A08: Influence of global wildfires on atmospheric chemistry

Influence of global wildfires on atmospheric chemistry:
model evaluation and preliminary results

@Li Xu

lxu16@uci.edu

@Qi Tang James T. Randerson (UCI)

Atmosphere

E3SM

Fire emissions influence tropospheric chemistry by emitting trace gases (e.g., CO, NMVOCs) and primary aerosols that, in turn, influence the oxidative capacity, radiation budget, and climate of the Earth System. In this work, we implemented a fire emissions simulation of trace gases and aerosol in the E3SM and the online chemistry module ChemUCI. We performed two 25-year simulations (with and without fires) during 1997-2021 to evaluate contemporary fire emissions on atmospheric chemistry constituents. The preliminary results show that the model is able to simulate atmospheric OH, CO, and O₃ concentration fairly well compared with peer studies and observations. Wildfires increase global average CO surface concentration by about 15% and tropospheric ozone burden by 5%, with a maximum increase of more than 20% over South Africa. OH increases near the surface in high-fire regions, likely due to interactions with fire-emitted NO, but decreases in remote regions of the atmosphere, likely as a consequence of the increasing CO burden. Fires also increase the accumulation mode aerosol burden by about 11%, averaged over the globe. Compared with E3SMv1, the most recent version of E3SM with coupled chemistry generates a smaller global cooling effect from fire impacts on atmospheric radiation.

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