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| Titel |
Greenhouse gas observations from Cabauw Tall Tower (1992–2010) |
| VerfasserIn |
A. T. Vermeulen, A. Hensen, M. E. Popa, W. C. M. Bulk, P. A. C. Jongejan |
| 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. 3 ; Nr. 4, no. 3 (2011-03-24), S.617-644 |
| Datensatznummer |
250001807
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| Publikation (Nr.) |
 copernicus.org/amt-4-617-2011.pdf |
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| Zusammenfassung |
Since 1992 semi-continuous in-situ observations of greenhouse gas
concentrations have been performed at the tall tower of Cabauw
(4.927° E, 51.971° N, −0.7 m a.s.l.). Through
1992 up to now, the measurement system has been gradually extended and
improved in precision, starting with CO2 and CH4
concentrations from 200 m a.g.l. in 1992 to vertical gradients at 4
levels of the gases CO2, CH4, SF6,
N2O, H2, CO and gradients at 2 levels for
222Rn. In this paper the measurement systems and measurement
results are described for the main greenhouse gases and CO, for the
whole period. The automatic measurement system now provides
half-hourly concentration gradients with a precision better than or
close to the WMO recommendations.
The observations at Cabauw show a complex pattern caused by the
influence of sources and sinks from a large area around the tower with
significant contributions of sources and sinks at distances up to
500–700 km. The concentration footprint area of Cabauw is one the
most intensive and complex source areas of greenhouse gases in the
world. Despite this, annual mean trends for the most important
greenhouse gases, compatible with the values derived using the
global network, can be reproduced from the measured concentrations at
Cabauw over the entire measurement period, with a measured increase in
the period 2000–2009 for CO2 of
1.90 ± 0.1 ppm yr−1, for CH4 of
4.4 ± 0.6 ppb yr−1, for N2O of
0.86 ± 0.04 ppb yr−1, and for SF6 of
0.27 ± 0.01 ppt yr−1; for CO no significant trend could be
detected.
The influences of strong local sources and sinks are reflected
in the amplitude of the mean
seasonal cycles observed at Cabauw, that are larger than the mean
Northern Hemisphere average; Cabauw mean seasonal amplitude for
CO2 is 25–30 ppm (higher value for lower
sampling levels). The observed CH4 seasonal amplitude is 50–110 ppb. All
gases except N2O show highest concentrations in winter and
lower concentrations in summer, N2O observations show two
additional concentration maxima in early summer and in autumn.
Seasonal cycles of the day-time mean concentrations show that surface
concentrations or high elevation concentrations alone do not give
a representative value for the boundary layer concentrations,
especially in winter time, but that the vertical profile data along
the mast can be used to construct a useful boundary layer mean
value. The variability at Cabauw in the atmospheric concentrations of
CO2 on time scales of minutes to hours is several ppm and is
much larger than the precision of the measurements (0.1 ppm). The
diurnal and synoptical variability of the concentrations at Cabauw
carry information on the sources and sinks in the footprint area of
the mast, that will be useful in combination with inverse
atmospheric transport model to verify emission estimates and improve
ecosystem models. For this purpose a network of tall tower stations
like Cabauw forms a very useful addition to the existing global observing
network for greenhouse gases. |
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