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| Titel |
Critical surface albedo and its implications to aerosol remote sensing |
| VerfasserIn |
F. C. Seidel, C. Popp |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1867-1381
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Measurement Techniques ; 5, no. 7 ; Nr. 5, no. 7 (2012-07-17), S.1653-1665 |
| Datensatznummer |
250003006
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| Publikation (Nr.) |
 copernicus.org/amt-5-1653-2012.pdf |
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| Zusammenfassung |
| We analyse the critical surface albedo (CSA) and its implications to aerosol
remote sensing. CSA is defined as the surface albedo where the reflectance at
top-of-atmosphere (TOA) does not depend on aerosol optical depth (AOD). AOD
retrievals are therefore inaccurate at the CSA. The CSA is obtained by
derivatives of the TOA reflectance with respect to AOD using a radiative
transfer code. We present the CSA and the effect of surface albedo
uncertainties on AOD retrieval and atmospheric correction as a function of
aerosol single-scattering albedo, illumination and observation geometry,
wavelength and AOD. In general, increasing aerosol absorption and increasing
scattering angles lead to lower CSA. In contrast to the strict definition of
the CSA, we show that the CSA can also slightly depend on AOD and therefore
rather represent a small range of surface albedo values. This was often
neglected in previous studies. The following implications to aerosol remote
sensing applications were found: (i) surface albedo uncertainties result in
large AOD retrieval errors, particularly close to the CSA; (ii) AOD
retrievals of weakly or non-absorbing aerosols require dark surfaces, while
strongly absorbing aerosols can be retrieved more accurately over bright
surfaces; (iii) the CSA may help to estimate
aerosol absorption; and (iv) the presented sensitivity of the reflectance at
TOA to AOD provides error estimations to optimise AOD retrieval algorithms. |
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