The 440-MHz radar at Millstone Hill (42.6 ¿N,71.5 ¿W) was employed to examine the detailed evolution of turbulence structures in the tropostratosphere with a very fine Doppler resolution of 0.12 Hz, corresponding to 4 cm s-1 radial velocity resolution. The measurement technique involved directing the antenna downwind at a low elevation angle (15¿ or 20¿) and processing the echos from a range where the background wind shear was high. Although no attempt was made to obtain good range resolution, a wide variety of turbulence structures were evident by virtue of their different Doppler shifts in the presence of a high wind shear. Using arguments based on the dominance of 'shear broadening' and the required velocity gradient to create instabilities, maximum layer thicknesses in the vicinity of 20--300 m were inferred. The implication of these observations to bulk transport of passive contaminants in the stratosphere is briefly discussed.