ORCHIDAS DESCRIPTION

The ORCHIDAS software utility has been developed to optimize the ORCHIDEE model parameters using various observational data.
The current version is adapted to work with the following data:

• in-situ eddy-covariance flux measurements (FLUXNET),
• satellite measurements of vegetation activity (MODIS NDVI),
• atmospheric CO₂ concentration measurements.

It can be easily adapted to work with other data types through xml configuration files without changing the core code.

The optimization can be done using several approaches:

• variational approach (L-BFGS-B algorithm),
• Monte-Carlo approach (Genetic Algorithm or Particle Filter Algorithm),
• iterative approach (direct iterative solution).

Besides, some additional functions are implemeneted in ORCHIDAS:

• sensitivity analysis (Morris method),
• epsilon test (estimate of the optimal perturbation of ORCHIDEE parameters used in the gradient calculation),
• spin-up (ORCHIDEE carbon pools saturation to equilibrium).

The code is written in python by V. Bastrikov on the basis of different modules developed in different languages and different years by C. Bacour, N. Raoult, N. MacBean, S. Leonard, P. Peylin, D. Santaren.