Preprints
https://doi.org/10.5194/acp-2021-969
https://doi.org/10.5194/acp-2021-969

  01 Dec 2021

01 Dec 2021

Review status: this preprint is currently under review for the journal ACP.

Tropospheric warming over the North Indian Ocean caused by the South Asian anthropogenic aerosols: possible implications

Suvarna Fadnavis1, Prashant Chavan1, Akash Joshi2, Sunil Sonbawne1, Asutosh Acharya3, Panuganti Devara4, Alexandru Rap5, and Rolf Müller6 Suvarna Fadnavis et al.
  • 1Indian Institute of Tropical meteorology, MoES, Pune, India
  • 2Indian Institute of Technology, Kharagpur, India
  • 3Indian Institute of Technology, Bhubneshwar, India
  • 4Centre of Excellence in ACOAST/ACESH, Amity University Haryana (AUH), Gurugram 122413, India
  • 5School of Earth and Environment, University of Leeds, Leeds, United Kingdom
  • 6Forschungszentrum Jülich GmbH, IEK-7, Jülich, Germany

Abstract. Atmospheric concentrations of South Asian anthropogenic aerosols and their transport play a key role in the regional hydrological cycle. Here, we use the ECHAM6-HAMMOZ chemistry-climate model to show the structure and implications of the transport pathways of these aerosols during spring. Our simulations indicate that large amounts of anthropogenic aerosols are transported from South Asia to the North Indian Ocean (the Arabian Sea and North Bay of Bengal). These aerosols are then lifted into the upper troposphere and lower stratosphere (UTLS) by the convection over the Arabian Sea and Bay of Bengal. In the UTLS, they are further transported to the southern hemisphere (30–40° S) and downward into the troposphere by the secondary circulation induced by the aerosol changes. The carbonaceous aerosols are also transported to the Arctic and Antarctic producing local heating (0.002–0.05 K d−1).

The presence of anthropogenic aerosols causes negative radiative forcing (RF) at the TOA (0.90 ± 0.089 W m−2) and surface (−5.87 ± 0.31 W m−2) and atmospheric warming (+4.96 ± 0.24 W m−2) over South Asia (60° E–90° E, 8° N–23° N), except over the Indo-Gangetic plain (75° E–83° E, 23° N–30° N) where RF at the TOA is positive (+1.27 ± 0.16 W m−2) due to large concentrations of absorbing aerosols. The carbonaceous aerosols produced in-atmospheric heating along the aerosol column extending from the boundary layer to the UTLS (0.01 to 0.3 K d−1) and in the stratosphere globally (0.002 to 0.012 K d−1). The heating of the troposphere increases water vapor concentrations, which are then transported from the highly convective region (i.e. the Arabian Sea) to the UTLS (increasing water vapor by 0.02–0.06 ppmv).

Suvarna Fadnavis et al.

Status: open (until 02 Feb 2022)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on acp-2021-969', Anonymous Referee #1, 15 Dec 2021 reply

Suvarna Fadnavis et al.

Suvarna Fadnavis et al.

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Short summary
We show implications of the transport pathways of South Asian aerosols during spring. Our simulations show that large numbers of South Asian anthropogenic aerosols are transported to the North Indian Ocean in spring. These aerosols enhance tropospheric heating, evaporation, convection, and ascending winds over the Arabian Sea. These aerosols provide positive feedback leading to enhanced transport of aerosol and water vapor to the UTLS. In the stratosphere, water vapor are transported globally.
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