 |
| Titel |
Aerosol absorption and radiative forcing |
| VerfasserIn |
P. Stier, J. H. Seinfeld, S. Kinne, O. Boucher |
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| ISSN |
1680-7316
|
| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 7, no. 19 ; Nr. 7, no. 19 (2007-10-10), S.5237-5261 |
| Datensatznummer |
250005222
|
| Publikation (Nr.) |
 copernicus.org/acp-7-5237-2007.pdf |
|
|
|
|
|
| Zusammenfassung |
| We present a comprehensive examination of aerosol absorption with a focus on
evaluating the sensitivity of the global distribution of aerosol absorption
to key uncertainties in the process representation. For this purpose we
extended the comprehensive aerosol-climate model ECHAM5-HAM by effective
medium approximations for the calculation of aerosol effective refractive
indices, updated black carbon refractive indices, new cloud radiative
properties considering the effect of aerosol inclusions, as well as by
modules for the calculation of long-wave aerosol radiative properties and
instantaneous aerosol forcing. The evaluation of the simulated aerosol
absorption optical depth with the AERONET sun-photometer network shows a good
agreement in the large scale global patterns. On a regional basis it becomes
evident that the update of the BC refractive indices to Bond
and Bergstrom (2006) significantly improves the previous
underestimation of the aerosol absorption optical depth. In the global
annual-mean, absorption acts to reduce the short-wave anthropogenic aerosol
top-of-atmosphere (TOA) radiative forcing clear-sky from −0.79 to
−0.53 W m−2 (33%) and all-sky from −0.47 to
−0.13 W m−2 (72%). Our results confirm that basic assumptions about the BC
refractive index play a key role for aerosol absorption and radiative
forcing. The effect of the usage of more accurate effective medium
approximations is comparably small. We demonstrate that the diversity in the
AeroCom land-surface albedo fields contributes to the uncertainty in the
simulated anthropogenic aerosol radiative forcings: the usage of an upper
versus lower bound of the AeroCom land albedos introduces a global
annual-mean TOA forcing range of 0.19 W m−2 (36%) clear-sky and
of 0.12 W m−2 (92%) all-sky. The consideration of black carbon
inclusions on cloud radiative properties results in a small global
annual-mean all-sky absorption of 0.05 W m−2 and a positive TOA
forcing perturbation of 0.02 W m−2. The long-wave aerosol
radiative effects are small for anthropogenic aerosols but become of
relevance for the larger natural dust and sea-salt aerosols. |
| |
|
| Teil von |
|
|
|
|
|
|
|
|