Brown carbon: a significant atmospheric absorber of solar radiation?
By Yan Feng, Veerabhadran Ramanathan, V. Kotamarthi. 2013
763 citations recorded by the source corpus.
Abstract. Several recent observational studies have shown organic carbon aerosols to be a significant source of absorption of solar radiation. The absorbing part of organic aerosols is referred to as "brown" carbon (BrC). Using a global chemical transport model and a radiative transfer model, we estimate for the first time the enhanced absorption of solar radiation due to BrC in a global model. The simulated wavelength dependence of aerosol absorption, as measured by the absorption Angstrom exponent (AAE), increases from 0.9 for non-absorbing organic carbon to 1.2 (1.0) for strongly (moderately) absorbing BrC. The calculated AAE for the strongly absorbing BrC agrees with AERONET spectral observations at 440–870 nm over most regions but overpredicts for the biomass burning-dominated South America and southern Africa, in which the inclusion of moderately absorbing BrC has better agreement. The resulting aerosol absorption optical depth increases by 18% (3%) at 550 nm and 56% (38%) at 380 nm for strongly (moderately) absorbing BrC. The global simulations suggest that the strongly absorbing BrC contributes up to +0.25 W m −2 or 19% of the absorption by anthropogenic aerosols, while 72% is attributed to black carbon, and 9% is due to sulfate and non-absorbing organic aerosols coated on black carbon. Like black carbon, the absorption of BrC (moderately to strongly) inserts a warming effect at the top of the atmosphere (TOA) (0.04 to 0.11 W m −2 ), while the effect at the surface is a reduction (−0.06 to −0.14 W m −2 ). Inclusion of the strongly absorption of BrC in our model causes the direct radiative forcing (global mean) of organic carbon aerosols at the TOA to change from cooling (−0.08 W m −2 ) to warming (+0.025 W m −2 ). Over source regions and above clouds, the absorption of BrC is higher and thus can play an important role in photochemistry and the hydrologic cycle.
Subfields: Atmospheric Science, Global and Planetary Change
View Paper: https://www.semanticscholar.org/paper/2fb518a9a9b291b108aae98468a5867fff3670ac
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Citations in the corpus
- Deriving brown carbon from multiwavelength absorption measurements: method and application to AERONET and Aethalometer observations (2016, background): “%) are likely to be biased slightly high (Feng et al., 2013; Lin et al., www.atmos-chem-phys.net/16/12733/2016/ Atmos.”
- Size-resolved measurements of brown carbon in water and methanol extracts and estimates of their contribution to ambient fine-particle light absorption (2013, background): “…have suggested brown carbon could affect the planetary radiation balance and climate by direct absorption (Ba-hadur et al., 2012; Chung et al., 2012; Feng et al., 2013; Park et al., 2010), or through dissolution into cloud droplets resulting in homogeneous absorbing droplets (Fuzzi et al., 2006).”