Radiative absorption enhancements by black carbon controlled by particle-to-particle heterogeneity in composition

Laura Fierce, Timothy B. Onasch, Christopher D. Cappa, Claudio Mazzoleni, Swarup China, Janarjan Bhandari, Paul Davidovits, D. Al Fischer, Taylor Helgestad, Andrew T. Lambe, Arthur J. Sedlacek, Geoffrey D. Smith, Lindsay Wolff

Research output: Contribution to journalArticlepeer-review

106 Scopus citations

Abstract

Black carbon (BC) absorbs solar radiation, leading to a strong but uncertain warming effect on climate. A key challenge in modeling and quantifying BC’s radiative effect on climate is predicting enhancements in light absorption that result from internal mixing between BC and other aerosol components. Modeling and laboratory studies show that BC, when mixed with other aerosol components, absorbs more strongly than pure, uncoated BC; however, some ambient observations suggest more variable and weaker absorption enhancement. We show that the lower-than-expected enhancements in ambient measurements result from a combination of two factors. First, the often used spherical, concentric core-shell approximation generally overestimates the absorption by BC. Second, and more importantly, inadequate consideration of heterogeneity in particle-to-particle composition engenders substantial overestimation in absorption by the total particle population, with greater heterogeneity associated with larger model–measurement differences. We show that accounting for these two effects—variability in per-particle composition and deviations from the core-shell approximation—reconciles absorption enhancement predictions with laboratory and field observations and resolves the apparent discrepancy. Furthermore, our consistent model framework provides a path forward for improving predictions of BC’s radiative effect on climate.

Original languageEnglish (US)
Pages (from-to)5196-5203
Number of pages8
JournalProceedings of the National Academy of Sciences of the United States of America
Volume117
Issue number10
DOIs
StatePublished - Mar 10 2020
Externally publishedYes

Bibliographical note

Publisher Copyright:
© 2020 National Academy of Sciences. All rights reserved.

Keywords

  • Absorption enhancement
  • Aerosol mixing state
  • Black carbon
  • Direct radiative forcing

Fingerprint

Dive into the research topics of 'Radiative absorption enhancements by black carbon controlled by particle-to-particle heterogeneity in composition'. Together they form a unique fingerprint.

Cite this