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| Titel |
Exploring the relation between aerosol optical depth and PM2.5 at Cabauw, the Netherlands |
| VerfasserIn |
M. Schaap, A. Apituley, R. M. A. Timmermans, R. B. A. Koelemeijer, G. Leeuw |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1680-7316
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 9, no. 3 ; Nr. 9, no. 3 (2009-02-05), S.909-925 |
| Datensatznummer |
250006819
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| Publikation (Nr.) |
 copernicus.org/acp-9-909-2009.pdf |
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| Zusammenfassung |
| Estimates of PM2.5 distributions based on satellite data depend critically
on an established relation between AOD and ground level PM2.5. In this study
we performed an experiment at Cabauw to establish a relation between AOD and
PM2.5 for the Netherlands. A first inspection of the AERONET L1.5 AOD and
PM2.5 data showed a low correlation between the two properties. The
AERONET L1.5 showed relatively many observations of high AOD values paired
to low PM2.5 values, which hinted cloud contamination. Various methods were
used to detect cloud contamination in the AERONET data to substantiate this
hypothesis. A cloud screening method based on backscatter LIDAR observations
was chosen to detect cloud contaminated observations in the AERONET L1.5
AOD. A later evaluation of AERONET L2.0 showed that the most data that are
excluded in the update from L1.5 to L2.0 were also excluded by our cloud
screening, which provides confidence in both our cloud-screening method as
well as the final screening in the AERONET procedure. The use of LIDAR
measurements in conjunction with the CIMEL AOD data is regarded highly
beneficial. Contra-intuitively, the AOD to PM2.5 relationship was shown to
be insensitive to inclusion of the mixed layer height. The robustness of the
relation improves dependent on the time window during the day towards noon.
The final relation found for Cabauw is PM2.5=124.5×AOD−0.34 and is
valid for fair weather conditions. The relationship found between bias
corrected MODIS AOD and PM2.5 at Cabauw is very similar to the analysis
based on the much larger dataset from ground based data only. We applied the
relationship to a MODIS composite map to assess the PM2.5 distribution over
the Netherlands for the first time. The verification of the derived map is
difficult because ground level artefact free PM2.5 data are lacking. The
validity and utility of our proposed mapping methodology should be further
investigated. |
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