Radar observations show that thin persistent layers of turbulence occur sporadically in the troposphere and stratosphere. Two probabilistic approaches are used to show that the vertical eddy diffusivity due to such layers is of the order of 0.2‐0.3 m²/sec in the lower stratosphere. An actual realization of turbulent layers, derived from the radar observations at Arecibo, is used in a numerical approach to obtain a profile of eddy diffusivity. It is suggested that turbulence plays a significant role in the vertical transport of trace constituents in the stratosphere. Copyright 1984 by the American Geophysical Union.