Implications of particle composition and shape to dust radiative effect: A case study from the Great Indian Desert

Abstract

The assessment of direct radiative forcing (DRF) of aerosol is uncertain, particularly where the natural dust particles mix with the anthropogenic components. One of the sources of such uncertainty is the assumption of morphology (size and shape) and composition of pure dust particles. Recently Mishra and Tripathi [2008] have computationally assessed the effect of particle morphology on optical properties over the Great Indian Desert. As a continuation of the previous study, in this paper, we have further examined the effects on dust radiative properties. Non‐spherical pure dust particles show large variations in the optical and radiative properties from spherical pure dust particles, however, particle composition is found to have greater influence than particle shape on the radiative properties. Among the various shapes, sharp‐edged particles show larger difference than smooth‐shaped particles. Although the overall atmospheric absorption monotonically increases with increase in hematite content, maximum effect of particle non‐sphericity at 4% hematite content implies that non‐sphericity should be considered to minimize the uncertainty of regional estimates of aerosol DRF, as most of the global dusts contain that much hematite. However the difference in radiative properties for two different background dust cases due to particle morphology is low. Our results show that ignoring non‐sphericity will lead to under‐estimation of the regional warming and dust‐absorption efficiency.

Variability of Aerosol Parameters Derived from Ground and Satellite Measurements over Varanasi Located in the Indo-Gangetic Basin

“…IGB is bounded by Himalaya to the North, Vindyana -Satpura range to the south, Thar Desert and Arabian Sea in western part, while eastern part is surrounded by the Bay of Bengal. So IGB has a unique topography due to which natural and anthropogenic both aerosols show the strong seasonal variability (Massie et al, 2004;Singh et al, 2004;Dey and Tripathi, 2008;Misra et al, 2008;Srivastava et al, 2011;Kaskaoutis et al, 2012a). The IGB experiences four seasons annually, summer or pre-monsoon (March-June), monsoon (July-August), postmonsoon (September-October) and winter (NovemberFebruary).…”

Clear-sky direct aerosol radiative forcing variations over mega-city Delhi

“…Recently, Mishra et al (2008) have shown the effect of dust particle shape and composition on SSA in a case study from the Great Indian Desert. They have shown that SSA increases as the hematite content increases in dust.…”

Bulk Level to Individual Particle Level Chemical Composition of Atmospheric Dust Aerosols (PM5) over a Semi-Arid Urban Zone of Western India (Rajasthan)

“…As far as the Indian region is concerned, it has been shown that the chemical composition of mineral dust especially hematite fraction can significantly influence optical properties (such as single scattering albedo, asymmetry factor) by Mishra and Tripathi (2008a). Subsequently, Mishra et al (2008b) also assessed the effect of mineral dust particle composition and shape on radiative forcing of dust aerosols. Recently Mishra et al (2012) further studied effects of particle shape, hematite content and semi-external mixing with carbonaceous species.…”