 |
| Titel |
On the variability of the Ring effect in the near ultraviolet: understanding the role of aerosols and multiple scattering |
| VerfasserIn |
A. O. Langford, R. Schofield, J. S. Daniel, R. W. Portmann, M. L. Melamed, H. L. Miller, E. G. Dutton, S. Solomon |
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| ISSN |
1680-7316
|
| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 7, no. 3 ; Nr. 7, no. 3 (2007-01-31), S.575-586 |
| Datensatznummer |
250004548
|
| Publikation (Nr.) |
 copernicus.org/acp-7-575-2007.pdf |
|
|
|
|
|
| Zusammenfassung |
| The "filling-in" (FI) of Fraunhofer lines, often referred to as the Ring
effect, was examined using measurements of near ultraviolet sunlight
scattered from the zenith sky above Boulder, Colorado during July and August
2005. The FI of the 344.1 nm Fe I line was directly determined by comparing
direct sun and cloud-free zenith sky spectra recorded on the same day. The
results, obtained over solar zenith angles (SZA) from 20° to 70°,
are compared to the predictions of a simple rotational Raman Scattering
(RRS) spectral model. The measured FI was found to be up to 70% greater
than that predicted by first-order molecular scattering with a much stronger
SZA dependence. Simultaneously measured aerosol optical depths and Monte
Carlo calculations show that the combination of aerosol scattering and
second-order molecular scattering can account for these differences, and
potentially explain the contradictory SZA dependences in previously
published measurements of FI. These two scattering processes also introduce
a wavelength dependence to FI that complicates the fitting of diffuse
sunlight observations in differential optical absorption spectroscopy
(DOAS). A simple correction to improve DOAS retrievals by removing this
wavelength dependence is described. |
| |
|
| Teil von |
|
|
|
|
|
|
|
|