On the attribution of black and brown carbon light absorption using the Ångström exponent
By D. Lack, J. Langridge. 2013
346 citations recorded by the source corpus.
Abstract. The absorption Angstrom exponent (AAE) of externally mixed black carbon (BCExt), or BC internally mixed with non-absorbing material (BCInt), is often used to determine the contribution of brown carbon (BrC) light absorption at short visible wavelengths. This attribution method contains assumptions with uncertainties that have not been formally assessed. We show that the potential range of AAE for BCExt (or BCInt) in the atmosphere can reasonably lead to +7% to −22% uncertainty in BCExt (or BCInt) absorption at short wavelengths derived from measurements made at longer wavelengths, where BrC is assumed not to absorb light. These uncertainties propagate to errors in the attributed absorption of BrC. For uncertainty in attributed BrC absorption to be ≤ ± 33%, 23% to 41% of total absorption must be sourced from BrC. These uncertainties would be larger if absorption by dust were also to be considered due to additional AAE assumptions. For data collected during a biomass-burning event, the mean difference between measured and AAE attributed BrC absorption was found to be 34% – an additional uncertainty in addition to the theoretical uncertainties presented. In light of the potential for introducing significant and poorly constrained errors, we caution against the universal application of the AAE method for attributing BrC absorption.
Subfields: Atmospheric Science, Health, Toxicology and Mutagenesis
View Paper: https://www.semanticscholar.org/paper/d56c6aa8771e74225a407f61facbdca5e41f80ed
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In Atmospheric Science
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Citations in the corpus
- Deriving brown carbon from multiwavelength absorption measurements: method and application to AERONET and Aethalometer observations (2016, methodology): “Many points fall within the shaded region, suggesting that the absorption for these sites at 440 nm is primarily from BC.”