Using High-Resolution Satellite Aerosol Optical Depth to Estimate Daily PM_2.5 Geographical Distribution in Mexico City

Recent advances in estimating fine particle (PM_2.5) ambient concentrations use daily satellite measurements of aerosol optical depth (AOD) for spatially and temporally resolved exposure estimates. Mexico City is a dense megacity that differs from other previously modeled regions in several ways: it has bright land surfaces, a distinctive climatological cycle, and an elevated semi-enclosed air basin with a unique planetary boundary layer dynamic. We extend our previous satellite methodology to the Mexico City area, a region with higher PM_2.5 than most U.S. and European urban areas. Using a novel 1 km resolution AOD product from the MODIS instrument, we constructed daily predictions across the greater Mexico City area for 2004-2014. We calibrated the association of AOD to PM_2.5 daily using municipal ground monitors, land use, and meteorological features. Predictions used spatial and temporal smoothing to estimate AOD when satellite data were missing. Our model performed well, resulting in an out-of-sample cross-validation R² of 0.724. Cross-validated root-mean-squared prediction error (RMSPE) of the model was 5.55 μg/m³. This novel model reconstructs long- and short-term spatially resolved exposure to PM_2.5 for epidemiological studies in Mexico City (Figure Presented).