Measurements and analysis of ozone production in Houston and Los Angeles



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Ozone is a respiratory irritant that affects all groups of people, but can be of significant concern to young children, those with respiratory illnesses such as asthma, and the elderly. Repeated exposure can cause permanent lung damage. An estimated 123 million people in the Unites States live in regions designated as non-attainment for the 2008 8-hour ozone standard of 75 ppbv. Nearly 5.9 million people live in the Houston-Galveston-Brazoria non-attainment area, and over 15.7 million live in the Los Angeles-South Coast Air Basin non-attainment area. The work presents the results and analysis of measurements collected during several field campaigns in Houston, TX between 2006 and 2012, as well as in Pasadena, CA (CalNex) in the summer of 2010. Part one focuses on the comparison of O3, CO, NO, and NO2 measured continuously at two heights on the UH main campus in the fall of 2011 and 2012 and finds that the titration of O3 to NO2 accounts for ~50% of the observed nighttime differences on average, while it accounts for nearly 100% of the differences during some mornings. The second part presents the results of photochemical box modeling of O3 production rates during three campaigns in Houston and during CalNex, which shows the effects of VOC reductions on O3 production and the differences between the spring and fall O3 seasons in Houston. Finally, an examination of the NOy budget during CalNex and the impacts that the choice of classification of days has on the analysis will be discussed reports that the overall agreement between measured NOy and the sum of individual NOy species is good, and that distinctly different results for calculated O3 production efficiencies are found depending on which classification method is applied to the measurements.



NOx-sensitivity, Ozone production, Ozone measurements, Urban air quality, SHARP, TRAMP, CalNex