Simulation of atmospheric CO2 over Europe and western Siberia using the regional scale model REMO

Anne Chevillard (1) , Ute Karstens (2) , Philippe Ciais (1, 3) , Sébastien Lafont (4) , Martin Heimann (2)

1 LSCE - Laboratoire des Sciences du Climat et de l'Environnement [Gif-sur-Yvette]
2 MPI-BGC - Max-Planck-Institut für Biogeochemie
3 ICOS-ATC - ICOS-ATC
4 CESBIO - Centre d'études spatiales de la biosphère

The spatial distribution and the temporal variability of atmospheric CO 2 over Europe and western Siberia are investigated using the regional atmospheric model, REMO. The model, of typical horizontal resolution 50 km, is part of a nested modelling framework that has been established as a concerted action during the EUROSIBERIAN CARBONFLUX project. In REMO, the transport of CO 2 is simulated together with climate variables, which offers the possibility of calculating at each time step the land atmosphere CO 2 fluxes as driven by the modelled meteorology. The uptake of CO 2 by photosynthesis is calculated using a light use efficiency formulation, where the absorbed photosynthetically active solar radiation is inferred from satellite measurements. The release of CO 2 from plant and soil respiration is driven by the simulated climate and assumed to be in equilibrium with photosynthesis over the course of one year. Fossil CO 2 emissions and air-sea fluxes within the model domain are prescribed, whereas the influence of sources outside the model domain is computed from as a boundary condition CO 2 fields determined a global transport model. The modelling results are compared against pointwise eddy covariance fluxes, and against atmospheric CO 2 records. We show that a necessary condition to simulate realistically the variability of atmospheric CO 2 over continental Europe is to account for the diurnal cycle of biospheric exchange. Overall, for the study period of July 1998, REMO realistically simulates the short-term variability of fluxes and of atmospheric mixing ratios. However, the mean CO 2 gradients from western Europe to western Siberia are not correctly reproduced. This latter deficiency points out the key role of boundary conditions in a limited-area model, as well as the need for using more realistic geographic mean patterns of biospheric carbon fluxes.

Domaines: Océan, Atmosphère; Interfaces continentales, environnement

Anne Chevillard, Ute Karstens, Philippe Ciais, Sébastien Lafont, Martin Heimann. Simulation of atmospheric CO2 over Europe and western Siberia using the regional scale model REMO. Tellus B - Chemical and Physical Meteorology, 2002, 54 (5), pp.872-894. ⟨10.1034/j.1600-0889.2002.01340.x⟩. ⟨hal-02923935⟩