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Atmospheric transport of black carbon (BC) aerosols over the Indo-Gangetic Plain

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Atmospheric transport of black carbon (BC) aerosols over the Indo-Gangetic Plain
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CC Attribution 3.0 Germany:
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Video to be uploaded for the paper entitled "Wintertime radiative effects of black carbon (BC) over Indo-Gangetic Plain as modelled with new BC emission inventories in CHIMERE". To reduce the uncertainty in the black carbon (BC) induced climatic impacts from the global and regional aerosol-climate model simulations, it is a foremost requirement to improve the prediction of modelled BC distribution. And that specifically, over the regions where the atmosphere is loaded with a large amount of BC, e.g., the Indo-Gangetic plain (IGP) in the Indian subcontinent. Here we present the wintertime radiative perturbation due to BC with an efficiently modelled BC distribution over the IGP in a high-resolution (0.1°×0.1°) chemical transport model, CHIMERE, implementing new BC emission inventories. The model efficiency in simulating the observed BC distribution was examined executing five simulations: Constrained and bottomup (Smog, Cmip, Edgar, Pku) implementing respectively, the recently estimated India-based constrained BC emission and the latest bottom-up BC emissions (India-based: Smog-India, and global: Coupled Model Intercomparison Project phase 6 (CMIP6), Emission Database for Global Atmospheric Research-V4 (EDGAR-V4) and Peking University BC Inventory (PKU)). A low estimated value of the normalised mean bias (NMB) and root mean square error (RMSE) from Constrained estimated BC concentration (NMB: < 17%) and aerosol optical depth due to BC (BC-AOD) (NMB: 11%) indicated that simulation with constrained BC emissions in CHIMERE could simulate the distribution of BC pollution over the IGP more efficiently than with the bottom-up. The large BC pollution covering the IGP region comprised of wintertime all-day (daytime) monthly mean BC concentration and BC-AOD from the Constrained, respectively, in the range 14–25 (6–8) µg m-3 and 0.04–0.08, with a strong correlation between the variance in BC emission and simulated BC mass concentration or BC-AOD. Five main hotspot locations were identified in and around Delhi (northern-IGP), Prayagraj (or Allahabad)-Varanasi (central-IGP), Patna-Palamu (upper/ lower mideastern-IGP), and Kolkata (eastern-IGP). The wintertime radiative perturbation due to BC aerosols from the Constrained included a wide-spread enhancement in atmospheric radiative warming by 2-3 times and a reduction in surface cooling by 10%-20%, with net warming at the top of atmosphere (TOA) of 10-15 W m-2, compared to the atmosphere without BC, for which, a net cooling at the TOA was, although, exhibited. These perturbations were spotted being the strongest around megacities (Kolkata and Delhi), and were inferred as 30%–50% lower from the bottomup than the Constrained.