Changes in direct radiative effect of biogenic secondary organic aerosol from pre-industrial to present day

Abstract:

Biogenic secondary organic aerosol (BSOA), produced from atmospheric oxidation of biogenic volatile organic compounds, contributes a large fraction of fine particulate matter globally, and has significant implications for both air quality and climate. BSOA is not purely “natural”, as it can be modulated by anthropogenic emissions, including primary organic aerosol, nitrogen oxides (NO_x), and sulfur dioxide (SO₂). In this study, we implement a gas-aerosol BSOA scheme in a fully coupled chemistry-climate model (GFDL-AM4.1), including a 4-bin NO_x-dependent Volatility Basis Set for BSOA formation from monoterpenes, and aqueous-phase BSOA formation from isoprene oxidation products, including epoxydiols and glyoxal. We compare the performance of the model with the updated scheme and the default scheme (which applies fixed BSOA yields from isoprene and monoterpenes) by evaluating against long-term US-wide surface filter measurements and aircraft measurements in the southeast US and Amazon. We then use the updated AM4.1 to quantify the changes in direct radiative effect of BSOA from the preindustrial period to the present day, resulting from both changes in anthropogenic emissions and climate-induced changes in biogenic emissions. The impact of land use and land cover change is not considered. This work highlights the influence of anthropogenic activities on the climate system through biosphere-atmosphere interactions.