Tethered balloon-born and ground-based measurements of black carbon and particulate profiles within the lower troposphere during the foggy period in Delhi, India.
The ground and vertical profiles of particulate matter (PM) were mapped as part of a pilot study using a Tethered balloon within the lower troposphere (1000m) during the foggy episodes in the winter season of 2015-16 in New Delhi, India. Measurements of black carbon (BC) aerosol and PM <2.5 and 10μm (PM2.5& PM10respectively) concentrations and their associated particulate optical properties along with meteorological parameters were made. The mean concentrations of PM2.5, PM10, BC370nm,and BC880nmwere observed to be 146.8±42.1, 245.4±65.4, 30.3±12.2, and 24.1±10.3μgm-3, respectively. The mean value of PM2.5was ~12 times higher than the annual US-EPA air quality standard. The fraction of BC in PM2.5that contributed to absorption in the shorter visible wavelengths (BC370nm) was ~21%. Compared to clear days, the ground level mass concentrations of PM2.5and BC370nmparticles were substantially increased (59% and 24%, respectively) during the foggy episode. The aerosol light extinction coefficient (σext) value was much higher (mean: 610Mm-1) during the lower visibility (foggy) condition. Higher concentrations of PM2.5(89μgm-3) and longer visible wavelength absorbing BC880nm(25.7μgm-3) particles were observed up to 200m. The BC880nmand PM2.5aerosol concentrations near boundary layer (1km) were significantly higher (~1.9 and 12μgm-3), respectively. The BC (i.e BCtot) aerosol direct radiative forcing (DRF) values were estimated at the top of the atmosphere (TOA), surface (SFC), and atmosphere (ATM) and its resultant forcing were - 75.5Wm-2at SFC indicating the cooling effect at the surface. A positive value (20.9Wm-2) of BC aerosol DRF at TOA indicated the warming effect at the top of the atmosphere over the study region. The net DRF value due to BC aerosol was positive (96.4Wm-2) indicating a net warming effect in the atmosphere. The contribution of fossil and biomass fuels to the observed BC aerosol DRF values was ~78% and ~22%, respectively. The higher mean atmospheric heating rate (2.71Kday-1) by BC aerosol in the winter season would probably strengthen the temperature inversion leading to poor dispersion and affecting the formation of clouds. Serious detrimental impacts on regional climate due to the high concentrations of BC and PM (especially PM2.5) aerosol are likely based on this study and suggest the need for immediate, stringent measures to improve the regional air quality in the northern India.
Indian Institute of Tropical Meteorology, New Delhi Branch, New Delhi 110060, India.
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Bisht
Indian Institute of Tropical Meteorology, New Delhi Branch, New Delhi 110060, India. Electronic address: smbtiwari@tropmet.res.in.
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Tiwari
Aryabhatta Research Institute of Observational Sciences, Nainital 263001, India.
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Dumka
Indian Institute of Tropical Meteorology, New Delhi Branch, New Delhi 110060, India.
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Srivastava
Indian Institute of Tropical Meteorology, Pune 411008, India.
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Safai
Indian Institute of Tropical Meteorology, Pune 411008, India.
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Ghude
Indian Institute of Tropical Meteorology, Pune 411008, India.
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Chate
Indian Institute of Tropical Meteorology, Pune 411008, India.
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Rao
Indian Institute of Tropical Meteorology, Pune 411008, India.
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Ali
Indian Institute of Tropical Meteorology, Pune 411008, India.
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Prabhakaran
Indian Institute of Tropical Meteorology, Pune 411008, India.
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Panickar
Indian Metrological Department, Lodhi Road, New Delhi, India.
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Soni
Indian Metrological Department, Lodhi Road, New Delhi, India.
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Attri
Department of Environmental Science and Analytical Chemistry, Stockholm University, Stockholm SE-10691, Sweden.
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Tunved
Washington University in St Louis, St. Louis, MO 63130, USA.
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Chakrabarty
Clarkson University, Box 5708, Potsdam, NY 13699-5708, USA.
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Hopke
Anthropogenic; Biomass/biofuel; Black carbon; Climate change; Tethered balloon