Preprints
https://doi.org/10.5194/egusphere-2024-3093
https://doi.org/10.5194/egusphere-2024-3093
27 Nov 2024
 | 27 Nov 2024

Regional transport of aerosols from Northern India and its impact on boundary layer dynamics and air quality over Chennai, a coastal megacity in Southern India

Saleem Ali, Chandan Sarangi, and Sanjay Kumar Mehta

Abstract. Westerly driven regional transport of aerosols from the heavily polluted North India towards south-eastern India is a prevalent phenomenon during the winter season. Here, the regional aerosol transport events on the boundary layer dynamics and air quality over Chennai, a tropical South Asian megacity, are investigated. The long-term satellite data enables us to depict such regional transport events prolonged for a few days, accounting for ~10–13 per cent of the winter season. The occurrence of these regional transport events is increasing over time in southeastern India which are associated with relatively calmer conditions under anticyclonic wind circulation over north India extending to south India. The transported aerosol layer is generally located around ~1–3 km across the entire southeastern India, capped by the strong atmospheric temperature inversion. The regional aerosol/ haze transport significantly reduces the boundary layer height (ABL-H) by ~38 % compared to clear sky conditions ( ~2–2.5 km). Consequently, an increase in PM2.5 is observed to be ~30–35 % in association with the strong heating aloft ABL (~1.2–2.5 K), suppression of ABL-H and anticyclonic circulation over north India. This study provides robust observational evidence on the importance of regional transport of aerosols on air quality of downwind megacities and warrants more observational and modelling studies to constrain the inherent aerosol-induced effects on boundary layer dynamics.

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Journal article(s) based on this preprint

12 Aug 2025
Regional transport of aerosols from northern India and its impact on boundary layer height and air quality over Chennai, a coastal megacity in southern India
Saleem Ali, Chandan Sarangi, and Sanjay Kumar Mehta
Atmos. Chem. Phys., 25, 8769–8783, https://doi.org/10.5194/acp-25-8769-2025,https://doi.org/10.5194/acp-25-8769-2025, 2025
Short summary
Saleem Ali, Chandan Sarangi, and Sanjay Kumar Mehta

Interactive discussion

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • CC1: 'Comment on egusphere-2024-3093', Mukunda M Gogoi, 21 Dec 2024
  • RC1: 'Comment on egusphere-2024-3093', Anonymous Referee #2, 02 Jan 2025

Interactive discussion

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • CC1: 'Comment on egusphere-2024-3093', Mukunda M Gogoi, 21 Dec 2024
  • RC1: 'Comment on egusphere-2024-3093', Anonymous Referee #2, 02 Jan 2025

Peer review completion

AR: Author's response | RR: Referee report | ED: Editor decision | EF: Editorial file upload
AR by Saleem Ali on behalf of the Authors (16 Apr 2025)  Author's response   Author's tracked changes   Manuscript 
ED: Referee Nomination & Report Request started (25 Apr 2025) by Jayanarayanan Kuttippurath
RR by Anonymous Referee #1 (28 Apr 2025)
ED: Publish subject to technical corrections (24 May 2025) by Jayanarayanan Kuttippurath
AR by Saleem Ali on behalf of the Authors (27 May 2025)  Author's response   Manuscript 

Journal article(s) based on this preprint

12 Aug 2025
Regional transport of aerosols from northern India and its impact on boundary layer height and air quality over Chennai, a coastal megacity in southern India
Saleem Ali, Chandan Sarangi, and Sanjay Kumar Mehta
Atmos. Chem. Phys., 25, 8769–8783, https://doi.org/10.5194/acp-25-8769-2025,https://doi.org/10.5194/acp-25-8769-2025, 2025
Short summary
Saleem Ali, Chandan Sarangi, and Sanjay Kumar Mehta
Saleem Ali, Chandan Sarangi, and Sanjay Kumar Mehta

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Short summary
The pollutants over Northern India are transported towards South India under the influence of the prevalent wind system, especially during winter. This long-range transport induces a widespread haziness over southern India, lasting for days. We evaluated the occurrence of such transport episodes over south India using observational methods and found that it suppresses the boundary layer height by ~38 % compared to the clear days while exacerbating the surface pollution by ~30–35 %.
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