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| Titel |
Aerosol Optical Depth measurements at 340 nm with a Brewer spectrophotometer and comparison with Cimel sunphotometer observations at Uccle, Belgium |
| VerfasserIn |
V. Bock, H. Backer, A. Mangold, A. Delcloo |
| 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 ; 3, no. 6 ; Nr. 3, no. 6 (2010-11-19), S.1577-1588 |
| Datensatznummer |
250001361
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| Publikation (Nr.) |
 copernicus.org/amt-3-1577-2010.pdf |
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| Zusammenfassung |
| The Langley Plot Method (LPM) is adapted for the retrieval of Aerosol Optical
Depth (AOD) values at 340 nm from Brewer#178 sun scan measurements between
335 and 345 nm (convoluted with the band pass function of the Cimel
sunphotometer filter at 340 nm) performed in Uccle, Belgium. The use of sun
scans instead of direct sun measurements simplifies the comparison of the AOD
values with quasi-simultaneous Cimel sunphotometer values. Also, the
irradiance at 340 nm is larger than the one at 320.1 nm due to lower ozone
absorption, thus improving the signal to noise ratio. For the selection of
the cloudless days (from now on referred to as calibration quality clear
days), a new set of criteria is proposed. With the adapted method, individual
clear sky AOD values, for which the selection criteria are also presented in
this article, are calculated for a period from September 2006 until the end
of August 2010. These values are then compared to quasi-simultaneous Cimel
sunphotometer measurements, showing a very good agreement (the correlation
coefficient, the slope and the intercept of the regression line are
respectively 0.974, 0.968 and 0.011), which proves that good quality
observations can be obtained from Brewer sun scan measurements at 340 nm.
The analysis of the monthly and seasonal Brewer AODs at Uccle is consistent
with studies at other sites reporting on the seasonal variation of AODs in
Europe. The highest values can be observed in summer and spring, whereas more
than 50% of the winter AODs are lower than 0.3. On a monthly scale, the
lowest AOD are observed in December and the highest values occur in June and
April. No clear weekly cycle is observed for Uccle. The current
cloud-screening algorithm is still an issue, which means that some AOD values
can still be influenced by scattered clouds. This effect can be seen when
comparing the calculated monthly mean values of the Brewer with the AERONET
measurements. |
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