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| Titel |
Sensitivity of PARASOL multi-angle photopolarimetric aerosol retrievals to cloud contamination |
| VerfasserIn |
F. A. Stap, O. P. Hasekamp, T. Röckmann |
| 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 ; 8, no. 3 ; Nr. 8, no. 3 (2015-03-17), S.1287-1301 |
| Datensatznummer |
250116217
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| Publikation (Nr.) |
 copernicus.org/amt-8-1287-2015.pdf |
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| Zusammenfassung |
| An important problem in satellite remote sensing of aerosols is related to
the need to perform an adequate cloud screening. If a cloud screening is
applied that is not strict enough, the ground scene has the probability of
residual cloud cover which causes large errors on the retrieved aerosol
parameters. On the other hand, if the cloud-screening procedure is too
strict, too many clear sky cases, especially near-cloud scenes, will falsely
be flagged cloudy. The detrimental effects of cloud contamination as well as
the importance of aerosol cloud interactions that can be studied in these
near-cloud scenes call for new approaches to cloud screening. Multi-angle
multi-wavelength photopolarimetric measurements have a unique capability to
distinguish between scattering by (liquid) cloud droplets and aerosol
particles. In this paper the sensitivity of aerosol retrievals from
multi-angle photopolarimetric measurements to cloud contamination is
investigated and the ability to intrinsically filter the cloud-contaminated
scenes based on a goodness-of-fit criteria is evaluated. Hereto, an aerosol
retrieval algorithm is applied to a partially clouded over-ocean synthetic
data set as well as non-cloud-screened over-ocean POLDER-3/PARASOL
observations. It is found that a goodness-of-fit filter, together with
a filter on the coarse mode refractive index (mrcoarse
> 1.335) and a cirrus screening, adequately rejects the cloud-contaminated
scenes. No bias or larger SD are found in the retrieved parameters for this
intrinsic cloud filter compared to the parameters retrieved in a priori cloud-screened data set (using MODIS/AQUA cloud masks) of PARASOL observations.
Moreover, less high-aerosol load scenes are misinterpreted as cloud
contaminated. The retrieved aerosol optical thickness, single scattering
albedo and Ångström exponent show good agreement with AERONET
observations. Furthermore, the synthetic retrievals give confidence in the
ability of the algorithm to correctly retrieve the micro-physical aerosol
parameters. |
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