Towards a Satellite–In Situ Hybrid Estimate for Organic Aerosol Abundance

Organic aerosol (OA) is one of the main components of the global particulate burden and intimately links natural and anthropogenic emissions with air quality and climate. It is challenging to accurately represent OA in global models. Direct quantification of global OA abundance is not possible with current remote sensing technology; however, it may be possible to exploit correlations of OA with remotely observable quantities to infer OA spatiotemporal variability. In particular, formaldehyde (HCHO) and OA share common sources via both primary emissions and secondary production from oxidation of volatile organic compounds (VOCs). Here, we examine OA-HCHO correlations using data from summer-time airborne campaigns investigating biogenic (NASA SEAC⁴RS and DC3), biomass burning (NASA SEAC⁴RS) and anthropogenic conditions (NOAA CalNex and NASA KORUS-AQ). An estimate of near-surface OA is derived by the observed in situ relationships combining with HCHO column retrievals from NASA’s Ozone Monitoring Instrument (OMI). We evaluate this OA estimate against OA observations from the US EPA IMPROVE network, a global model, and surface aerosol extinction from Moderate Resolution Imaging Spectroradiometer (MODIS) aerosol optical depth (AOD). This novel method of estimating OA may enable new, spatially-resolved constraints on the global, or at least near the source regions, OA distributions.