a τa at 340 nm (purple) and 500 nm (green) as a function of temperature (T). Both daily (circle) and summer (square) medians are shown. Summer median τa are included only for years 2012, 2015, 2017, and 2018 due to data availability. b τa at 340 nm as a function of organic aerosol (OA) mass loading. Daily medians are shown with color indicating the year.