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Texas Photochemical Modeling Results—Model Performance Statistics by Episode and Site

Interactive map and data table of model-performance statistics comparing results of the TCEQ’s air quality modeling with surface observations.

The purpose of evaluating model performance is to determine how well the model replicates an historical episode. Performance statistics do not feed directly into future ozone estimates or regulatory decisions.

To compare results of ozone photochemical modeling to actual observed data from surface monitoring sites, the TCEQ calculates the following statistical metrics, recommended by the EPA (Modeling Guidance for Demonstrating Attainment of Air Quality Goals for Ozone, PM2.5, and Regional Haze ):

  • Mo - Mean of Observed Values
  • Mm - Mean of Modeled Values (ideal if Mm = Mo)
  • MB - Mean Bias (mean difference; ideal value = 0)
  • ME - Mean Error (mean absolute difference; ideal value = 0)
  • RMSE - Root Mean Squared Error (ideal value = 0)
  • NMB - Normalized Mean Bias (relative mean difference; ideal value = 0)
  • NME - Normalized Mean Error (relative mean absolute difference; ideal value = 0)
  • FB - Fractional Bias (value range: -200% to 200%; ideal value = 0)
  • FE - Fractional Error (value range: 0 to 200%; ideal value = 0)
  • R2 - Coefficient of Determination (square of correlation coefficient; value range: 0 to 1; ideal value = 1)

This page shows an interactive map and data table of ozone performance statistics of the TCEQ's 2006 photochemical modeling. Base case model results are compared with surface observations by episode at individual monitoring sites in the 4×4km-cell modeling domain (tx_4km).

If you have any questions regarding this interactive map, please send an email to with the subject "Texas Photochemical Modeling Results - Model Performance Statistics by Episode and Site".

show instructions
Hide Map
Display Option
map color legend
model run name
Area Site Valid
select an episode
(loads new page)
select a model run
choose a data type
choose a statistic type
choose 2×2-cell bi-linear interpolated or cell value
choose hourly or eight-hour value
change marker size
change data range for marker colors
show/hide data value label on markers
show/hide map legend
display table data from sites of a selected area
export table data to a CSV file