Air Quality and Dispersion Meteorology over the Northeastern Gulf of Mexico: Measurements, Analyses, and Syntheses

Meteorological and air quality data recorded during the period of May 1997 through July 1998 is reduced and presented in this final report. The data was acquired from monitoring stations located on Dauphin and Breton Islands in the northeast Gulf of Mexico. It was found that the hourly average pollutant (SO2 and NO2) concentrations at both sites were less than 6 ppb during over half of this reporting period. Weak seasonal and diurnal trends were exhibited at Dauphin Island; the seasonal trend was less evident at Breton Island and diurnal peaks were generally not distinguishable. Maximum concentrations at both SO2 and NO2 at Dauphin Island were primarily associated with wind flow from the north and northeast; maximum SO2 concentrations at Breton were also seen with northerly winds, but NO2 maximums were often recorded under flow from the south and southwest. Unstable atmospheric conditions dominated over the Breton Sound area throughout the year, with free convection being observed as often as 15% of the time. Methods for determining the stability category, turbulence intensity, drag coefficient, and mixed heights from routinely available measurements are described. Computed values are in good agreement with observed data. Both air quality and meteorological results are consistent with findings from datasets previously obtained in this area.