Aerosol properties over the Indo-Gangetic Plain: A mesoscale perspective from the TIGERZ experiment

Abstract

[1] High aerosol loading over the northern Indian subcontinent can result in poor air quality leading to human health consequences and climate perturbations. The international 2008 TIGERZ experiment intensive operational period (IOP) was conducted in the Indo-Gangetic Plain (IGP) around the industrial city of Kanpur (26.51°N, 80.23°E), India, during the premonsoon (April-June). Aerosol Robotic Network (AERONET) Sun photometers performed frequent measurements of aerosol properties at temporary sites distributed within an area covering ∼50 km 2 around Kanpur to characterize pollution and dust in a region where complex aerosol mixtures and semi-bright surface effects complicate satellite retrieval algorithms. TIGERZ IOP Sun photometers quantified aerosol optical depth (AOD) increases up to ∼0.10 within and downwind of the city, with urban emissions accounting for ∼10-20% of the IGP aerosol loading on deployment days. TIGERZ IOP area-averaged volume size distribution and single scattering albedo retrievals indicated spatially homogeneous, uniformly sized, spectrally absorbing pollution and dust particles. Aerosol absorption and size relationships were used to categorize black carbon and dust as dominant absorbers and to identify a third category in which both black carbon and dust dominate absorption. Moderate Resolution Imaging Spectroradiometer (MODIS) AOD retrievals with the lowest quality assurance (QA ≥ 0) flags were biased high with respect to TIGERZ IOP area-averaged measurements. MODIS AOD retrievals with QA ≥ 0 had moderate correlation (R 2 = 0.52-0.69) with the Kanpur AERONET site, whereas retrievals with QA > 0 were limited in number. Mesoscale-distributed Sun photometers quantified temporal and spatial variability of aerosol properties, and these results were used to validate satellite retrievals.Citation: Giles, D. M., et al. (2011), Aerosol properties over the Indo-Gangetic Plain: A mesoscale perspective from the TIGERZ experiment,

Inferring aerosol types over the Indo-Gangetic Basin from ground based sunphotometer measurements

“…A recent study over the IGB region with the Aerosol Robotic Network (AERONET) data revealed significant gradient in various aerosol characteristics from central to the eastern sectors of the IGB during pre-monsoon period, which suggests diverse nature of aerosols and their effects over the region (Srivastava et al, 2011a). Mixing of natural dust with anthropogenic particles during this period, has been hypothesized in the IGB and corroborated with the AERONET data (Giles et al, 2011), further complicating the satellite retrieval of aerosol characteristics and quantifying the climatic effects (Mishra et al, 2010). Hence, it is important to understand the diurnal and spatial variability of aerosol types in the IGB to make realistic assessments of aerosol-hydroclimate interplay.…”

Aerosol optical properties and direct radiative forcing based on measurements from the China Aerosol Remote Sensing Network (CARSNET) in eastern China

“…It should also be mentioned that uncertainties in the AAE calculations due to uncertainties in the SSAs may have contributed to the observed differences between sites (Bergstrom et al, 2007;Giles et al, 2011). Ideally, the aerosol physical and chemical characteristic measurements will be combined at some point to more definitively classify the aerosol types.…”

“…Those sites typically have had high aerosol loadings and in many cases serious environmental problems (Cheng et al, 2015;Pan et al, 2010;Xia et al, 2013; L. C. ; H. Z. . Detailed information on aerosol optical depth (AOD), the types of aerosols and especially the size and absorption properties of ambient populations over a wide sampling of regions is needed to understand the effects of aerosols on the Earth's climate and the environment (Giles et al, 2011;Wang et al, 2010;. In particular, the aerosol direct radiative forcing is sensitive to the aerosol radiation absorptivity (Haywood and Shine, 1995).…”

Relating aerosol absorption due to soot, organic carbon, and dust to emission sources determined from in-situ chemical measurements

“…Russell et al (2010) highlighted that many recent studies have shown the persistent connections between aerosol absorbing species and the wavelength dependence of absorption. Thus, numerous studies have classified absorbing aerosol types from optical properties measured on ground stations (Eck et al, 1999;Dubovik et al, 2002;Collaud Coen et al, 2004;Fialho et al, 2005;Meloni et al, 2006;Kalapureddy et al, 2009;Mielonen et al, 2009;Giles et al, 2011Giles et al, , 2012 and from satellites (Higurashi and Nakajima, 2002;Barnaba and Gobbi, 2004;Jeong and Li, 2005;Kaufman et al, 2005;Torres et al, 2005;Kaskaoutis et al, 2007;Kim et al, 2007;Yu et al, 2009). In this study, in-situ optical properties and single particle chemical composition measured during three aircraft field campaigns are combined in order to validate a methodology for the estimation of absorbing aerosol types using spectral optical properties.…”