The National Ambient Air Quality Standard (NAAQS) establishes thresholds for ground-level ozone composition which state governments are required to attain. Modeling of episodes in non-attainment of these standards is mandated so states can predict the effects of future emissions reductions to aid in their achieving the NAAQS. Novel statistical techniques, developed by our group, are used to analysis the data and to identify distinct, homogeneous groups of episodes.

The purpose of the current research is to determine ozone episodes in the Houston, Texas area with similar spatial features. The hourly ozone composition time series measurements are obtained from AIRS operated by the Texas Commission for Environmental Quality, collected from a network of 20 monitoring stations positioned in and around the Houston, Texas Metropolitan Statistical Area. Houston is representative of a large “Ozone influence regime” comprising much of the southeastern United States. The Atlantic Ocean lies to the east and it is proximate to the Gulf of Mexico coast. The “petrochemical corridor” responsible for the major emission sources stretches from southeastern Texas to southwestern Louisiana.