The influence of meteorology and atmospheric composition on the year-to-year variability in the number of ozone exceedances in Houston

Over the past decade Houston air quality has improved significantly with fewer air quality exceedance days and lower peak pollution levels. Nevertheless, Houston still experienced 47 ozone exceedances days in 2011 with significant year-to-year variability in the past few years in both the peak ozone and the number of ozone days per year. For example, in 2005 Houston experienced 86 days where ambient ozone was above the 8-hr averaged 75 ppbv standard compared to only 28 in 2009. In this study we characterize various meteorological variables including windspeed, temperature, wind direction, and solar irradiance on both high and low ozone days over the past several years. Furthermore, the long term trends in the atmospheric mixing ratios of nitrogen oxides and volatile organic compounds are analyzed to determine the degree to which the regional changes in these photochemical ozone precursors are responsible for the year to year variability in both peak ozone and the number of ozone events observed in a given year.