We present the detailed results of ground-based mesospheric water vapor measurements obtained by microwave spectroscopy at the Jet Propulsion Laboratory (JPL) from December 1984 to April 1985 (JPL 1984-85), and an overview of results obtained the previous year from April to June 1984 (published by Bevilacqua et al., 1985). The JPL 1984/85 spectral data appeared to contain an instrumental baseline curvature which we were able to bracket and remove. In general, the JPL 1984/85 results are in good agreement with those of our previous measurements. They indicate water vapor mixing ratios between 6 and 8 ppmv at 60 or 65 km and falling off steeply with height above this point to values of less than 2 ppmv at 80 km. In addition, there is a large amount of day-to-day variability indicated in the data. A major result of the study is that we find that both the observed vertical gradient of water vapor mixing ratio and its seasonal variation are consistent with the hypothesis that vertical transport time scales are smaller, perhaps by an order of magnitude, than values currently used in both one- and two-dimensional photochemical/dynamical models. ¿American Geophysical Union 1987