Improving the parameterization of vegetation cover variability in land surface models based on satellite observations

Vegetation is highly dynamic at seasonal, inter-annual, decadal and longer timescales. These dynamics are strongly coupled with hydrological, biogeochemical and bio-physical processes. In global land surface models,  this coupling is controlled by  parameterizations of the effective sub-grid vegetation cover that controls amongst others modelled evapotranspiration, albedo and surface roughness. In this study we aim to explore the use of observational satellite datasets of LAI and Fraction of green vegetation Cover (FCover) for an improved model parameterization of effective vegetation cover.
The effective vegetation cover can be described by exponential functions resembling the Lambert Beer law of extinction of light under a vegetated canopy  (1-e^-k*LAI), with k the canopy light extinction coefficient. In HTESSEL (i.e. the land surface model in EC-EARTH) k has been set to a constant value of 0.5 so far. However, k varies for different vegetation types as it represents the structure and the clumping of a vegetation canopy. For example tree canopies are more clumped than grasses, resulting in a larger effective coverage. In this study we optimize the canopy extinction coefficient k using the LAI and FCover satellite products for different vegetation types (ESA-CCI land cover), with FCover equivalent to the model effective vegetation cover.  
This effort results in a vegetation dependent relation between LAI and effective vegetation cover that is implemented in HTESSEL. The improved effective vegetation cover parameterization is evaluated using offline model simulations. To evaluate the sensitivity to the new parameterization, modelled evaporation, discharge and skin temperature are compared with station and satellite observations.