Time series of daily averaged NO_x and PM_2.5 at the Fresno Supersite along with the optimal multiple linear regression (MLR) models and model outliers. Crosses represent times with concentrations above the axis, circles are points rejected as outliers by the Iteratively Reweighted Least Squares (IRLS) algorithm. DOI: https://doi.org/10.1525/elementa.384.f1