Variability in Air Quality Exceedances and Large-Scale Meteorology in the Southeastern Texas Region

This study examines the relationship between large-scale meteorological patterns and air quality in the Houston metropolitan area over a ten-year period. We use a meteorological regime classification applying a Self-Organizing Map (SOM) approach to 700 mb geopotential height anomalies from reanalysis output for 10 years of summer months defining 16 distinct nodes which are collected into four main regimes: (1) pre-trough, (2) post-trough, (3) anticyclonic and (4) transitional. Hourly air quality measurements of particulate matter (PM_2.5) and ozone concentrations (O₃) from a sensor network operated by the Texas Commission on Environmental Quality (TCEQ) are mapped onto these weather regimes. Preliminary results show distinct differences in the distributions of maximum PM_2.5 and O₃ concentration values and their correlations with inter-regime differences being more prominent for days with the highest ozone concentrations. We use the U.S. Environmental Protection Agency's (EPA) standards to define elevated levels: above 70 parts per billion (ppb) for O₃ and above 35 micrograms per cubic meter (µg m^-3) for PM_2.5. O₃ levels change noticeably between weather regimes, with the highest levels observed during post-trough conditions. We find that daily maximum O₃ and PM_2.5 levels are weakly correlated, with the strongest relationship occurring in later summer months (August and September). Ongoing analysis investigates the geographical variability in air quality exceedances within each meteorological regime towards disentangling the contributions from local and larger-scale processes. Our findings can help improve air quality management strategies for the Southeastern Texas region.