Abstract. SURFEX is a new externalized land and ocean surface platform that describes the surface fluxes and the evolution of four types of surfaces: nature, town, inland water and ocean. It is mostly based on pre-existing, well-validated scientific models that are continuously improved. The motivation for the building of SURFEX is to use strictly identical scientific models in a high range of applications in order to mutualise the research and development efforts. SURFEX can be run in offline mode (0-D or 2-D runs) or in coupled mode (from mesoscale models to numerical weather prediction and climate models). An assimilation mode is included for numerical weather prediction and monitoring. In addition to momentum, heat and water fluxes, SURFEX is able to simulate fluxes of carbon dioxide, chemical species, continental aerosols, sea salt and snow particles. The main principles of the organisation of the surface are described first. Then, a survey is made of the scientific module (including the coupling strategy). Finally, the main applications of the code are summarised. The validation work undertaken shows that replacing the pre-existing surface models by SURFEX in these applications is usually associated with improved skill, as the numerous scientific developments contained in this community code are used to good advantage.

Two 30-year simulations corresponding to 1960–1989 and 2070–2099 have been performed with a variable resolution atmospheric model. The model has a maximum horizontal resolution of 0.5 over the Mediterranean Sea. Simulations are driven by IPCC-B2 scenario radiative forcing. Sea surface temperatures (SSTs) are prescribed from monthly observations for the present climate simulation, and from a blend of observations and coupled simulations for the scenario. Another pair of forced atmospheric simulations has been run under these forcings with the same uniform low resolution as the coupled model. Comparisons with observations show that the variable resolution model realistically reproduces the main climate characteristics of the Mediterranean region. At a global scale, changes in latitudinal temperature profiles are similar for the forced and coupled models, justifying the time-slice approach. The 2 m temperature and precipitation responses predict a warming and drying of the Mediterranean region. A comparison with the coupled simulation and forced lowresolution simulation shows that this pattern is robust. The decrease in mean precipitation is associated with a significant decrease in soil wetness, and could involve considerable impact on water resources around the Mediterranean basin

[1] The land surface model (LSM) ISBA-A-gs (Interactions between Soil, Biosphere and Atmosphere, CO 2 -reactive) is specifically designed to simulate leaf stomatal conductance and leaf area index (LAI) in response to climate, soil properties, and atmospheric carbon dioxide concentration. The model is run at the global scale, forced by the GSWP-2 meteorological data at a resolution of 1°for the period of 1986-1995. We test the model by comparing the simulated LAI values against three satellite-derived data sets (ISLSCP Initiative II data, MODIS data and ECOCLIMAP data) and find that the model reproduces the major patterns of spatial and temporal variability in global vegetation. As a result, the mean of the maximum annual LAI estimates of the model falls within the range of the various satellite data sets. Despite no explicit representation of phenology, the model captures the seasonal cycle in LAI well and shows realistic variations in start of the growing season as a function of latitude. The interannual variability is also well reported for numerous regions of the world, particularly where precipitation controls photosynthesis. The comparison also reveals that some processes need to be improved or introduced in the model, in particular the snow dynamics and the treatment of vegetation in cultivated areas, respectively. The overall comparisons demonstrate the potential of ISBA-A-gs model to simulate LAI in a realistic fashion at the global scale.