Impact of improved land surface model physics on simulated climate variability and change

Résumé

The land is a pivotal component of the Earth and its climate system since many processes of natural variations in the climate system, which affect the environment and human society, are governed by the land surface. Hence, a good representation of the thermal and hydrological states of the land surface in climate models is important to have a realistic simulation of the coupling between the atmosphere and the lito-biosphere. An influencing factor for improving the realism of the ground energy and water balance in climate models is the depth of the land zero-flux Bottom Boundary Condition Placement (BBCP). Despite recent improvements in modeling land surface processes in climate models, only limited attention has been directed toward the effect of the BBCP in Land Surface Models (LSMs) and its impact on the representation of terrestrial thermodynamics. Previous analytical and modeling studies suggest that the simulation of subsurface thermodynamics in current-generation climate models is not accurate due to the zero-heat-flux BBCP being imposed too close to the surface. An insufficiently deep land component in current-generation climate models compromises the simulation of the terrestrial thermal state and can influence land-atmosphere interactions. Further improvements in LSMs relate to the representation and sensitivity of coupling processes between the ground thermodynamic and hydrological regimes. As moisture is one of the main drivers of near-surface climate interactions, the hydro-thermodynamic coupling is crucial for studying the impacts of perturbations caused by human activity. Under climate change conditions, some areas and ecosystems are more vulnerable to a rapidly warming world than others...