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Title:
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Inverse modelling of European N2O emissions: assimilating observations from different networks
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Author(s):
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Corazza, M.; Bergamaschi, P.; Vermeulen, A.T.; Aalto, T.; Haszpra, L.; Meinhardt, F.; O’Doherty, S.; Thompson, R.; Moncrieff, J.; Popa, M.E.; Steinbacher, M.; Jordan, A.; Dlugokencky, E.; Bruhl, C.; Krol, M.C.; Dentener, F.
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Published by:
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Publication date:
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ECN
Biomass, Coal and Environmental Research
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17-3-2011
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ECN report number:
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Document type:
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ECN-W--11-013
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Article (scientific)
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Number of pages:
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19
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Published in: Atmospheric Chemistry and Physics (European Geosciences Union), , 2011, Vol.11, p.2381 -2398.
Abstract:
We describe the setup and first results of an inverse modelling system for atmospheric N2O, based on a four-dimensional variational (4DVAR) technique and the atmospheric transport zoom model TM5. We focus in this study on the European domain, utilizing a comprehensive set of quasi-continuous measurements over Europe, complemented by N2O measurements from the Earth System Research Laboratory of the National Oceanic and Atmospheric Administration (NOAA/ESRL) cooperative global air sampling network. Despite ongoing measurement comparisons among networks parallel measurements at a limited number of stations show that significant offsets exist among the different laboratories. Since the spatial gradients of N2O mixing ratios are of the same order of magnitude as these biases, the direct use of these biased datasets would lead to significant errors in the derived emissions. Therefore, in order to also use measurements with unknown offsets, a new bias correction scheme has been implemented within the TM5-4DVAR inverse modelling system, thus allowing the simultaneous assimilation of observations from different networks. The N2O bias corrections determined in the TM5-4DVAR system agree within ~0.1 ppb (dry-air mole fraction) with the bias derived from the measurements at monitoring stations where parallel NOAA discrete air samples are available. The N2O emissions derived for the northwest European and east European countries for 2006 show good agreement with the bottom-up emission inventories reported to the United Nations Framework Convention on Climate Change (UNFCCC). Moreover, the inverse model can significantly narrow the uncertainty range reported in N2O emission inventories for these countries, while the lack of measurements does not allow to reduce the uncertainties of emission estimates in southern Europe.
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