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Ambient ozone is influenced by meteorology in addition to concentrations of precursor compounds (oxides of nitrogen (NOx) and volatile organic compounds (VOC)). The efficacy of regulatory measures in nonattainment areas, such as the Houston-Galveston-Brazoria (HGB) area of Texas, can be efficiently evaluated by separating the meteorologically induced variability from ozone data. This study applies the Kolmogorov-Zurbenko (KZ) filter for obtaining a temporal resolution of ozone, NOx and VOC data into short-term, seasonal and long-term components, at three stations located near the Houston Ship Channel. Air quality and meteorological data for Clinton (AQS Site ID: 48-201-1035), Deer Park (48-201-1039) and Lynchburg Ferry (48-201-1015) stations were analyzed for the period between 2003 and 2017. A combination of KZ filter and multiple linear regression, with predictor variables (solar radiation, temperature, dew point, and wind speed) is employed to develop meteorologically independent ozone, NOx and VOC trends. This study indicates that variability from meteorology accounts for 51%, 35% and 41% in baseline MDA8 ozone at Clinton, Deer Park, and Lynchburg stations, respectively. For the 15-year study period, long-term MDA8 ozone trends for Deer Park and Lynchburg stations were decreasing at a linear rate of 0.689 ± 0.016, and 0.573 ± 0.019 ppb/yr, respectively. At the Deer Park and Lynchburg stations, a high degree of correlation for meteorologically detrended MDA8 ozone with NOx (ρ: 0.899, 0.678) and VOC (ρ: 0.912) concentrations was observed. For the Clinton station, decreases in NOx and VOC levels d at the rate of 2.068 ± 0.032 ppb/yr and 14.637 ± 0.412 ppb C/yr, were not reflected in MDA8 ozone, which showed no discernable decrease over the 15 years. The regional transport of ozone plumes from the east and south-east directions of the Clinton station were identified as the likely factors for this pattern. Implications: The efficacy of emission control policies in the Houston-Galveston-Brazoria area can be evaluated by isolating the meteorological forcing from air quality time series data and developing long-term trends for ozone and precursor compounds. This paper applies the Kolmogorov–Zurbenko filter technique in combination with Multiple Linear Regression analysis to MDA8/MDA1 ozone, NOx, and VOC data between 2003-2017 at three air monitoring stations near the Houston Ship Channel. Estimates for trends of air quality are calculated and underlying causes are investigated to provide a guidance for further investigation into air quality management of the Greater Houston Area. [ABSTRACT FROM AUTHOR]

The Dallas-Fort Worth (DFW) area that experiences high temperature and intense solar radiation falls into the moderate nonattainment classification. The variation in meteorological parameters plays an important role in ambient ozone levels variation. Meteorological influences need to be decoupled from ozone data for long-term trend analysis. Temporal separation of maximum daily average 8-h ozone (MDA8 ozone), maximum daily temperature (TMAX), daily average solar radiation (DASR), and daily average wind speed (DAWS) were conducted using Kolmogorov-Zurbenko (KZ) filter for ozone records at Keller (C17), Arlington (C61), Red Bird (C402) monitoring stations in the DFW area from 2003 to 2017. Temporal separation, regression analysis, and meteorological detrending were performed. The long-term component had a clear and stable trend. The contribution of the long-term component to total variation was negligible, which is less than 2%. This is due to the removal of the data noise from the original time series data. The seasonal component had a major contribution (55% to 72%) in the total variation of the maximum temperature and solar radiation. However, the short-term component was dominant in the total variation of the MDA8 ozone (41–54%) and wind speed (68–79%). Regression analysis showed the baseline component bears the highest correlation than the short-term and raw. Solar radiation had the highest correlation to the MDA8 ozone, followed by temperature data in all three stations. Meteorological detrending showed the detrended long-term ozone had an increasing trend. The increasing trend was significant at C402 with a trend of 0.19 ± 0.006 ppb/y (0.398 R2), whereas slight increasing trends were found at C17 (0.072 ± 0.006 (0.107 R2)) and at C61 (0.019 ± 0.007 (0.005 R2)). The increasing trend of long-term components of MDA8 ozone was justified by the increasing level of NOx and VOCs from the mobile sources in the DFW area. [ABSTRACT FROM AUTHOR]