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Aerosol Characteristics over the Northwestern Indo-Gangetic Plain: Clear-sky Radiative Forcing of Composite and Black Carbon Aerosol

Category: Optical/Radiative Properties and Remote Sensing

Accepted Manuscripts
DOI: 10.4209/aaqr.2017.09.0339

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Onam Bansal1, Atinderpal Singh1,2, Darshan Singh 1

  • 1 Department of Physics, Punjabi University, Patiala, Punjab, India
  • 2 Geosciences Division, Physical Research Laboratory, Ahmedabad, Gujarat, India


Variability in PM, AOD and BC aerosol has been studied.
Source apportionment of BC aerosol.
Simulated optical and radiative properties of aerosol.
Radiative forcing of composite and black carbon aerosol.


The present study examines the aerosol characteristics over Patiala, northwestern India during October, 2013 to June, 2014. The average mass concentration of total suspended particulates (TSP) varied from 117 to 301 µg m–3 with PM10 accounts for ~63–83% to TSP during October to February (P1) while its fraction decreases and becomes less than ~40% during March to June (P2). Aerosol optical depth (AOD500) exhibited highest values during October (0.818) and lowest during April (0.332) along with wavelength dependence differing significantly on temporal scale. Ångstrom exponent (α380-870) values indicate relatively high amount of fine mode particles over study region during P1 as compared to P2, consistent with PM measurements. The monthly average mass concentration of climate forcing agent black carbon (BC) varied from 2.4 to 12 µg m–3 with highest mass concentration during December and lowest during June. Optical model derived monthly average single scattering albedo (SSA500) varied from 0.890 to 0.947 with relatively low values during P1 than P2. Radiative transfer model estimated monthly average atmospheric aerosol clear-sky direct radiative forcing (ATM ARF) ranged between +12 and +36 W m–2 over the study region. Even though, period averaged mass fraction of BC is only 2.4% to total mass of composite aerosol but its contribution to net ATM ARF is found to be significant (> 60%), indicating that BC contributes significantly to warming on regional scales. These results have implications to understand the impact of BC and composite aerosol on the Earth’s radiation budget and hence on the regional climate.


Biomass burning emission Particulates Aerosol optical depth Single scattering albedo Aerosol radiative forcin

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