We report results from the analysis of data collected during a field study motivated by the need for air quality models to examine the air quality impact of distributed generating stations located in urban areas. Sulfur hexafluoride, a tracer, was released from the stack of a 650 kW gas fired power plant located in Palm Springs, California, during seven days and nights in July 2008. The short stack is on the top of a 7 m high building surrounded by one story residences. The buoyant tracer release was sampled at ground-level at distances ranging from 40 m to 2000 m from the power plant. Two sonic anemometers at heights of 4 and 10.5 m provided micrometeorological information during the release.

This paper presents the concentrations measured during the tracer study, and relates their spatial and temporal variation to the measured micrometeorology using simple dispersion models as well as AERMOD. The maximum ground-level concentrations occurred within 100 m from the source and were several times higher than those estimated with AERMOD, which accounts for buoyant releases affected by building effects. We suggest modifications to AERMOD to provide a better description of such releases.