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| Titel |
Vertical profiling of methane and carbon dioxide using high resolution near-infrared heterodyne spectroscopic observations |
| VerfasserIn |
Alexander Rodin, Artem Klimchuk, Dmitry Churbanov, Anastasia Pereslavtseva, Maxim Spiridonov, Alexander Nadezhdinskyi |
| Konferenz |
EGU General Assembly 2014
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250097069
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| Publikation (Nr.) |
 EGU/EGU2014-12611.pdf |
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| Zusammenfassung |
| We present new method of monitoring greenhouse gases using spectroscopic observations of
solar radiation passed through the atmosphere with spectral resolution λvδλ up to 108. Such a
high resolution is achieved by heterodyne technique and allows to retrieve full information
about spectral line shape which, in turn, is used to distinguish contribution of different
atmospheric layers to the resulting absorption. Weak absorption line at 6056.5 cm-1 was
selected for CO2 measurements and a quartet of lines centered at 6057 cm-1for
CH4.
The instrument setup includes Sun tracker with a microtelescope and chopper, diode DFB
laser used as a local oscillator, a bundle of single mode optical fibers that provides medium
for radiation transfer and beam coupling, reference cell with depressurized methane for LO
frequency stabilization, and Fabry-Perot etalon for LO frequency calibration. A commercial
p-i-n diode with squared detector replaces a mixer and IF spectrometer, providing
measurement of heterodyne beating within a bandpass of few MHz, which determines the
effective spectral resolution of the instrument. Spectral coverage within narrow range (about
1 cm-1) is provided by ramping the LO frequency based on feedback from the reference
channel.
Observations of Sun in the Moscow region have resulted for the first time in
measurements of the atmospheric transmission near 1.65 μm with sub-Doppler spectral
resolution. In order to retrieve vertical profiles of methane and carbon dioxide we developed
the inversion algorithm implementing Tikhonov regularization approach. With measured
transmission having S/N ratio of 100 or higher, the uncertainty of CH4 profile is about 10
ppb, with the uncertainty of CO2 profile at 1 ppm. This techniques is promising an affordable
opportunity or widespread monitoring of greenhouse gases and may be implemented on
existing ground-based stations.
This work has been supported by the grant of Russian Ministry of education and science
#11.G34.31.0074 |
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