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www.geosci-model-dev-discuss.net/2/639/2009/
doi:10.5194/gmdd-2-639-2009
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Simplified aerosol modeling for variational data assimilation
1Laboratoire des Sciences du Climat et de l'Environnement, L'Orme de Merisier, Gif sur Yvette, France
2Met Office, Hadley Centre, Exeter, UK
Abstract. We have developed a simplified aerosol model together with its tangent linear and adjoint versions for variational assimilation of aerosol optical depth with the aim to optimize aerosol emissions over the globe. The model was derived from the general circulation model LMDz; it groups together the 24 aerosol species simulated in LMDz into 4 species, namely gaseous precursors, fine mode aerosols, coarse mode desert dust and coarse mode sea salt. The emissions have been kept as in the original model. Modifications, however, were introduced in the computation of aerosol optical depth and in the processes of sedimentation, dry and wet deposition and sulfur chemistry to ensure consistency with the new set of species and their composition.
The simplified model successfully manages to reproduce the main features of the aerosol distribution in LMDz. Differences between the original and simplified models are mainly associated to the new deposition and sedimentation velocities consistent with the definition of species in the simplified model and the simplification of the sulfur chemistry. Furthermore, simulated aerosol optical depth remains within the variability of AERONET observations for all aerosol types and all sites throughout most of the year.
Sensitivity analyses with the tangent linear version show that the simplified sulfur chemistry is the dominant process responsible for the strong non-linearity of the model.
Discussion Paper (PDF, 3813 KB) Interactive Discussion (Closed, 4 Comments) Final Revised Paper (GMD)
Citation: Huneeus, N., Boucher, O., and Chevallier, F.: Simplified aerosol modeling for variational data assimilation, Geosci. Model Dev. Discuss., 2, 639-680, doi:10.5194/gmdd-2-639-2009, 2009. Bibtex EndNote Reference Manager XML
