Presentation Information
[AAS08-P18]Influence of ENSO Teleconnection on Surface Ozone Exceedances in Colorado’s Northern Front Range
*Joshua Richards1, Gary Morris2, Irina Petropavlovskikh3, Belay Demoz1 (1.University of Maryland, Baltimore County, 2.NOAA Global Monitoring Lab, 3.CIRES)
Keywords:
ozone,ENSO,teleconnections,atmospheric chemistry
The number and magnitudes of ozone exceedance events in the Boulder-Denver Region of Colorado have changed little over the last 25 years, despite many EPA policies and air quality regulations in the region. Our research sought to discover other influences that might contribute to the regular occurrence of ozone exceedances. In particular, in this study, we examine the influence of the El Nino Southern Oscillation (ENSO) teleconnection on air quality within the region. Utilizing 45 years of surface ozone observations from continuous ambient monitoring stations run by the Environmental Protection Agency (EPA), we evaluated these large-scale influences and their relationship to exceedances of the 70 ppbv National Ambient Air Quality Standard (NAAQS) for ozone. Linear regression fits to the daily peak 8-hour average concentrations for each county revealed an increasing trend throughout the selected period. Utilizing the Oceanic Nino Index (ONI) index to distinguish El Nino, La Nina, and neutral phases of ENSO, and removing an overall increasing trend in ozone revealed an earlier onset of the summer ozone season (May-Aug) during El Nino. We perform statistical analyses to further explore this finding and examine how meteorological conditions associated with El Nino may increase surface ozone in June in the region. One of the potential factors would be El Nino’s influence on the North American Monsoon. A delay in the onset of the North American Monsoon (NAM) during El Nino events could cause decreased cloud cover and precipitation leading to more radiative energy reaching the surface making it more favorable to have an ozone exceedance event.