In the nighttime stable boundary layer (SBL), shear and turbulence are generated in the layer between the maximum of the low-level jet (LLJ) and the earth's surface. Here, it is investigated whether gross properties of the LLJ-its height and speed-could be used to diagnose turbulence intensities in this subjet layer. Data on the height and speed of the LLJ maximum were available at high vertical and temporal resolution using the high-resolution Doppler lidar (HRDL). These data were used to estimate a subjet layer shear, which was computed as the ratio of the speed to the height of the jet maximum, and a jet Richardson number Ri J , averaged at 15min intervals for 10 nights when HRDL LLJ data were available for this study. The shear and Ri J values were compared with turbulence kinetic energy (TKE) values measured near the top of the 60-m tower at the Cooperative Atmosphere-Surface Exchange Study-1999 (CASES-99) main site. TKE values were small for Ri J greater than 0.4, but as Ri J decreased to less than ϳ0.4, TKE values increased, indicating that Ri J does have merit in estimating turbulence magnitudes. Another interesting finding was that shear values tended to cluster around a constant value of 0.1 s Ϫ1 for TKE values that were not too small, that is, for TKE greater than ϳ0.1 m 2 s Ϫ2 .

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