Abstract
Mitigation of carbonaceous aerosol emissions is expected to provide climate and health co-benefits. The accurate representation of carbonaceous aerosols in climate models is critical for reducing uncertainties in their climate feedbacks. In this regard, emission fluxes and aerosol life-cycle processes are the two primary sources of uncertainties. Here we demonstrate that incorporating a dynamic ageing scheme and emission estimates that are updated for the local sources improve the representation of carbonaceous aerosols over the Indian monsoon region in a regional climate model, RegCM, compared to its default configuration. The mean BC and OC surface concentrations in 2010 are estimated to be 4.25 and 10.35 μg m−3, respectively, over the Indo-Gangetic Plain (IGP), in the augmented model. The BC column burden over the polluted IGP is found to be 2.47 mg m−2, 69.95 % higher than in the default model configuration and much closer to available observations. The anthropogenic AOD increases by more than 19 % over the IGP due to the model enhancement, also leading to a better agreement with observed AOD. The top-of-the-atmosphere, surface, and atmospheric anthropogenic aerosol shortwave radiative forcing are estimated at −0.3, −9.3, and 9.0 W m−2, respectively, over the IGP and −0.89, −5.33, and 4.44 W m−2, respectively, over Peninsular India. Our results suggest that both the accurate estimates of emission fluxes and a better representation of aerosol processes are required to improve the aerosol life cycle representation in the climate model.
Highlights
Carbonaceous aerosols emitted from incomplete combustion constitute 20%-50% of the total global aerosol mass (Kanakidou et al., 2005; Putaud et al, 2010), causing substantial air quality degradation (Singh et al, 2021)
We examine the changes in carbonaceous aerosol burden and their impact on the radiation budget over the South Asia region due to the combined impact of the new dynamic ageing scheme and a regional emission inventory (Venkataraman et al, 2018) replacing the global emission inventory used in the default model version
Accurate estimates of emission fluxes and a better representation of aerosol processes are required to improve the representation of aerosol life-cycle and radiative effects in climate models
Summary
Carbonaceous aerosols (organic carbon, OC, and black carbon, BC) emitted from incomplete combustion constitute 20%-50% of the total global aerosol mass (Kanakidou et al., 2005; Putaud et al, 2010), causing substantial air quality degradation (Singh et al, 2021). Due to their ability to absorb solar radiation, carbonaceous aerosols contribute to global warming (Ramanathan and Carmichael, 2008). We examine the changes in carbonaceous aerosol burden and their impact on the radiation budget over the South Asia region due to the combined impact of the new dynamic ageing scheme and a regional emission inventory (Venkataraman et al, 2018) replacing the global emission inventory used in the default model version. We analyse and report the improvements in model performance due to the combined impact of incorporating a better emission inventory and a more realistic ageing scheme relative to the default model configuration and investigate these performance changes in terms of the aerosol processes considered in the model
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