The Influence of Anomalous Biomass Emissions on ENSO in CESM2
The El Niño / Southern Oscillation (ENSO) is the dominant mode of interannual climate variability. Traditional descriptions of ENSO incorporate coupled interactions between the atmosphere and ocean but fail to incorporate feedbacks with terrestrial processes such as biomass burning emissions. In this work the influence on ENSO of observed anomalies in biomass burning emissions is explored using targeted ensembles of CESM2 in which background versus observed anomalous emissions are imposed.
The inter-ensemble differences reveal a subtle but important influence of biomass burning emissions in reduced ENSO biases in CESM2, characterized mainly by a decrease in La Niña intensity. In doing so, the emissions reduce CESM2 biases, including excessive ENSO power, diversity, and asymmetry. Biomass emissions over Indonesia are particularly sensitive to ENSO, and contributions from emissions in the Amazon and northern hemisphere extratropics also play a role in modifying aerosol burdens, clouds, and radiation. The analysis adds to recent work assessing the impacts of the 2019-2020 Australian wildfire season and underscores the importance of wildfire in seasonal climate prediction of ENSO.
The findings emphasize the importance of wildfire emissions in influencing clouds, radiation, and coupled dynamics and add to recent literature emphasizing a role for biomass burning emissions in ENSO phenomenology and seasonal climate prediction. The results point toward the importance of incorporating wildfire emissions in existing seasonal climate prediction efforts.