Figure 2. Daily cross-validation RMSE over year 2011 stratified by season.
Daily root mean squared error (“RMSE”) for PM2.5 concentration predictions in μg/m3 stratified by season. Results are displayed for four representative methods: Inverse Distance Weighting (“IDW”), Universal Kriging with CMAQ as only predictor (“UK”), the Downscaler model (“Down”) and Random Forest (“RF”). In each panel, the lines are loess smoothers.