Version 2 (modified by peylin, 10 years ago) (diff)



20/09/2012 Developers meeting

Present: the meeting was held in Jussieu (~10 persons) with video links to the LSCE (~8 persons), Barcelona-Spain (Jan Polcher), Roma-Italy (Frederique), UA-Belgium (2 persons) and UG-Belgium (2 persons)

1. News

  • The latest trunk includes the documentation and the 11-layer hydrology scheme
  • The Lib IGCM meeting will be held on Octber 9th (Jussieu) and 10th (LSCE).
  • The structure of the new website is available, more work is needed on its content

2. The presentation

Camille Risi presented the inclusion of isotopes and tracers in the hydrological fluxes in ORCHIDEE.(see Presentation_isotopes)

3. Questions and Discussion

  • Although fractionation occurs for all phase changes, the current isotope implementation does not fully account for fractionation during freezing, thawing, snowing and smelting. The current models has some simple assumptions adressing this issue.
  • Individual molecules can be tagged and their path can be tracked. Tagging is available for geographical regions (e.g. the different oceans) or processes (e.g. transpiration).
  • It is hoped that the 11-layer hydrology could resolve the long standing issue of vertical distribution of isotopes in soil profiles.
  • For the moment, the istope scheme neglect molecular diffusion, including this process is not high on the priority list.
  • Isotopic fractionation could be applied on the AR5 simulations to predict continental recycling under future climate.
  • Isotopic fractionation hasn't been used for parameter optimisation yet but it seems feasible and worth trying.


05/07/2012 Developers meeting

Present: Camille Risi, Chao Yue, Matthieu Guimberteau, Kim Naudts, Aude valade, Sebastiaan Luyssaert, Juliette Lathiere, Anne Cozic, Josephine Ghattas, Niclas Vuichard, Didier Solyga, James Ryder, Jan Polcher (video), Patricia Cadule.

1. News

  • The latest trunk now includes diagnostic VOC emissions, this development is not tagged yet.
  • The documentation is now being merged to the hydrology branch which in turn is merged to the trunk. However, before this merge can be released, the water fluxes simulated the old hydrology scheme 'choinel' in the merge need to be identical to those simulated with the last tag (1.9.6). Following this release the new hydrology scheme will require some further testing, especially its interaction with stomate through plant water stress. A post-doc will be hired on the EMBRACE project to improve the soil-plant-atmosphere coupling of this merge.
  • Developers meetings will start again in September (date to be communicated).
  • In September a LibIGCM users meeting will be organised to discuss the current possibilities of this library of scripts that make up the run environment of ORCHIDEE (and the other components of the IPSL-ESM).

2. The presentation

The semi-analytic spin-up by Didier Solyga and Nicolas Vuichard (see Presentation_spinup)

3. Questions and discussion

  • The current approach relies on the matrix that describes the transfer coefficients between pools and their temperature/moisture sensitivity. Hence the approach should not limit the introduction of new carbon pools such as discretizing the active, slow and passive pools with soil depth. Similar, litter pools i.e. coarse woody debris could be added (as required for forest management).
  • The semi-analytic approach is integrated in the code and it is not straightforward to make the code more generic. This implies that the branch will have to move towards the trunk if they want to make use of this approach. The issue of branch divergence was discussed but did not result in an action.
  • The methods relies on the input to the litter pools to reach equilibrium soil C-pools. Fire, harvest, DOC or other lateral C-fluxes are accounted for in the soil C-pools. As a diagnostic NBP (net biome production) is stored in the restart files. NBP is not required to restart the model, nevertheless, it is stored in the restart to give the user a diagnostic variable to test the initial state of the simulation when the semi-analytic spin-up is used. NBP can be considered as some documentation of the spin-up.
  • The semi-analytic spin-up uses an objective criteria (epsilon) to stop the spin-up. Hence the spin-up does no longer depend on the user and a set of commonly used spin-ups could be stored and shared among users to save computation time.
  • Once the semi-analytic solution is merged in the trunk, forcesoil can be dumped and will no longer be maintained. The number of iterations required by the semi-analytic spin-up depends on the biomass. Hence, there is still room to use testomate. Given the possible instabilities of testomate, full ORCHIDEE could be used as an alternative. This will be further investigated.

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