Extended Abstract (72K)J5.8
Ozone Trends and Characteristics of Ozone Episodes in Corpis Christi, Texas
Sunil Kumar, Texas A&M University, Kingsville, TX; and K. John
Corpus Christi is a semi-arid coastal urban area located in south Texas. Although Corpus Christi is still in attainment of the 1-hour National Ambient Air Quality Standard (NAAQS) for ozone prescribed by the United States Environment Protection Agency (US EPA), it is very close to the new 8-hour ozone standard recently prescribed by the agency. Therefore, it has been termed as a near nonattainment area. This study presents the characteristics of high ozone episodes for this urban area. In this study, we have analyzed the ozone concentration data from two available monitoring stations (CAMS04 & CAMS21) in the city for the period between 1986-2000. It was found that there were exceedances of the 1-hour NAAQS at CAMS04 during 1990 and 1994 and at CAMS21 during 1987, 1993, and 1995. Significant reductions in the 1-hour ozone levels were observed since 1995. Exceedances of the 8-hour NAAQS (proposed in March 1997) were observed at CAMS21 during 1988 and 1989, but no exceedances were observed at CAMS04 during the study period. Higher frequency of ozone exceedances was noticed during May through September and during weekdays. Predominant wind directions were north and northeast during high ozone days compared to southeast during low ozone days. Wind speeds during low ozone days were usually higher than those observed during high ozone days. We have also studied correlation of ozone levels observed in Corpus Christi with those in Houston, San Antonio, Austin, and Victoria during high ozone episode days. Higher correlation with areas closer to Corpus Christi were observed suggesting spatial homogeneity in ozone distribution on episode days. Back-trajectory analysis using HYSPLIT4 model revealed that on high ozone days in Corpus Christi, the air parcels came over the continent from the northeast suggesting the influence of major urban and industrial regions upwind. Interestingly, it was observed that usually when high ozone levels persist for a few days in Houston, other areas in the region also experience one or two days of high ozone concentrations. Detailed trend analysis was conducted using several statistical techniques for the study region in Texas. It was observed that while the region showed a significant decrease in the one-hour peak ozone levels, most urban areas showed an increase in the eight-hour averaged levels. Rao-Zurbenko method was applied to the long-term time series data and the meteorological influences on the trend discerned for each urban area in Texas.
Joint Session 5, Atmospheric Chemistry (Joint with the Fourth Symp. Urban Environment, 12th Joint Conf. on the Applications of Air Pollution Meteorology with A&WMA, and 25th Conf. Agricultural & Forest Meterology; Cosponsored by the AMS STAC Committee on Atmospheric Chemistry)
Thursday, 23 May 2002, 1:30 PM-4:59 PM
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