Climate models generally underrepresent the warming by Central Africa biomass-burning aerosols over the Southeast Atlantic.
Marc Mallet, Pierre Nabat, Ben Johnson, Martine Michou, Jim Haywood, Cheng Chen, Оleg Dubovik
Abstract
<p>Recently, the South-East Atlantic region has been the focus of several field campaigns aimed at understanding the role of aerosols from biomass burning (BBA) in Central Africa between June and September on the radiative budget and climate in the tropics. Contrary to sulphate particles which scatter most of solar radiation, BBA have the particularity of absorbing a large proportion of it. However, these different campaigns, in agreement with recent space observations, have clearly highlighted the highly absorbing nature of these aerosols, which is stronger than previously thought. These optical properties are crucial for understanding the aerosol-radiation-cloud interactions and thus quantify the impact of these plumes on the climate of this region. This study shows that most of the latest generation global climate models that participated in the CMIP6 intercomparison exercise underestimate on average the absorption of solar radiation by BBA transported over the ocean. This bias, combined with recurrent model difficulties in representing marine stratocumulus over this region, leads many models to simulate a negative radiative forcing (cooling) at the top of the atmosphere, which is contrary to recent estimates. The magnitude of the solar warming induced by BBA is thus underestimated by these models, which could lead to an erroneous representation of the fast-response of low clouds and precipitation to the radiative forcing of these aerosols in the tropics.</p>