Modelling energy and CO2 fluxes with an interactive vegetation land surface model-Evaluation at high and middle latitudes

We developed ISBA-CC, a new version of the ISBA land surface model, to represent the fluxes and reservoirs of the terrestrial carbon cycle. The simulated latent heat flux, sensible heat flux and net ecosystem exchange are validated against in-situ measurements at 26 sites of the FLUXNET network, located at temperate and high latitudes of the Northern Hemisphere. Overall, ISBA-CC captures well the temporal variations of the fluxes, from the diurnal to the seasonal and the inter-annual scales. The best results are obtained for deciduous broadleaf and needle leaf forests, while the worst are found for agricultural sites, suggesting the need to take into account agricultural practices in order to better simulate both the energy fluxes and the net carbon flux. The ranking of the sites in terms of scores is consistent for the different fluxes. We show that taking into account the response of heterotrophic respiration to soil moisture allows a better representation of the variations of the net ecosystem exchange along with soil water content. ISBA-CC also compares favourably with other terrestrial ecosystem models. All these results show that the model matches the observed variability driven by the climate and can be used to assess the response of the terrestrial biosphere to future climate changes.