Example datasets for June 29, 2015. (a) Population-weighted percent of Facebook posters meeting criterion. White signifies regions with weighted population < 10. (b) 24-hour average surface PM2.5 concentrations from surface measurement sites. (c) Gridded hazard mapping system smoke product. .(d) Gridded, unfiltered MODIS Aqua and MODIS Terra aerosol optical depth. (e) WRFChem-simulated 24-hour average surface PM2.5 concentrations.