Meteorological conditions during the 1985 southern California nitrogen species methods comparison study

The purpose of this paper is to present a summary of meteorological conditions which occurred during the Nitrogen Species Methods Comparison Study, conducted in Claremont, California, between 11 and 18 September 1985. This information is intended as an introduction for subsequent articles which describe the results of the study.In southern California, September is noted for hot weather, stagnant air, and high concentrations of photochemical air pollution. During mid-September 1985, however, meteorological conditions were unusually favorable for the dispersion of pollutants, with an abnormally strong upper level trough over southern California at the beginning and again at the end of the intercomparison study period. These troughs were accompanied by much cooler and less stable air than would be desirable for a nitrogen species study. Only the four-day period of 12–15 September could be categorized as somewhat typical of September weather.