Towards a stable and absolute atmospheric carbon dioxide instrument using spectroscopic null method

We present a novel spectral method to measure atmospheric carbon dioxide (CO2) with high precision and stability without resorting to calibration tanks during long-term operation. This spectral null method improves precision by reducing spectral proportional noise associated with laser emission inst...

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Bibliographic Details
Published in:Atmospheric measurement techniques 2013-07, Vol.6 (7), p.1611-1621
Main Authors: Xiang, B, Nelson, D. D, McManus, J. B, Zahniser, M. S, Wofsy, S. C
Format: Article
Language:English
Subjects:
Atmospheric carbon dioxide
Methods
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Summary:We present a novel spectral method to measure atmospheric carbon dioxide (CO2) with high precision and stability without resorting to calibration tanks during long-term operation. This spectral null method improves precision by reducing spectral proportional noise associated with laser emission instabilities. We employ sealed quartz cells with known CO2 column densities to serve as the permanent internal references in the null method, which improve the instrument's stability and accuracy. A prototype instrument – ABsolute Carbon dioxide (ABC) is developed using this new approach. The instrument has a one-second precision of 0.02 ppm, which averages down to 0.007 ppm within one minute. Long-term stability of within 0.1 ppm is achieved without any calibrations for over a one-month period. These results have the potential for eliminating the need for calibration cylinders for high accuracy field measurements of carbon dioxide.
ISSN:1867-8548
1867-1381
1867-8548
DOI:10.5194/amt-6-1611-2013