Browsing by Author "D.G. Kaskaoutis"

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Aerosol chemical characterization and role of carbonaceous aerosol on radiative effect over Varanasi in central Indo-Gangetic Plain
(Elsevier Ltd, 2016) S. Tiwari; U.C. Dumka; D.G. Kaskaoutis; Kirpa Ram; A.S. Panicker; M.K. Srivastava; Shani Tiwari; S.D. Attri; V.K. Soni; A.K. Pandey
This study investigates the chemical composition of PM10 aerosols at Varanasi, in the central Indo-Gangetic Plain (IGP) during April to July 2011, with emphasis on examining the contribution of elemental carbon (EC) to the estimates of direct aerosol radiative effect (DARE). PM10 samples are analysed for carbonaceous aerosols (Organic Carbon, OC and EC) and water-soluble ionic species (WSIS: Cl-, SO42-, NO3-, PO42- NH4+, Na+, K+, Mg2+ and Ca2+) and several diagnostic ratios (OC/EC, K+/EC, etc) have been also used for studying the aerosol sources at Varanasi. PM10 mass concentration varies between 53 and 310 μgm-3 (mean of 168 ± 73 μgm-3), which is much higher than the National and International air quality standards. The OC mass concentration varies from 6 μg m-3 to 24 μg m-3 (mean of 12 ± 5 μg m-3; 7% of PM10 mass), whereas EC ranges between 1.0 and 14.3 μg m-3 (4.4 ± 3.9 μg m-3; ~3% of PM10 mass). The relative low OC/EC of 3.9 ± 2.0 and strong correlation (R2 = 0.82) between them suggest the dominance of primary carbonaceous aerosols. The contribution of WSIS to PM10 is found to be ~12%, out of which ~57% and 43% are anions and cations, respectively. The composite DARE estimates via SBDART model reveal significant radiative effect and atmospheric heating rates (0.9-2.3 Kday-1). Although the EC contributes only ~3% to the PM10 mass, its contribution to the surface and atmospheric forcing is significantly high (37-63% and 54-77%, respectively), thus playing a major role in climate implications over Varanasi. © 2015 Elsevier Ltd.
Effects of crop residue burning on aerosol properties, plume characteristics, and long-range transport over northern India
(Wiley-Blackwell, 2014) D.G. Kaskaoutis; S. Kumar; D. Sharma; R.P. Singh; S.K. Kharol; M. Sharma; A.K. Singh; S. Singh; Atinderpal Singh; D. Singh
Aerosol emissions from biomass burning are of specific interest over the globe due to their strong radiative impacts and climate implications. The present study examines the impact of paddy crop residue burning over northern India during the postmonsoon (October-November) season of 2012 on modification of aerosol properties, as well as the long-range transport of smoke plumes, altitude characteristics, and affected areas via the synergy of ground-based measurements and satellite observations. During this period, Moderate Resolution Imaging Spectroradiometer (MODIS) images show a thick smoke/hazy aerosol layer below 2-2.5 km in the atmosphere covering nearly the whole Indo-Gangetic Plains (IGP). The air mass trajectories originating from the biomass-burning source region over Punjab at 500m reveal a potential aerosol transport pathway along the Ganges valley from west to east, resulting in a strong aerosol optical depth (AOD) gradient. Sometimes, depending upon the wind direction and meteorological conditions, the plumes also influence central India, the Arabian Sea, and the Bay of Bengal, thus contributing to Asian pollution outflow. The increased number of fire counts (Terra and Aqua MODIS data) is associated with severe aerosol-laden atmospheres (AOD500 nm>1.0) over six IGP locations, high values of Ångström exponent (>1.2), high particulate mass 2.5 (PM2.5) concentrations (>100-150 µgm-3), and enhanced Ozone Monitoring Instrument Aerosol Index gradient (~2.5) and NO2 concentrations (~6 × 1015mol/cm2), indicating the dominance of smoke aerosols from agricultural crop residue burning. The aerosol size distribution is shifted toward the fine-mode fraction, also exhibiting an increase in the radius of fine aerosols due to coagulation processes in a highly turbid environment. The spectral variation of the single-scattering albedo reveals enhanced dominance of moderately absorbing aerosols, while the aerosol properties, modification, and mixing atmospheric processes differentiate along the IGP sites depending on the distance from the aerosol source, urban influence, and local characteristics. © 2014. American Geophysical Union. All Rights Reserved.
Meteorological, atmospheric and climatic perturbations during major dust storms over Indo-Gangetic Basin
(Elsevier, 2015) Sarvan Kumar; Sanjay Kumar; D.G. Kaskaoutis; Ramesh P. Singh; Rajeev K. Singh; Amit K. Mishra; Manoj K. Srivastava; Abhay K. Singh
During the pre-monsoon season (April-June), the Indo-Gangetic Basin (IGB) suffers from frequent and intense dust storms originated from the arid and desert regions of southwest Asia (Iran, Afghanistan), Arabia and Thar desert blanketing IGB and Himalayan foothills. The present study examines the columnar and vertical aerosol characteristics and estimates the shortwave (0.25-4.0μm) aerosol radiative forcing (ARF) and atmospheric heating rates over Kanpur, central IGB, during three intense dust-storm events in the pre-monsoon season of 2010. MODIS images, meteorological and AERONET observations clearly show that all the dust storms either originated from the Thar desert or transported over, under favorable meteorological conditions (low pressure and strong surface winds) affecting nearly the whole IGB and modifying the aerosol loading and characteristics (Ångström exponent, single scattering albedo, size distribution and refractive index). CALIPSO observations reveal the presence of high-altitude (up to 3-5km) dust plumes that strongly modify the vertical aerosol profile and are transported over Himalayan foothills with serious climate implications (atmospheric warming, enhanced melting of glaciers). Shortwave ARF calculations over Kanpur using SBDART model show large negative forcing values at the surface (-93.27, -101.60 and -66.71Wm-2) during the intense dusty days, associated with planetary (top of atmosphere) cooling (-18.16, -40.95, -29.58Wm-2) and significant atmospheric heating (75.11, 60.65, 37.13Wm-2), which is translated to average heating rates of 1.57, 1.41 and 0.78Kday-1, respectively in the lower atmosphere (below ~3.5km). The ARF estimates are in satisfactory agreement with the AERONET ARF retrievals over Kanpur. © 2015 Elsevier B.V.
Scattering and absorption properties of near-surface aerosol over Gangetic-Himalayan region: The role of boundary-layer dynamics and long-range transport
(Copernicus GmbH, 2015) U.C. Dumka; D.G. Kaskaoutis; M.K. Srivastava; P.C.S. Devara
Light scattering and absorption properties of atmospheric aerosols are of vital importance for evaluating their types, sources and radiative forcing. This is of particular interest over the Gangetic-Himalayan (GH) region due to uplift of aerosol from the plains to the Himalayan range, causing serious effects on atmospheric heating, glaciology and monsoon circulation. In this respect, the Ganges Valley Aerosol Experiment (GVAX) was initiated in Nainital from June 2011 to March 2012 with the aim of examining the aerosol properties, source regions, uplift mechanisms and aerosol-radiation-cloud interactions. The present study examines the temporal (diurnal, monthly, seasonal) evolution of scattering (σsp) and absorption (σap) coefficients, their wavelength dependence, and the role of the Indo-Gangetic plains (IGP), boundary-layer dynamics (BLD) and long-range transport (LRT) in aerosol evolution via the Atmospheric Radiation Measurement Mobile Facility. The analysis is separated for particles 10μm and <1 μm in diameter in order to examine the influence of particle size on optical properties. The σsp and σap exhibit a pronounced seasonal variation between the monsoon low and post-monsoon (November) high, while the scattering wavelength exponent exhibits higher values during the monsoon, in contrast to the absorption Ångström exponent which maximizes in December-March. The elevated-background measuring site provides the advantage of examining the LRT of natural and anthropogenic aerosols from the IGP and southwest Asia and the role of BLD in the aerosol lifting processes. The results reveal higher aerosol concentrations at noontime along with an increase in mixing height, suggesting influence from IGP. The locally emitted aerosols present higher wavelength dependence of the absorption in October-March compared to the rather well-mixed and aged transported aerosols. Monsoon rainfall and seasonally changing air masses contribute to the alteration of the extensive and intensive aerosol properties.