Lin parameter as characteristic of atmospheric vortex streets.

Abstract

Atmospheric Vortex Streets T vortex patterns of Figs. 1 and 2, leeward of the Canary islands, were revealed by the TIROS weather satellites. These patterns, consisting of vortices of radii ~ 10-20 km in wakes 40-50 km wide and 400-500 km long, were observed to persist for 18 to 30 hr. Chopra and Hubert' identified these eddy patterns as the atmospheric analogs of the well-known vortex street phenomenon in which the vortices are shed alternately from each side of the obstacle to the ambient flow and arrange themselves in two rows in such a way that: a) the vortices in one row have similar circulations of the sense opposite to that of the vortices in the other row; and b) each vortex in one row is located across the midpoint of the two adjacent vortices in the second row. The theory developed by Chopra and Hubert explained the observed features of Figs. 1 and 2 and made the following predictions: 1) The coefficient of eddy viscosity in the wake region is about 10m/sec; and 2) The vortices are shed alternately from each side of the island generating the wake at a rate of about one every 7-8 hr. Eddy viscosity is a property of fluid flow, and it is known to vary from 10 m/sec to 10m/sec. Zimmerman has provided support for the prediction regarding the frequency of shedding through observations on pressure fluctuations around the Island of Tenerife. Since the Chopra-Hubert explanation of the Canary vortices, evidence for the island-generated atmospheric vortex streets has been mounting. Gemini VI and IX missions photographed