||The second field study of EPA's Complex Terrain Model Development Program, Small Hill Impaction Study No. 2, was conducted along a 1.5-km section of the Hogback Ridge near Farmington, New Mexico in October 1982. Eleven quantative tracer experiments were performed, each lasting 8 hours at night or early morning. Meteorological data were recorded on two instrumented towers up-wind of the ridge and two towers on the slope. Data were direct and derived measures of wind, turbulence, and temperature averaged at 5-minute and 1-hour intervals. Hourly profiles of wind, temperature, pressure and humidity were recorded at one tethersonde site upwind of the ridge, while another tethersonde was held at the point of tracer release to record wind and temperature at 13-second intervals. Three sets of optical anemometers measured path-average wind speed across the base, slope and crest of the ridge. Tracer gas concentrations, SF6 and Freon 13B1, were detected by a network of 110 sampler sites on the ridge, and the values were recorded as 10-minute and 1-hour concentrations. All data, meteorological and tracer, were stored on magnetic tape files to form an accessible computer data base. Tape files were fully documented to facilitate utilization of the data base for modeling efforts.