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Titel:
Influence of interannual variability of transport on surface based measurements of greenhouse gases
 
Auteur(s):
Cabello Ganuza, M.; Vermeulen, A.T.; Orza, J.A.G.
 
Gepubliceerd door: Publicatie datum:
ECN Biomassa, Kolen en Milieuonderzoek 24-10-2011
 
ECN publicatienummer: Publicatie type:
ECN-M--11-096 Conferentiebijdrage
 
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Samenvatting:
On the annual to climatic time scales global processes will dominate the variations in observed concentrations of greenhouse gases. Disentangling the different processes at different timescales requires the use of atmospheric transport models that are sufficiently adequate at the required scales in time and space. In this paper we will use trajectory cluster analysis to derive an estimate for the contribution of transport to the variations in greenhouse gas concentrations, as observed at Cabauw tall tower (4.927 E, 51.971 N, -0.7 m a.s.l.) in the period 1992-2011 (vermeulen et al, 2011). The anomalies in the methane concentration growth rate in this period can at least partly be explained by the changes in global circulation connected to the North Atlantic Oscillation (NAO). The influence of NAO extends to transport directions, mean wind speeds and atmospheric stabilities. The influence of the use of different meteorological input datasets for the trajectory calculations is also investigated and evaluated using the match between measured and predicted forward concentrations of methane and carbon dioxide at Cabauw and Mace Head station. Winter and summer time high concentrations coincide with low NAO index values while the low concentration periods are often associated with high NAO indices. For carbon dioxide the pattern is less clear due to the fact that winter time concentrations in the northern hemisphere are mainly governed by emissions while summer soncentrations are also influenced by assimilation uptake.


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