 |
| Titel |
Aerosol retrieval experiments in the ESA Aerosol_cci project |
| VerfasserIn |
T. Holzer-Popp, G. Leeuw, J. Griesfeller, D. Martynenko, L. Klüser, S. Bevan, W. Davies, F. Ducos, J. L. Deuzé, R. G. Graigner, A. Heckel, W. Hoyningen-Hüne, P. Kolmonen, P. Litvinov, P. North, C. A. Poulsen, D. Ramon, R. Siddans, L. Sogacheva, D. Tanré, G. E. Thomas, M. Vountas, J. Descloitres, J. Griesfeller, S. Kinne, M. Schulz, S. Pinnock |
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| ISSN |
1867-1381
|
| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Measurement Techniques ; 6, no. 8 ; Nr. 6, no. 8 (2013-08-08), S.1919-1957 |
| Datensatznummer |
250085031
|
| Publikation (Nr.) |
 copernicus.org/amt-6-1919-2013.pdf |
|
|
|
|
|
| Zusammenfassung |
Within the ESA Climate Change Initiative (CCI) project
Aerosol_cci (2010–2013), algorithms for the production of
long-term total column aerosol optical depth (AOD) datasets from European
Earth Observation sensors are developed. Starting with eight existing
pre-cursor algorithms three analysis steps are conducted to improve and
qualify the algorithms: (1) a series of experiments applied to one month of
global data to understand several major sensitivities to assumptions needed
due to the ill-posed nature of the underlying inversion problem, (2) a round
robin exercise of "best" versions of each of these algorithms (defined
using the step 1 outcome) applied to four months of global data to identify
mature algorithms, and (3) a comprehensive validation exercise applied to
one complete year of global data produced by the algorithms selected as
mature based on the round robin exercise. The algorithms tested included
four using AATSR, three using MERIS and one using PARASOL.
This paper summarizes the first step. Three experiments were conducted to
assess the potential impact of major assumptions in the various aerosol
retrieval algorithms. In the first experiment a common set of four aerosol
components was used to provide all algorithms with the same assumptions. The
second experiment introduced an aerosol property climatology, derived from a
combination of model and sun photometer observations, as a priori
information in the retrievals on the occurrence of the common aerosol
components. The third experiment assessed the impact of using a common nadir
cloud mask for AATSR and MERIS algorithms in order to characterize the
sensitivity to remaining cloud contamination in the retrievals against the
baseline dataset versions. The impact of the algorithm changes was assessed
for one month (September 2008) of data: qualitatively by inspection of
monthly mean AOD maps and quantitatively by comparing daily gridded
satellite data against daily averaged AERONET sun photometer observations
for the different versions of each algorithm globally (land and coastal) and
for three regions with different aerosol regimes.
The analysis allowed for an assessment of sensitivities of all algorithms,
which helped define the best algorithm versions for the subsequent round
robin exercise; all algorithms (except for MERIS) showed some, in parts
significant, improvement. In particular, using common aerosol components and
partly also a priori aerosol-type climatology is beneficial. On the other
hand the use of an AATSR-based common cloud mask meant a clear improvement
(though with significant reduction of coverage) for the MERIS standard
product, but not for the algorithms using AATSR. It is noted that all these
observations are mostly consistent for all five analyses (global land, global
coastal, three regional), which can be understood well, since the set of
aerosol components defined in Sect. 3.1 was explicitly designed to cover
different global aerosol regimes (with low and high absorption fine mode, sea
salt and dust). |
| |
|
| Teil von |
|
|
|
|
|
|
|
|