Situated between the Andes Cordillera and the Cordillera de la Costa, Santiago, Chile frequently experiences episodes of high concentrations of surface ozone. Levels most hazardous to human and ecosystem health are most often recorded in the summer months of November through February. It is at this time that high temperatures, long duration and intensity of incoming solar radiation, low cloud fraction, minimal mixing, light winds, and low amounts of water vapor strongly favor the production and accumulation of surface ozone in the city. Emissions of volatile organic compounds (VOCs) and nitrogen oxides (NOx) from industrial activities and commuter traffic also contribute to elevated ozone concentrations. Other authors have documented intraseasonal variability in many of these contributing factors; however, the variability of ozone on that time scale has yet to be studied comprehensively.

The objective of this study is to therefore analyze the variability of surface ozone concentrations in Santiago by phase of the leading mode of atmospheric intraseasonal variability, the Madden Julian Oscillation (MJO). Data from six observing stations in the Santiago metropolitan region will be tested to see if statistically significant relationships between ozone level and MJO phase exist. Values for the summer months from 1987-2011will be used. Composite anomalies of temperature, lower-troposphere wind, mixing height, cloud fraction, and water vapor will be examined for each MJO phase to determine if any of these variables are related to surface ozone on the timescale of the MJO.