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| Titel |
A broadband cavity ringdown spectrometer for in-situ measurements of atmospheric trace gases |
| VerfasserIn |
M. Bitter, S. M. Ball, I. M. Povey, R. L. Jones |
| 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. 9 ; Nr. 5, no. 9 (2005-09-23), S.2547-2560 |
| Datensatznummer |
250003075
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| Publikation (Nr.) |
 copernicus.org/acp-5-2547-2005.pdf |
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| Zusammenfassung |
| This paper describes a broadband cavity ringdown spectrometer and
its deployment during the 2002 North Atlantic Marine Boundary
Layer Experiment (NAMBLEX) to measure ambient concentrations of
NO3, N2O5, I2 and OIO at the Mace Head
Atmospheric Research Station, Co. Galway, Ireland. The effective
absorption path lengths accessible with the spectrometer generally
exceeded 10 km, enabling sensitive localised ``point" measurements
of atmospheric absorbers to be made adjacent to the other
instruments monitoring chemically related species at the same
site. For the majority of observations, the spectrometer was used
in an open path configuration thereby avoiding surface losses of
reactive species. A subset of observations targeted the
N2O5 molecule by detecting the additional NO3
formed by the thermal dissociation of N2O5. In all cases
the concentrations of the atmospheric absorbers were retrieved by
fitting the differential structure in the broadband cavity
ringdown spectra using a methodology adapted from long path
differential optical absorption spectroscopy. The uncertainty of
the retrieval depends crucially on the correct treatment and
fitting of the absorption bands due to water vapour, a topic that
is discussed in the context of analysing broadband cavity ringdown
spectra. The quality of the measurements and the retrieval method
are illustrated with representative spectra acquired during
NAMBLEX in spectral regions around 660 nm (NO3 and
N2O5) and 570 nm (I2 and OIO). Typical detection
limits were 1 pptv for NO3 in an integration time of 100 s, 4 pptv
for OIO and 20 pptv for I2 in an integration time of 10 min.
Additionally, the concentrations of atmospheric water
vapour and the aerosol optical extinction were retrieved in both
spectral regions. A companion paper in this issue presents the
time series of the measurements and discusses their significance
for understanding the variability of short lived nitrogen and
iodine compounds in the marine boundary layer. |
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