 |
| Titel |
Brown carbon aerosol in the North American continental troposphere: sources, abundance, and radiative forcing |
| VerfasserIn |
J. Liu, E. Scheuer, J. Dibb, G. S. Diskin, L. D. Ziemba, K. L. Thornhill, B. E. Anderson, A. Wisthaler, T. Mikoviny, J. J. Devi, M. Bergin, A. E. Perring, M. Z. Markovic, J. P. Schwarz, P. Campuzano-Jost, D. A. Day, J. L. Jimenez, R. J. Weber |
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| ISSN |
1680-7316
|
| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 15, no. 14 ; Nr. 15, no. 14 (2015-07-16), S.7841-7858 |
| Datensatznummer |
250119905
|
| Publikation (Nr.) |
 copernicus.org/acp-15-7841-2015.pdf |
|
|
|
|
|
| Zusammenfassung |
| Chemical components of organic aerosol (OA) selectively absorb light at short
wavelengths. In this study, the prevalence, sources, and optical importance
of this so-called brown carbon (BrC) aerosol component are investigated
throughout the North American continental tropospheric column during a
summer of extensive biomass burning. Spectrophotometric absorption
measurements on extracts of bulk aerosol samples collected from an aircraft
over the central USA were analyzed to directly quantify BrC abundance. BrC
was found to be prevalent throughout the 1 to 12 km altitude measurement
range, with dramatic enhancements in biomass-burning plumes. BrC to black carbon (BC) ratios, under background tropospheric conditions, increased with
altitude, consistent with a corresponding increase in the absorption Ångström exponent (AAE) determined from a three-wavelength particle soot absorption photometer (PSAP). The sum of inferred BC absorption and measured
BrC absorption at 365 nm was within 3 % of the measured PSAP absorption
for background conditions and 22 % for biomass burning. A radiative
transfer model showed that BrC absorption reduced top-of-atmosphere (TOA) aerosol
forcing by ~ 20 % in the background troposphere. Extensive
radiative model simulations applying this study background tropospheric
conditions provided a look-up chart for determining radiative forcing
efficiencies of BrC as a function of a surface-measured BrC : BC ratio and
single scattering albedo (SSA). The chart is a first attempt to provide a
tool for better assessment of brown carbon's forcing effect when one is
limited to only surface data. These results indicate that BrC is an
important contributor to direct aerosol radiative forcing. |
| |
|
| Teil von |
|
|
|
|
|
|
|
|