These boxes are stacked one on top of another and vary in height, with the layers of shorter boxes representing the parcels of air nearest the ground. First they select the area to be modeled or the modeling domain, and then they choose a time in the recent past when high ozone was measured over several days in the community, known as an ozone episode. Staff then collect data about the weather conditions and the known pollution emissions in the area at the time of the ozone episode. That data is used to run the model and see how well it simulates the ozone concentrations that were actually measured at each ozone monitor during each hour of the episode. A group of EPA-approved statistics and evaluation techniques are used to compare the model's output to the actual measured concentrations.
Staff use economic forecasts to estimate the future growth of industry, traffic, and population.
From these estimates they can forecast future air pollution emissions. They also adjust the emissions estimates to include the effect of existing state and federal regulations on cars and industry. If the existing regulations are not sufficient, the staff will work with the cities and industry to develop additional controls and test their effectiveness with the model. After being signed by the governor, the SIP is sent to the EPA and the air pollution control strategies it outlines are implemented by state law. This demonstration was required by the Federal Clean Air Act Amendments of 1990 for the El Paso area to avoid being reclassified to a more serious CO nonattainment status.