 |
| Titel |
High accuracy measurements of dry mole fractions of carbon dioxide and methane in humid air |
| VerfasserIn |
C. W. Rella, H. Chen, A. E. Andrews, A. Filges, C. Gerbig, J. Hatakka, A. Karion, N. L. Miles, S. J. Richardson, M. Steinbacher, C. Sweeney, B. Wastine, C. Zellweger |
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| ISSN |
1867-1381
|
| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Measurement Techniques ; 6, no. 3 ; Nr. 6, no. 3 (2013-03-27), S.837-860 |
| Datensatznummer |
250017852
|
| Publikation (Nr.) |
 copernicus.org/amt-6-837-2013.pdf |
|
|
|
|
|
| Zusammenfassung |
| Traditional techniques for measuring the mole fractions of greenhouse gases
in the well-mixed atmosphere have required dry sample gas streams (dew point
< −25 °C) to achieve the inter-laboratory compatibility
goals set forth by the Global Atmosphere Watch programme of the World
Meteorological Organisation (WMO/GAW) for carbon dioxide (±0.1 ppm in
the Northern Hemisphere and ±0.05 ppm in the Southern Hemisphere) and
methane (±2 ppb). Drying the sample gas to low levels of water vapour
can be expensive, time-consuming, and/or problematic, especially at remote
sites where access is difficult. Recent advances in optical measurement
techniques, in particular cavity ring down spectroscopy, have led to the
development of greenhouse gas analysers capable of simultaneous measurements
of carbon dioxide, methane and water vapour. Unlike many older technologies,
which can suffer from significant uncorrected interference from water vapour,
these instruments permit accurate and precise greenhouse gas measurements
that can meet the WMO/GAW inter-laboratory compatibility goals
(WMO, 2011a) without drying the sample gas. In
this paper, we present laboratory methodology for empirically deriving the
water vapour correction factors, and we summarise a series of in-situ
validation experiments comparing the measurements in humid gas streams to
well-characterised dry-gas measurements. By using the manufacturer-supplied
correction factors, the dry-mole fraction measurements have been
demonstrated to be well within the GAW compatibility goals up to a water
vapour concentration of at least 1%. By determining the correction factors
for individual instruments once at the start of life, this water vapour
concentration range can be extended to at least 2% over the life of the
instrument, and if the correction factors are determined periodically over
time, the evidence suggests that this range can be extended up to and even
above 4% water vapour concentrations. |
| |
|
| Teil von |
|
|
|
|
|
|
|
|