 |
| Titel |
Variability and budget of CO2 in Europe: analysis of the CAATER airborne campaigns – Part 1: Observed variability |
| VerfasserIn |
I. Xueref-Remy, C. Messager, D. Filippi, M. Pastel, P. Nédélec, M. Ramonet, J. D. Paris, P. Ciais |
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| ISSN |
1680-7316
|
| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 11, no. 12 ; Nr. 11, no. 12 (2011-06-20), S.5655-5672 |
| Datensatznummer |
250009851
|
| Publikation (Nr.) |
 copernicus.org/acp-11-5655-2011.pdf |
|
|
|
|
|
| Zusammenfassung |
| Atmospheric airborne measurements of CO2 are very well suited for
estimating the time-varying distribution of carbon sources and sinks at the
regional scale due to the large geographical area covered over a short time.
We present here an analysis of two cross-European airborne campaigns carried
out on 23–26 May 2001 (CAATER-1) and 2–3 October 2002 (CAATER-2) over
Western Europe. The area covered during CAATER-1 and CAATER-2 was 4° W to
14° E long; 44° N to 52° N lat and 1° E to
17° E long; 46° N to 52° N lat respectively. High precision in situ CO2, CO and Radon 222
measurements were recorded. Flask samples were collected during both
campaigns to cross-validate the in situ data. During CAATER-1 and CAATER-2, the
mean CO2 concentration was 370.1 ± 4.0 (1-σ standard
deviation) ppm and 371.7 ± 5.0 (1-σ) ppm respectively. A HYSPLIT
back-trajectories analysis shows that during CAATER 1, northwesterly winds
prevailed. In the planetary boundary layer (PBL) air masses became
contaminated over Benelux and Western Germany by emissions from these highly
urbanized areas, reaching about 380 ppm. Air masses passing over rural areas
were depleted in CO2 because of the photosynthesis activity of the
vegetation, with observations as low as 355 ppm. During CAATER-2, the
back-trajectory analysis showed that air masses were distributed among the 4
sectors. Air masses were enriched in CO2 and CO over anthropogenic
emission spots in Germany but also in Poland, as these countries have part
of the most CO2-emitting coal-based plants in Europe. Simultaneous
measurements of in situ CO2 and CO combined with back-trajectories helped us
to distinguish between fossil fuel emissions and other CO2 sources. The
ΔCO/ΔCO2 ratios (R2 = 0.33 to 0.88, slopes = 2.42 to
10.37), calculated for anthropogenic-influenced air masses over different
countries/regions matched national inventories quite well, showing that
airborne measurements can help to identify the origin of fossil fuel
emissions in the PBL even when distanced by several days/hundreds of kms
from their sources. We have compared airborne CO2 observations to
nearby ground station measurements and thereby, confirmed that measurements
taken in the lower few meters of the PBL (low-level ground stations) are
representative of the local scale, while those located in the free
troposphere (FT) (moutain stations) are representative of atmospheric
CO2 regionally on a scale of a few hundred kilometers. Stations located
several 100 km away from each other differ from a few ppm in their
measurements indicating the existence of a gradient within the free
troposphere. Observations at stations located on top of small mountains may
match the airborne data if the sampled air comes from the FT rather than
coming up from the valley. Finally, the analysis of the CO2 vertical
variability conducted on the 14 profiles recorded in each campaign shows a
variability at least 5 to 8 times higher in the PBL (the 1-σ
standard deviation associated to the CO2 mean of all profiles within
the PBL is 4.0 ppm and 5.7 ppm for CAATER-1 and CAATER-2, respectively) than
in the FT (within the FT, 1-σ is 0.5 ppm and 1.1 ppm for CAATER-1
and CAATER-2, respectively). The CO2 jump between the PBL and the FT
equals 3.7 ppm for the first campaign and −0.3 ppm for the second campaign.
A very striking zonal CO2 gradient of about 11 ppm was observed in the
mid-PBL during CAATER-2, with higher concentrations in the west than
in the east. This gradient may originate from differences in atmospheric
mixing, ground emission rates or Autumn's earlier start in the west. More
airborne campaigns are currently under analysis in the framework of the
CARBOEUROPE-IP project to better assess the likelihood of these different
hypotheses. In a companion paper (Xueref-Remy et al., 2011, Part 2), a
comparison of vertical profiles from observations and several modeling
frameworks was conducted for both campaigns. |
| |
|
| Teil von |
|
|
|
|
|
|
|
|