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Comparison of 2000 Model-Predicted Concentrations to Monitored Data

As part of the 2002 National-Scale Air Toxics Assessment, EPA compared model-predicted ambient concentrations with available, but geographically limited, ambient air quality monitoring data for the years 2002 through 2005. For each monitor-pollutant combination, EPA compared the annual average concentration estimated by the ASPEN model at the exact geographical coordinates of the monitor location with the annual average monitored value to get a point-to-point comparison between the model and monitor concentrations. EPA used the same approach as that used for comparing the ASPEN model to monitor data for the 1999 national-scale assessment except that EPA used updated emissions, meteorological, and monitor input data for the 2002 assessment; there were no major changes to model formulation. For more details about the model to monitor analysis for the 2002 national-scale assessment, see file NATA 2002 Model to Monitor Comparison (PDF) (6pp, 182k).

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