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| Titel |
Stratospheric and tropospheric NO2 variability on the diurnal and annual scale: a combined retrieval from ENVISAT/SCIAMACHY and solar FTIR at the Permanent Ground-Truthing Facility Zugspitze/Garmisch |
| VerfasserIn |
R. Sussmann, W. Stremme, J. P. Burrows, A. Richter, W. Seiler, M. Rettinger |
| 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 ; 5, no. 10 ; Nr. 5, no. 10 (2005-10-07), S.2657-2677 |
| Datensatznummer |
250003099
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| Publikation (Nr.) |
 copernicus.org/acp-5-2657-2005.pdf |
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| Zusammenfassung |
| Columnar NO2 retrievals from solar FTIR measurements at the Zugspitze
(47.42° N, 10.98° E, 2964 m a.s.l.), Germany were investigated
synergistically with columnar NO2 retrieved from SCIAMACHY data by the
University of Bremen scientific algorithm UB1.5 for the time span July 2002-October
2004. A new concept to match FTIR data to the time of satellite
overpass makes use of the NO2 daytime increasing rate retrieved from
the FTIR data set itself [+1.02(6)E+14 cm-2/h]. This measured increasing
rate shows no significant seasonal variation. SCIAMACHY data within a 200-km
radius around Zugspitze were considered, and a pollution-clearing
scheme was developed to select only pixels corresponding to clean background
(free) tropospheric conditions, and exclude local pollution hot spots. The resulting
difference between SCIAMACHY and FTIR columns (without correcting
for the different sensitivities of the instruments) varies between
0.60-1.24E+15 cm-2 with an average of 0.83E+15 cm-2. A
day-to-day scatter of daily means of ≈7-10% could be retrieved in mutual
agreement from FTIR and SCIAMACHY. Both data sets are showing sufficient
precisions to make this assessment. Analysis of the averaging kernels gives
proof that at high-mountain-site FTIR is a highly accurate measure for the pure
stratospheric column, while SCIAMACHY shows significant tropospheric
sensitivity. Based on this finding, we set up a combined a posteriori
FTIR-SCIAMACHY retrieval for tropospheric NO2, based upon the averaging
kernels. It yields an annual cycle of the clean background (free)
tropospheric column (<10 km) with variations between 0.75-1.54E+15 cm-2,
an average of 1.09E+15 cm-2, and an intermediate phase
between that of the well known boundary layer and stratospheric annual
cycles. The outcome is a concept for an integrated global observing system
for tropospheric NO2 that comprises DOAS nadir satellite measurements
and a set of latitudinally distributed mountain-site or clean-air FTIR
stations. |
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