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Large contrast in the vertical distribution of aerosol optical properties and radiative effects across the Indo-Gangetic Plain during the SWAAMI-RAWEX campaign

Vaishya, Aditya and Babu, Surendran Nair Suresh and Jayachandran, Venugopalan and Gogoi, Mukunda M and Lakshmi, Naduparambil Bharathan and Moorthy, Krishnaswamy Krishna and Satheesh, Sreedharan Krishnakumari (2018) Large contrast in the vertical distribution of aerosol optical properties and radiative effects across the Indo-Gangetic Plain during the SWAAMI-RAWEX campaign. In: ATMOSPHERIC CHEMISTRY AND PHYSICS, 18 (23). pp. 17669-17685.

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Official URL: https://doi.org/10.1103/PhysRevD.98.092011

Abstract

Measurements of the vertical profiles of the optical properties ( namely the extinction coefficient and scattering and absorption coefficients respectively sigma(ext)=sigma(scat)=sigma(abs)) of aerosols have been made across the Indo-Gangetic Plain (IGP) using an instrumented aircraft operated from three base stations-Jodhpur (JDR), representing the semi-arid western IGP; Varanasi (VNS), the central IGP characterized by significant anthropogenic activities; and the industrialized coastal location in the eastern end of the IGP (Bhubaneswar, BBR)-just prior to the onset of the Indian summer monsoon. The vertical profiles depicted region-specific absorption characteristics, while the scattering characteristics remained fairly uniform across the region, leading to a west-east gradient in the vertical structure of single-scattering albedo (SSA). Integrated from near the ground to 3 km, the highest absorption coefficient and hence the lowest SSA occurred in the central IGP (Varanasi). Size distribution, inferred from the spectral variation of the scattering coefficient, showed a gradual shift from coarse-particle dominance in the western IGP to strong accumulation dominance in the eastern coast with the central IGP coming in between, arising from a change in the aerosol type from a predominantly natural (dust and sea salt) type in the western IGP to a highly anthropogenic type (industrial emissions, fossil fuel and biomass combustion) in the eastern IGP, with the central IGP exhibiting a mixture of both. Aerosol-induced short-wave radiative forcing, estimated using altitude-resolved SSA information, revealed significant atmospheric warming in the central IGP, while a top-of-atmosphere cooling is seen, in general, in the IGP. Atmospheric heating rate profiles, estimated using altitude-resolved SSA and column-averaged SSA, revealed considerable underestimation in the latter case, emphasizing the importance and necessity of having altitude-resolved SSA information as against a single value for the entire column.

Item Type: Journal Article
Additional Information: Copyright of this article belongs to COPERNICUS GESELLSCHAFT MBH
Department/Centre: Division of Mechanical Sciences > Centre for Atmospheric & Oceanic Sciences
Depositing User: Francis Jayakanth
Date Deposited: 10 Feb 2019 06:19
Last Modified: 10 Feb 2019 06:19
URI: http://eprints.iisc.ac.in/id/eprint/61350

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