orchidee

ORCHIDEE is a dynamic global vegetation and land-surface model developed at the Laboratoire des sciences du climat et de l’environnement (LSCE) in France. It is a component of the SURFEX framework and is used to simulate exchanges of energy, water, and carbon between the land surface and the atmosphere in both offline and coupled climate simulations. The model represents the land surface on a global grid with multiple plant functional types (PFTs) that determine photosynthesis, respiration, phenology, and stomatal behavior.

Key processes in ORCHIDEE include photosynthesis based on established formulations, transpiration through stomatal conductance, and the transfer of carbon among litter, soil, and root pools. The model also represents soil moisture and hydrology, with regional variations in drainage and rooting depth. Some versions of ORCHIDEE include dynamic vegetation, allowing vegetation composition to respond to climate and CO2. A widely used variant, ORCHIDEE-CN, couples carbon and nitrogen cycles to simulate nutrient limitations on productivity.

Applications of ORCHIDEE span global and regional climate research. It is employed to study contemporary and historical carbon fluxes, land-atmosphere feedbacks, and projections under future climate scenarios. The model’s outputs are often evaluated against flux-tower networks and satellite observations and intercompared with other land-surface models to understand uncertainties in the terrestrial carbon and water cycles.

Impact and accessibility: ORCHIDEE has influenced numerous studies in global and regional climate research and is actively developed within the IPSL research community. Its variants, including nitrogen-coupled versions, extend its applicability to a broader set of biogeochemical processes.

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