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| Titel |
Source brightness fluctuation correction of solar absorption fourier transform mid infrared spectra |
| VerfasserIn |
T. Ridder, T. Warneke, J. Notholt |
| 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 ; 4, no. 6 ; Nr. 4, no. 6 (2011-06-09), S.1045-1051 |
| Datensatznummer |
250002007
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| Publikation (Nr.) |
 copernicus.org/amt-4-1045-2011.pdf |
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| Zusammenfassung |
| The precision and accuracy of trace gas observations using solar absorption
Fourier Transform infrared spectrometry depend on the stability of the light
source. Fluctuations in the source brightness, however, cannot always be
avoided. Current correction schemes, which calculate a corrected interferogram
as the ratio of the raw DC interferogram and a smoothed DC interferogram, are
applicable only to near infrared measurements. Spectra in the mid infrared
spectral region below 2000 cm−1 are generally considered uncorrectable,
if they are measured with a MCT detector. Such measurements introduce an
unknown offset to MCT interferograms, which prevents the established source
brightness fluctuation correction. This problem can be overcome by a
determination of the offset using the modulation efficiency of the
instrument. With known modulation efficiency the offset can be calculated, and
the source brightness correction can be performed on the basis of
offset-corrected interferograms.
We present a source brightness fluctuation correction method which performs
the smoothing of the raw DC interferogram in the interferogram domain by an
application of a running mean instead of high-pass filtering the
corresponding spectrum after Fourier transformation of the raw DC
interferogram. This smoothing can be performed with the onboard software of
commercial instruments.
The improvement of MCT spectra and subsequent ozone profile and total column
retrievals is demonstrated. Application to InSb interferograms in the near
infrared spectral region proves the equivalence with the established
correction scheme. |
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