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The southeastern Atlantic is home to an expansive smoke aerosol plume overlying a large cloud deck for approximately a third of the year. The aerosol plume is mainly attributed to the extensive biomass burning activities that occur in southern Africa. Current Earth system models (ESMs) reveal significant differences in their estimates of regional a...
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Context 1
... monthly mean full-column AOD for the five models in August 2017 is shown in Fig. 7. AODs over the southeastern Atlantic are larger in August 2017 than in September 2016, consistent with the satellite-derived above-cloud AOD in Fig. 1. Aerosol plumes are shifted northward in all the models relative to September 2016 because emissions are typically further north during the early part of the burning season ( Haywood et ...
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This study investigates long-term changes in the shortwave direct aerosol radiative effect (DARE) at the top of the atmosphere (TOA) induced by biomass burning aerosol (BBA) transported from southern Africa to the south-eastern Atlantic (SEA) stratocumulus region during extended fire seasons. The evolution since 2002 of aerosol, cloud properties, a...
Citations
... While most previous studies over the central African region often focus on assessing the simulated rainfall variability, they largely ignore the associated AEJ-S (e.g., Balas et al. 2007;Farnsworth et al. 2011). Similarly, most previous modeling studies focus on the radiative impacts of smoke aerosol over the southeast Atlantic and often ignore the dynamical mechanism responsible for the aerosol transport over the region (e.g., Sakaeda et al. 2011;Mallet et al. 2019;Chang et al. 2023). Here, we use observation and reanalysis datasets to assess whether CMIP6 models capture the climatological features of AEJ-S and its implication for aerosol, clouds, and precipitation distributions over the region. ...
Southern African easterly jet (AEJ-S) is an important mid-tropospheric feature critical to understanding the tropical convective system over central Africa and the aerosol-cloud interactions over the southeast Atlantic Ocean. However, it remains unclear how well models represent AEJ-S and its influence on aerosol transport, clouds, and precipitation distribution. Here, we use ground-and satellite-based observations and reanalysis datasets to assess the representation of AEJ-S in the Coupled Model Intercomparison Project Phase 6 (CMIP6) models between September and October during the peak of mid-tropospheric winds, aerosol transport, clouds, and precipitation. We find that most CMIP6 models have difficulty accurately simulating the strength, position, and spatial distribution of AEJ-S. Specifically, AEJ-S is relatively weaker and at a slightly lower altitude in the ensemble of CMIP6 models than represented by observation and reanalysis datasets. To assess the influence of the misrepresented AEJ-S on CMIP6-simulated aerosol, clouds, and precipitation distributions, we performed composite analyses using models with low and high biases based on the estimates of their mid-tropospheric easterly wind speed. We find that the misrepresentation of AEJ-S in CMIP6 models is associated with the overestimation of clouds and precipitation over central Africa, the underestimation of clouds over the southeast Atlantic Ocean, and the limitation of aerosol over the continent or deviation from the typical zonal aerosol transport over the Atlantic Ocean. Because aerosols, clouds, and precipitation are important components of the regional climate system, we conclude that accurate representation of AEJ-S is essential over central Africa and the southeast Atlantic Ocean.
