with the measured periods in three cases and are significantly smaller in three cases. For the latter cases it is concluded that stratification has so altered the atmospheric flow that either the Strouhal number has been lowered or the barrier effect of the topographic obstacle has been considerably enhanced. It is also concluded that stratification sufficient to reduce turbulence is necessary for the existence of an extended atmospheric vortex street.