A New Classification of Aerosol Sources and Types as Measured over Jaipur, India

Abstract

The aerosol properties retrieved from the AErosol RObotic NETwork (AERONET) measurements during the period 2009 to 2012 over Jaipur (26.9°N, 75.8°E, 450m asl) in Northwestern India are used for the first time to identify the types of aerosols. In order to consider the appropriate threshold of aerosol optical thickness (τ) at 500 nm (τ 500 ) and Angstrom exponent (α) in the spectral band 440-870 nm, a novel approach has been conducted and applied for the identification process. Five prevailing aerosol classes are identified: desert dust, biomass, maritime, arid background and mixed aerosols. Arid background and desert dust type aerosols are the most common at Jaipur (34.7% and 13.6%, respectively), with a wide variability in both τ and α. In about 8.4% of the cases, aerosols can be classified as maritime, although mixing with other aerosols (33.6%) is substantial. The ground-based spectral optical thickness and the refractive index estimated at visible and near-infrared wavelengths are used to account for the type of atmospheric aerosols. They are compared with four more AERONET sites located in India based upon their geographical distribution and extensive data availability. Simultaneously, single scattering albedo of dust is also inferred for all the available AERONET sites for the same period over India. The comparison results suggest that Jaipur arid background is more scattering in nature than Northern and Western regions in India. Finally, the absorption is less in summer than in winter over the Jaipur site.

Mass concentration, optical depth and carbon composition of particulate matter in the major southern West African cities of Cotonou (Benin) and Abidjan (Côte d'Ivoire)

“…However, it can explain the fact that less measurements are available during the wet season for Abidjan than Cotonou because of cloud cover. The W season shows the lowest Ångström exponent value and low AOD, which reflects the contribution of maritime aerosols (Kaskaoutis et al, 2009;Verma et al, 2015;Toledano et al, 2007). Figure 7 shows that during the largest peak values (above 100 µg m −3 ) in the dry season, D1 and D2 are associated with an Ångström exponent close to 0.5, which means that advected dust might sporadically contribute to the increase in the ground-level PM 2.5 concentration.…”

“…Following Kaufman et al (2000), large particles (dust or maritime aerosols) are dominant in the size distribution when the Ångström coefficient is below 0.7, although Toledano et al (2007) have reported a threshold of 1.05. A low value, typically below 0.8, of the Ångström exponent associated with high AOD, typically above 0.6 (Verma et al, 2015), indicates a significant contribution of coarse dust-like particles to the AOD (Balarabe et al, 2016).…”

“…W1 and W2, the long rainy seasons; D1 and D2 , the short dry seasons; W1 and W2 ; the short rainy seasons; and D1 and D2, the long dry seasons for all the study period. the impact of mineral dust on the atmospheric column during the Harmattan as mineral dust transport is associated with high AOD and a low Ångström exponent (Toledano et al, 2007;Verma et al, 2015). The increase in the Ångström exponent during the long wet season (W) tends to be correlated with the start of the 27.5 ± 6 17 ± 4 10 ± 3 6.5 ± 1 2.0 ± 1.0 55 ± 30 D 16 18.5 ± 2 12 ± 1 8 ± 1 4.5 ± 1 2.0 ± 0.6 62 ± 20 W 18 40 ± 11 19.5 ± 3 11.5 ± 1 7.5 ± 2 1.7 ± 0.7 133 ± 50 D 31 52 ± 22 28.5 ± 5 20 ± 7 8.5 ± 2 2.5 ± 1.0 74 ± 54…”

Spatiotemporal characteristics of aerosols in India: Observations and model simulations

“…The two locations, Ahmedabad and Jaipur in the western expanse of IGP exhibit differences in terms of aerosol type and the values. AODs are higher over Jaipur (Verma et al, 2015) when compared to Ahmedabad . The arid background aerosols are predominant over Jaipur, .…”

“…The arid background aerosols are predominant over Jaipur, . Single scattering albedo was found to be higher over Jaipur indicating that the aerosols over Jaipur are more scattering in nature (Verma et al, 2015), while the aerosols are more absorbing in nature over Ahmedabad . Similarly, the locations in the north/northeastern IGP, namely, Kanpur and Gandhi College show prominent spatial variations in terms of aerosol characteristics, sources and types (Kedia et al, 2014).…”