Comparison of total (primary plus secondary) area-weighted (black dots) and population-weighted (blue triangles) annual average predicted PM_2.5 concentration change for WRF-Chem (<i>x</i> axis) and either InMAP or COBRA (<i>y</i> axis) for 11 emissions scenarios.

<p>To assist in comparison between area- and population-weighted predictions, concentrations shown here are normalized so that the largest value in each comparison equals one. The gray lines represent 1 : 1, 2 : 1, and 1 : 2 ratios between the models, and the black and blue lines represent least-squares regressions. Performance statistics for each comparison are listed below the plots. Abbreviations: MFB = mean fractional bias; MFE = mean fractional error; MR = model ratio; <i>R</i>² = squared Pearson correlation coefficient; <i>S</i> = slope of regression line.