During October 1982. the United States Environmental Protection Agency (US EPA) earned out a series of eleven tracer gas experiments near Farmington, New Mexico, in the United States . Hogback Ridge is a small hill with maximum elevation 104 m above the minimum elevation in the area. The terrain is semi-arid, with sparse vegetative cover of desert shrubs and grasses.
Tracer gases (SF6 and 13B1) were released from points on the side of Hogback Ridge, and 100 samplers were arranged along the nearside of the top of the ridge to collect measurements of these tracer gases.
Among the data available from the US EPA experiments are hourly measured meteorological parameters at various heights on a tower (tower A) located at the base of the ridge, hourly measurements of SF6 (ppt) at the 100 samplers and location data for the samplers and tracer release points.
Experiments 4. 10 and 12 have been modelled using the air pollution dispersion model ADMS. and the results compared with the measured concentrations of SFe. These three experiments represent stable (experiment 4) and convective meteorological conditions (experiments 10 and 12).
This document compares the predictions by two versions of ADMS with observed concentrations of SF6-. The two versions are ADMS 184.108.40.206 (hereafter referred to as ADMS 5.0) with those of ADMS 220.127.116.11 (hereafter referred to as ADMS 4.2).