Colorado Front Range Ozone Analysis

Audra McClure-Begley (1,2), Irina Petropavlovskikh (1,2), Sam Oltmans (1,2), Jon Kofler (1,2), Gabrielle Petron (1), Brad Pierce (1), Patrick Reddy (5), Arlyn Andrews (1), Hope Humphries (3), Mark Leonard (1,5)

Abstract
The Colorado Northern Front Range Metro Area (NFRMA) is a geographical location that is subject to air quality concerns and frequent exceedances of the National Ambient Air Quality Standards for ozone. Increases in gas and oil extraction and production, population expansion, biomass burning, transported pollution, high levels of UV radiation, and mountain-valley meteorological conditions create an environment which is conducive to the photochemical creation and accumulation of ground based ozone. As one of the main compounds in photochemical smog over the NFRMA, surface ozone levels have a dramatic effect on the oxidation characteristics of the lower atmosphere, public health conditions, and ecosystem functioning of this region. The dynamics of surface ozone are impacted and controlled by not only the precursor pollutants; which provide the chemical foundation for ozone production, but also by the meteorological and environmental conditions that aid in the accumulation of ozone. In the NFRMA summer time, dominant winds from the East and North East with co-located high methane measurements suggest influence on ozone from precursors released by the active gas and oil and agricultural area of Colorado. In contrast, winds from the North and North West sector often suggest influence from wildfire emissions, such as carbon monoxide, or long-range transport. In order to investigate the influence of pollutant sources on ozone trends and high ozone episodes, NOAA-Global Monitoring Division maintains measurements and long-term records of surface ozone and precursor pollutants in the NFRMA from three locations (Erie, Niwot Ridge, and Tundra lab). These locations provide an elevation gradient of ozone measurements, precursor pollutant samples, and meteorological data, which allow for exploration of sources and conditions that allow for build-up of ozone at the surface. These data in combination with NOAA HYSPLIT back-trajectory, NOAA RAQMS model, and NCAR WRF model analysis are used to understand the origins, seasonality, and photochemical processes of air masses moving into the NFRMA. The long-term surface ozone record from NOAA-Global Monitoring Division Colorado measurement sites are analyzed in regard to dominant wind direction and precursor emissions to provide a quantitative, detailed understanding of high ozone episodes in the Colorado Front Range.