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| Titel |
A multi-year record of airborne CO2 observations in the US Southern Great Plains |
| VerfasserIn |
S. C. Biraud, M. S. Torn, J. R. Smith, C. Sweeney, W. J. Riley, P. P. Tans |
| 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 ; 6, no. 3 ; Nr. 6, no. 3 (2013-03-15), S.751-763 |
| Datensatznummer |
250017845
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| Publikation (Nr.) |
 copernicus.org/amt-6-751-2013.pdf |
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| Zusammenfassung |
| We report on 10 yr of airborne measurements of atmospheric CO2 mole
fraction from continuous and flask systems, collected between 2002 and 2012
over the Atmospheric Radiation Measurement Program Climate Research Facility
in the US Southern Great Plains (SGP). These observations were designed to
quantify trends and variability in atmospheric mole fraction of CO2 and
other greenhouse gases with the precision and accuracy needed to evaluate
ground-based and satellite-based column CO2 estimates, test forward and
inverse models, and help with the interpretation of ground-based CO2
mole-fraction measurements. During flights, we measured CO2 and
meteorological data continuously and collected flasks for a rich suite of
additional gases: CO2, CO, CH4, N2O, 13CO2,
carbonyl sulfide (COS), and trace hydrocarbon species. These measurements
were collected approximately twice per week by small aircraft (Cessna 172
initially, then Cessna 206) on a series of horizontal legs ranging in altitude
from 460 m to 5500 m a.m.s.l. Since the beginning of the program, more than
400 continuous CO2 vertical profiles have been collected (2007–2012),
along with about 330 profiles from NOAA/ESRL 12-flask (2006–2012) and 284
from NOAA/ESRL 2-flask (2002–2006) packages for carbon cycle gases and
isotopes. Averaged over the entire record, there were no systematic
differences between the continuous and flask CO2 observations when they
were sampling the same air, i.e., over the one-minute flask-sampling time.
Using multiple technologies (a flask sampler and two continuous analyzers),
we documented a mean difference of < 0.2 ppm between instruments.
However, flask data were not equivalent in all regards; horizontal
variability in CO2 mole fraction within the 5–10 min legs sometimes
resulted in significant differences between flask and continuous measurement
values for those legs, and the information contained in fine-scale
variability about atmospheric transport was not captured by flask-based
observations. The CO2 mole fraction trend at 3000 m a.m.s.l. was 1.91 ppm yr−1
between 2008 and 2010, very close to the concurrent trend at Mauna
Loa of 1.95 ppm yr−1. The seasonal amplitude of CO2 mole fraction
in the free troposphere (FT) was half that in the planetary boundary layer
(PBL) (~ 15 ppm vs. ~ 30 ppm) and twice that at
Mauna Loa (approximately 8 ppm). The CO2 horizontal variability was up
to 10 ppm in the PBL and less than 1 ppm at the top of the vertical profiles
in the FT. |
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