Brown Carbon Aerosol
Dr. Chakrabarty's group was the one of the first to show that the smoldering phase of combustion, which emits 70% of total carbonaceous particles in the atmosphere from wildfires, produces primary light absorbing organic aerosol (a.k.a. tar balls). Over the years, his group has comprehensively characterized the spectral refractive indices, optical properties, and physicochemical properties of these aerosols emitted from different parts of the world (e.g., boreal, tropics). More recently, his group has shown that (i) the imaginary refractive index (corresponding to absorption) of these particles could be universally modeled using the classical Kramers-Kronig Dispersion relationship for a damped harmonic oscillator, and (ii) Atmospheric photo-oxidation (aging) of these aerosols bleach/diminishes their absorptive characteristics beyond 3.5 days of residence time.
Global Community Impact: The wealth of datasets generated on Brown Carbon microphysical and optical properties currently serve as “look up tables” for the satellite retrieval algorithm and climate modeling communities. For example, his brown carbon experimental datasets are currently being integrated in JPL’s Airborne Multiangle SpectroPolarimetric Imager’s (AirMSPI) retrieval algorithms. NASA’s OMI satellite is also in the process of incorporating carbon dataset into the latest version of their algorithm. Dr. Chakrabarty is working with the science team members of NASA’s Plankton, Aerosol, Clouds, ocean Ecosystem (PACE) mission for for application of his parameterizations in the PACE Ocean Color Instrument (OCI) and/or possibly a PACE Multi-Angle Polarimeter (MAP) for aerosol absorption characterization and correction. In addition, Geos-Chem and MOSAIC models are incorporating these datasets currently.
Chakrabarty, R. K., H. Moosmüller, L.-W. A. Chen, K. Lewis, W. P. Arnott, C. Mazzoleni, M. Dubey, C. E. Wold, W. M. Hao, and S. M. Kreidenweis (2010). “Brown Carbon in Tar Balls from Smoldering Biomass Combustion”. Atm. Chem. Phys., 10, 6363-6370.
Chakrabarty, R. K., S. Pervez, J.C. Chow, J. G. Watson, S. Dewangan, J. Robles, and G. Tian (2014). “Funeral Pyres in India: Brown Carbon Aerosol Emissions and Climate Impacts”. Environ. Sci. Technol. Letters, DOI: 10.1021/ez4000669.
Chakrabarty, R. K., M. Gyawali, R. L. N. Yatavelli, A. Pandey, A. C. Watts, J. Knue, L.-W. A. Chen, R. R. Pattison, A. Tsibart, V. Samburova, and H. Moosmüller (2016). Brown carbon aerosols from burning of boreal peatlands: microphysical properties, emission factors, and implications for direct radiative forcing, Atmos. Chem. Phys., 16 (5), 3033-3040.
Sumlin, B. J., A. Pandey, M. J. Walker, R. S. Pattison, B. J. Williams, and R. K. Chakrabarty (2017). Atmospheric Photooxidation Diminishes Light Absorption by Primary Brown Carbon Aerosol from Biomass Burning, Environmental Science & Technology Letters 4 (12), 540-545.
Sumlin B. J., Y. W. Heinson, R. Pattison, W. R. Heinson, W.M. Hao, and R. K. Chakrabarty (2018) UV–Vis–IR spectral complex refractive indices and optical properties of brown carbon aerosol from biomass burning, Journal of Quantitative Spectroscopy and Radiative Transfer 2018 206, 392-398.