Preprints
https://doi.org/10.5194/gmd-2021-330
https://doi.org/10.5194/gmd-2021-330
Submitted as: model evaluation paper
03 Dec 2021
Submitted as: model evaluation paper | 03 Dec 2021
Status: this preprint is currently under review for the journal GMD.

Towards an improved representation of carbonaceous aerosols over the Indian monsoon region in a regional climate model RegCM4.6

Sudipta Ghosh1, Sagnik Dey1,2, Sushant Das3, Nicole Riemer4, Graziano Giuliani3, Dilip Ganguly1, Chandra Venkataraman5, Filippo Giorgi3, Sachchida Nand Tripathi6, Srikanthan Ramachandran7, Thazhathakal Ayyappen Rajesh7, Harish Gadhavi7, and Atul Kumar Srivastava8 Sudipta Ghosh et al.
  • 1Centre for Atmospheric Sciences, Indian Institute of Technology Delhi, India
  • 2Centre of Excellence for Research on Clean Air, Indian Institute of Technology Delhi, India
  • 3Earth System Physics Section, ICTP, Trieste, Italy
  • 4Department of Atmospheric Sciences, University of Illinois at Urbana-Champaign, IL, USA
  • 5Department of Chemical Engineering, Indian Institute of Technology Bombay, India
  • 6Department of Civil Engineering, Indian Institute of Technology Kanpur, India
  • 7Space and Atmospheric Sciences Division, Physical Research Laboratory, Ahmedabad, India
  • 8Indian Institute of Tropical Meteorology, New Delhi, India

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.

Sudipta Ghosh et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on gmd-2021-330', Anonymous Referee #1, 23 Feb 2022
  • RC2: 'Comment on gmd-2021-330', Anonymous Referee #2, 07 Mar 2022

Sudipta Ghosh et al.

Sudipta Ghosh et al.

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Short summary
Accurate representation of aerosols in climate models is critical in minimizing the uncertainty in climate projections. Here we implement region-specific emission fluxes and a more accurate scheme for carbonaceous aerosol ageing processes in a regional climate model, RegCM4, and show that it improves the model performance significantly against in-situ, reanalysis and satellite data over the Indian subcontinent. We recommend improving the model performance before using them for climate studies.