Skip to Content
Questions or Comments: amda@tceq.texas.gov

Texas Air Quality Modeling Results: Ozone Performance Statistics

Interactive chart, map, and data table of daily and monthly ozone (O3) performance statistics by ozone area and monitoring site, comparing the results of the TCEQ’s air quality modeling with surface observations.

Evaluating model performance determines how well it 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, 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)

An interactive chart and data table of ozone performance statistics of the TCEQ's 2019 photochemical modeling. Base case model results are compared with surface observations by episode at individual monitoring sites in the 4×4km-cell modeling domain (txs_4km).

The model performance statistics of various model efforts are discussed in Recommendations on Statistics and Benchmarks to Assess Photochemical Model Performance (Emery, et al, J&AWMA 67:5, 582-598, March 2017). The goal and criteria of ozone statistics presented in this study are available to overlay on the chart for the statistic metrics NME, NMB, and R2.

If you have any questions regarding this interactive chart, please send an email to amda@tceq.texas.gov with the subject "2019 Texas Photochemical Modeling Results - Daily Model Performance Statistics by Ozone Area".

Episode
Date		 Valid
Data		 Mo
ppb		 Mm
ppb		 MB
ppb		 ME
ppb		 RMSE
ppb		 NMB
%		 NME
%		 FB
%		 FE
%		 R2
 
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
choose ozone area
click a legend item to toggle the display of corresponding data series on the chart
click here to save chart image or data series
hold the left mouse button and select a rectangle in the chart area to zoom in
hover the cursor over chart to show the data values of a particular day
move the cursor into this label area, hold the left mouse button and move up or down to change the upper value; double-click to reset to a default value
similarly, change the bottom value here; the bottom value cannot be changed below zero
change date range by sliding the left and/or right handles on this navigation bar