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Importance of aerosol non-sphericity in estimating aerosol radiative forcing in Indo-Gangetic Basin

Srivastava, P and Dey, S and Srivastava, AK and Singh, S and Mishra, SK and Tiwari, S (2017) Importance of aerosol non-sphericity in estimating aerosol radiative forcing in Indo-Gangetic Basin. Science of the Total Environment, 599 (1). pp. 655-662.

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Aerosols are usually presumed spherical in shape while estimating the direct radiative forcing (DRF) using observations or in the models. In the Indo-Gangetic Basin (IGB), a regional aerosol hotspot where dust is a major aerosol species and has been observed to be non-spherical in shape, it is important to test the validity of this assumption. We address this issue using measured chemical composition at megacity Delhi, a representative site of the western IGB. Based on the observation, we choose three non-spherical shapes - spheroid, cylinder and chebyshev, and compute their optical properties. Non-spherical dust enhances aerosol extinction coefficient (βext) and single scattering albedo (SSA) at visible wavelengths by > 0.05 km− 1 and > 0.04 respectively, while it decreases asymmetry parameter (g) by ~ 0.1. Accounting non-sphericity leads top-of-the-atmosphere (TOA) dust DRF to more cooling due to enhanced backscattering and increases surface dimming due to enhanced βext. Outgoing shortwave flux at TOA increases by up to 3.3% for composite aerosols with non-spherical dust externally mixed with other spherical species. Our results show that while non-sphericity needs to be accounted for, choice of shape may not be important in estimating aerosol DRF in the IGB.

Item Type: Article
Additional Information: Copyright of this article belongs to Elsevier
Subjects: Meteorology and Climatology
Depositing User: IITM Library
Date Deposited: 13 Aug 2018 09:10
Last Modified: 13 Aug 2018 09:10

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