Long-term AOD-PM2.5 Relationship in Alaska during Summer Fire Season

Wildfire smoke contributes to the majority of summertime surface PM2.5 in Alaska. Due to lack of surface measurements, it remains unclear about the extent to which wildfire smoke is impacting surface air quality for the entire state. Here we establish linear regressions between daily averaged satellite aerosol optical depth (AOD) from Moderate Resolution Imaging Spectroradiometer (MODIS) onboard NASA Terra/Aqua satellites and daily averaged surface PM2.5 measurements from Alaska Department of Environmental Conservation (DEC) in central Alaska during season, for the past 20 years. We first evaluate MODIS AOD with 4 ground-based Aerosol Robotic Network (AERONET) measurements in central Alaska, and then compare the corrected MODIS AOD with DEC PM2.5 at Fairbanks, to establish separate relationships for clean days and smoky days. We use these relationships to derive daily average surface PM2.5 for the entire Alaska during the fire season of 2019 and compare that to the data collected by over 30 Purple Air low-cost sensors installed across Alaska. We find that the satellite derived PM2.5 is in good agreement with daily average Purple Air PM2.5 data, a new way to calibrate low-cost sensors in a regional network.