wiki:GroupActivities/Meetings/Developer

Version 64 (modified by peylin, 9 months ago) (diff)

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HOW TO organize an ORCHIDEE-dev meeting

For each ORCHIDEE-dev meeting a main organizer is decided during a weekly meeting as well as the main theme of the meeting. The main organizer will then organize the meeting as much as possible outside the weekly meetings.

Check-list to follow for the main organizer:

  • Define subject and list of speakers.
  • Define date among the most concerned people.
  • Book a large-enough meeting room with video-conference. In Jussieu, the Atrium rooms can be booked online : http://www.cpm.upmc.fr/fr/visioconf/visioconferences.html; Email: demandes-visio-cpm@… or David.Martial@…
  • Reserve RENATER link https://renavisio.renater.fr/
  • Send a first mail to orchidee-dev preferentially 3 weeks before, plus reminders 1 week and 1 day before.
  • Include a detailed agenda with talks' titles, time slots, and locations().
  • Ask P. Peylin if he wants to do some project information.
  • Update the reports below with the talks pdfs + additional notes if justified.

Reports from previous ORCHIDEE developers meetings

07/01/2020 Routing scheme in ORCHIDEE

Specific meeting to present and discuss different options for the routing scheme in ORCHIDEE and the associated flood-plains

The different presentations are:

  • Intro with few news (Philippe P) ORC-DEV_Jan2020_Intro.pdf
  • New routing scheme based on Hydrological Transfert Units (HTU) for high resolution simulations (Jan) DEV-Meeting_presentation_routing_Jan.pdf; the new scheme allows to decompose the water demand between ecological flow for the river, agriculture demand (irrigation), Domestic water use and hydro-electricity. It also accounts for dams to sustain the different demands. Key remaining issues are link to parallelisation.
  • Ground water development and links with the routing scheme (Agnes) ORCHIDEE_DEV_routing_070120_Agnes.pdf; i) Agnes tested a new approach for the time constant of the water in the Ground Water reservoir (from Boussinesq equation) but it degrades the river flows; ii) They have inserted a subgrid tiling with lowland and highland units that exchange water (from highland to lowland); this has an impact on the soil moisture and ET of the grid.
  • Flood plain innundation in the ORCHILEAK version (Rony Lauerwald) Lauerwald_20200107.pdf; Rony implemented and tested a new approach for the floodplain based on a threshold (Bankfull) over which the river start to fill the potential floodplain; It largely improves the dynamic of flooded area over the Amazone. Such scheme will be transfered into the TRUNK together with Agnes.
  • Toward a new high resolution floodplain scheme (Anthony Schrapffer) ORCHIDEE_Anthony_high-resolution-floodplains.pdf Anthony is implementing a potential new floodplain scheme working on the "Paraguay river and flooding region" in South America; It is based on the propagation of a flooding waves depending on topography.

21/02/2019 Phosphorus cycle in ORCHIDEE

Daniel Goll presented the ORCHIDEE version CNP which includes the impact of the Phosphorus cycle on the overall model behavior (mainly the productivity) Goll_Phosphorus_LSCE_Meeting.pdf

The presenation discussed in turn:

  • Why a phosphorus cycle in ORCHIDEE
  • Which processes are implemented
  • How does the CNP version works
  • Which application can be targeted with the CNP version
  • Technical aspects

At the end of the meeting, the technical discussion revealed that substantial work is needed to integrate it in the TRUNK (that will include CAN-CN); D.G. is willing to strongly help to achieve this merge.

15/03/2018 and 16/03/2018 Coordination between plant hydraulics and photosynthesis

The meeting consisted of three parts spread over two days: (1) A presentation of the interplay between xylem, phloem, sugar sinks and photosynthesis by Teemu Hölttä slides. The models discussed by Teemu have been published in Niikinmaa et al 2013 and Hölttä et al 2016. (2) Angi Mauranen introduced the general framework as well as a series of analytical solutions to calculate stomatal conductance while accounting for the hydraulic architecture of tall vegetation (Dewar et al 2017) slides. During the subsequent discussion Sebastiaan Luyssaert presented the expectations the ORCHIDEE-team has in terms of its photosynthesis model slides and Thomas Janssen presented the results of a literature study on stomatal functioning in the Amazon slides. (3) During the final session the group discussed how to proceed working on this topic without formal funding for this work.

Participated in the discussions: Marc Peaucelle (remotely), Kim Naudts (remotely), Aude Valade (remotely), Emilie Joetzer (remotely), Timo Vessala, Yann Saumon, Angi Mauranen, Teemu Hölttä, Nicolas Viovy, Daniel Goll, Fabienne Maignan, Philippe Peylin, Thomas Janssens, Sebastiaan Luyssaert (minutes)

Conclusions: The attention for plant hydraulic architecture in Earth system modelling is increasing. Photosynthesis models has been high on the agenda for a long time resulting in a steady flow of new model developments. Coordination of light and CO2 limitation in photosynthesis has received quite some attention recently and bears the promise to simulate, rather than prescribe, several of the key parameters of the current photosynthesis models. Given the physiological coupling between photosynthesis and transpiration, models accounting for the coordination between photosynthesis and within-plant water transport are a logic advancement.

At present the dynamic model by Niikinmaa et al 2013 is among the most complete representations of the coupling between plant hydraulics, photosynthesis and plant growth. The model is computationally very demanding. Assuming steady state, a simplified version of the model was published by Hölttä et al 2106. This version accounts for xylem, phloem, sugar sinks and photosynthesis but no longer accounts for cavitation and water storage. The analytical solutions further reduce the number of processes that are accounted for but would overcome the need to recalculate gs in case there is plant water stress. The analytical solution retained the physical basis of the parameters as in the steady-state model but basically accounts for the upward water flow through plant hydraulic architecture. Accounting for hydraulic architecture of vegetation requires that the different vegetation components have dimensions (height, diameter, ...) as is the case in ORCHIDEE-CN-CAN. As such it was thought that in terms of functionality the analytical solution would add little to the functionality currently present in ORCHIDEE-CN-CAN. On the other hand, adding the analytical solution would require a lot of changes to the current trunk.

Long-term goal: coupling a unified photosynthesis model accounting for coordination/co-limitation with a closed within-plant water cycle with the aim to better account for the short term responses of photosynthesis to drought, the long-term changes in water use efficiency, as well as the source-sink dynamics which are currently poorly represented in most land surface models. A balanced representation of these processes would require a dynamic approach towards simulating the root profile as well as an investment on how to make best use of the interplay between soil water in the 11-layer hydrology and the root profile.

Draft roadmap to achieve this long-term goal:

  • Marc keeps working on the coordination, it would be good to study how easily this new approach could be added to either ORCHIDEE, ORCHIDEE-CN, ORCHIDEE-MICT or ORCHIDEE-CN-CAN.
  • Aude’s Marie Curie fellowship partly overlaps with the long-term objectives (i.e., adding water storage, adding dynamic roots, testing the analytical solution)
  • Thomas PhD’s study could be steered towards overlapping with the long-term objectives (i.e., rather than moving parts of ORCHIDEE into his Python code of Teemu’s steady state model, the missing parts of Teemu’s model could be integrated in ORCHIDEE)
  • Fabienne is interested in photosynthesis and showed interest in contributing to this work
  • If some progress is made in the coming 10 months, we should apply for funding dedicated to supporting Finnish-French collaboration through exchange visits and workshops.
  • Kim offered Angi some help with the nuts and bolts of JSBACH
  • Sebastiaan would like to prepare a scheme showing whether and how the different components of the steady-state model are currently formalized in ORCHIDEE-CN-CAN.
  • A shared folder containing the presentations and key papers was established access can be requested through Sebastiaan.

06/03/2018 - Regional coupled simulations

Meeting at LSCE with videoconference, about 25 attendees

For more information on the regional modeling activities at IPSL (meeting every Thursday) contact Jan Polcher.

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30/01/2018 - Evaluation of recent ORCHIDEE simulations

Meeting in Jussieu with videoconference, about 25 attendees

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05/12/2017 - Description of the CMIP6 version of ORCHIDEE

Meeting at LSCE with visioconference; description of the main update for CMIP6 (vs CMIP5), about 30 attendees

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06/10/2015 - Bare soil evaporation (BSE) and roughness length (z0)

The meeting was held in Jussieu with video links to LSCE and Sebastiaan, about 20 persons attended

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31/03/2015 - XIOS in ORCHIDEE

Present: the meeting was held in Jussieu with video links to LSCE and LGGE, about 25-30 persons attended the meeting

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27/01/2015 - THE NEW PHOTOSYNTHESIS SCHEME

Present: the meeting was held in Jussieu with video links to LSCE; about 30 persons attended the meeting

First brief presentation of the PROJECT news by Philippe Peylin (see Project_News.pdf)

Main Photosynthesis Presentation by Nicolas Vuichard (see Photosynthesis.pdf)


We then discussed and raised few points:

  • What is the impact of the Photosynthesis changes on the transpiration flux : Nicolas may try to answer that in order to complete his presentation that could then serve as a "ref document"
  • with the new scheme, the Vcmax values that are given correspond now to values at 25C and not at the optimal (so they can be slightly higher depending on the temperature)
  • The impact of leaf age is not directly illustrated in the presentation but it does play also a role for the values of Vcmax

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17/06/2014 - THE SOIL THERMAL DYNAMIC IN ORCHIDEE

Present: the meeting was held in Jussieu with video links to LSCE; about 30 persons attended the meeting

Presentation by Fuxing Wang

The presentation: (see Fuxing.pdf)


We then discussed how to interface the new scheme with the new multi-layers snow albedo, the problem of permafrost that would require a soil depth more on the order of 100 m than 8 m, and how this work could benefit to CMIP6

Note that for the coupling with LMDz, there is a page on the wiki to "brainstorm" on the major issues that we need to solve (linked to energy conservation and the need to have constant net radiative forcing in ORC during two call of the radiative transfert in LMDz) link

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17/06/2014 - CARBON AND HYDROLOGY MODELING IN THE AMAZON

Present: the meeting was held in Jussieu with video links to LSCE; about 30 persons attended the meeting

  • Introduction (see 00_Introduction.pdf)
  • Hans VERBEECK: Comparisons of ORCHIDEE with the other AMAZALERT models, for carbon flux and stocks at the basin scale + Carbon stocks and fluxes, validation with biomass and litterfall data. Sensitivity of carbon related parameters. (Marjolein DE WEIRDT) (see 01_Verbeeck.pdf)
  • Nicolas NAJDOVSKI: Work in context of FOREST project (see 03_Najdovski.pdf)
  • Jonathan BARICHIVICH: Preparing ORCHIDEE-DOFOCO for data assimilation in the Amazon within GEOCARBON (see 02_Barichivich.pdf)
  • Natasha MCBEAN: PFT2 optimisation of Sylvain Kuppel (see 04_McBean.pdf)
  • Nicolas DELBART & Maëlle ROSENTHAL: Relationship between soil types/topography with NPP, mortality, and with model errors in Amazonia (see 05_Delbart_Rosenthal.pptx)
  • Philippe CIAIS: Limitations of phosphorus of NPP and carbon storage (see 06_Ciais.pdf)
  • Juan-Pablo BOISIER: Trends in the Amazon hydrology simulated between 1980 and 2050 in response to a severe scenario of deforestation (see 07_Boisier.pdf)
  • Matthieu GUIMBERTEAU: The hydrological modeling with ORCHIDEE in the Amazon basin (see 08_Guimberteau.pdf)

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25/03/2014 - DATA ASSIMILATION WITH ORC AND PARAMETER OPTIMIZATION

Present: the meeting was held in Jussieu with video links to LSCE; about 30 persons attended the meeting

  • Philippe Peylin / Fabienne Maignan: Presentation of the futur merges with the different ORC branches and the results of the logo contest (see Orchidee_merge_03-2014.pdf).
  • Natasha Macbean (LSCE): Presentation of Data Assimilation concept and applications with ORCHIDEE; A first presentation illustrates the concepts (see DA_tutorial.pdf); A second presentation provides important exemples with ORCHIDEE (see NM_DA_OrchDev.pdf)
  • Catherine Ottle (LSCE): Presentation of the main results of the PhD of Simon Benavides around the optimization of SECHIBA with surface temperature, using YAO software (see assim_YAO_ORCHIDEE.pdf)
  • Philippe Peylin (LSCE): Presentation of additional exemple of DA with ORCHIDEE and of the tools that are under constructions (see Orchidee_DA_peylin_2014.pdf)

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03/12/2013 - FIRES

Present: the meeting was held in Saclay with video links to Jussieu about 30 persons attended the meeting

1. The presentations

  • Ann COZIC (LSCE) introduced the parallelisation of LMDzORC with OPENMP (previously MPI) (see Presentation_OMP).
  • Chao YUE (LSCE) presented 'Spitfire in ORCHIDEE'. The presentation focussed on simulating the burned area and simulating the emission through fire. (see Presentation_feux_LSCE)
  • Solène TURQUETY (LMD) (see Presentation_LMD)

2. Questions and Discussion

  • The code has 4 different parallelisations build in (OPENMP, MPI(default), hybrid and sequential). Make sure to compile LMD and ORCHIDEE with the same parallelisation.
  • Before running some modifications will be required to some *.cards.
  • It is worth the effort because it can save a substantial amount of run time and the results are conserved.
  • How does the model handle human ignition of fires and which drivers should be used?
  • Are the parameters scale independent. This should be tested before running at different spatial resolutions
  • Currently, fire duration does not depend on the available biomass and hence the presence/absence of an understorey is not taken into account.
  • Changes in litter decomposition should be made dependent on the amount of charcoal in the litter
  • In the current version PFTs recover very fast from a fire this is because there is no N in the model but even more importantly because the LAI and thus the GPP and NPP recover immediately the year after a fire. Better growth representation would be very useful.
  • Uncertainty in the emissions are equally caused by uncertainties in its components
  • injection heights are being modelled off-line by LMD (mean height seems OK but large variation from one fire to another).

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24/10/2013 - PRESENTATION OF THE DOFOCO BRANCH

Present: the meeting was held in Jussieu with video links to LSCE, UG-Belgium.

The main objective of the meeting was to present the DOFOCO branch developped by Sebastiaan Luyssaert group to the rest of the ORCHIDEE Developers/users.

Matthew Macgrath presented all developments made in the DOFOCO branch, especially the improvement on radiative transfert, multi-energy budget, forest management, carbon allocation. (see Presentation_dofoco)

Prior to the DOFOCO presentation, Josefine explained the use of LIBIGCM to make specific time series (see Presentation_libigcm)

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08/01/2013 and 29/01/2013 - GENERAL PRESENTATION FROM ALL USERS

Present: the meeting was held in Jussieu with video links to LSCE, UG-Belgium, and Grenoble. In total around 40 persons attended the meeting.

The objective of the meeting was that each users/developers of ORCHIDEE present himself and the subject of his research/developments (past and for the next year). Given the large number of persons, it was required to have only 2 transparency per participant and we also group the presentations by THEMES with an overview by a permanent at the begining. The themes are detailed below with link to the presentations.

The meeting went over 2 sessions 8 Jan and 29 Jan. As a remark, the presentations were informative and usefull to get an overview of the different ongoing developments and use of ORCHIDEE. However, it was suggested that next year we should focuss the meeting (on a specific theme) with more in depth presentations and try to cover all subject across a year.

1. Water cycle, river flows and water quality and the interaction with the biosphere under future climate

  • Background: studies quantifying the water cycle and its changes in chemical composition

Introduction: Agnes Ducharne for the water cycle and then Catherine Ottle

  • Contributions: Matthieu Guimberteau, Aurélien Campoy, Jan Polcher, Marta Camino Serrano, Anais Barella-Ortiz, Gerhard Krinner, Tao Wang, Isabelle Goutevin, Chloe Largeron, Claire Brutel, Sushi Peng, James Ryder

(see Presentation_water-cycle)

(see Presentation_energy+high-lat)

2. Coupled climate simulations, chemistry and new tracers

  • Background: Scientific questions related to the improvement of the coupled Atmosphere-Vegetation simulations (past, present, future), the inclusion of the chemistry and new tracers such as the isotopes.
  • Introduction: Frederic Cheruy
  • Contributions: Marc Stefanon, Juliette Lathiere (INCA), Thomas Verbecke, Camille Risi, Fracesca Guglielmo

(see Presentation_C.Risi) (see Presentation_F.Cheruy) (see Presentation_M.Stefanon) (see Presentation_F.Guglielmo) (see Presentation_J.Lathiere) (see Presentation_T.Verbecke)

3. Model Evaluation and parameter optimization

  • Background: Testing and improving the quality of the current versions of ORCHIDEE (coupled or off-line) and its subcomponents through Evalutiona/Validation? (proxies, isotopes, direct observations) and/or parameter optimization.
  • Introduction: Nicolas Vuichard (Evaluation) & Philippe Peylin (Optimization).
  • Contributions: Fabienne Maignan, Josefine Ghattas Sylvain Kuppel, Marc Peaucelle, Natasha Macbean, Marjolein De Weerdt, Hans Verbeek, Kun Tan, Thomas launois, Pascal Maugis

(see Presentation_Josefine)

(see Presentation_Evaluation-Optimization)

4. Climate and GHG attribution including fires.

  • Background: studies quantifying the contribution of individual biogeochemical and biophysical processes in the observed and or predicted environmental changes
  • Introduction: Nicolas Viovy and Patricia Cadule
  • Contributions: Didier Solyga, Bertrand Guenet, Chao Yue, Makoto Saito, Stijn Hantson, Ben Poulter, Tomomichi Kato, Gwenaelle Berthier

(see Presentation_Didier)

(see Presentation_GHG-Attribution)

5. Climate and land management

  • Background: studies using ORCHIDEE (coupled or off-line) to understand the effect of land cover and land management on biogeochemical cycles, biophysical processes and climate.
  • Introduction: Sebastiaan Luyssaert
  • Contributions: Juliane Otto, Kim Naudts, Matt Mcgrath, Yan Yuan, Toon de Groot, Amelie Rajeaud, Aude Valade, Abdul Traore, Jinfeng X, Yann Zhao

(see Presentation_Management)

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13/11/2012 - Grasslands and svn

Present: the meeting was held in Saclay with video links to Jussieu, UA-Belgium and UG-Belgium. In total 28 persons attended the meeting.

1. The presentations Jinfeng CHANG presented 'managed grasslands in ORCHIDEE with the inclusion of the specific module from PASIM grassland model' Josephine GHATTAS introduced the svn systems and its basic use (including commands)

2. Questions and Discussion

  • The link between the Grassland Module (GM) and stomate is established through the aboveground biomass
  • Although LAI seems to be extremely low at the end of the growing season, this is no effect on GPP because GPP is already limited by radiation at that time of the year
  • A Module to calculate the lateral fluxes is being worked on
  • Agnes' groups once made a map conatining the anthropogenic PFT's. this map is still available and is adjusted to be used with ORCHIDEE.

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20/09/2012 - Isotopes and tracers

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.

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05/07/2012 - Semi-analytic spin-up

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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10/05/2012 - 11-layer hydrology

Place: LSCE PRESENT: around 20 people from ORCHIDEE-DEV mailing list

The objective of the meeting was to present and discuss the results of the "ORCHIDEE - Hydrology 11 layers branch". This branch was created from the "AR5" main version, including all past developments on the new hydrology, including river routing, flood plains and some modifications due to soil freezing (LGGE work). The major contributions to the meeting were: (All presentations are accessible below)

1) Presentation of the 11 layer hydrology

Although prepared by Agnes (not present), the presentation was given by Matthieu G., with the exposition of the concept of this new hydrology scheme. A little discussion/precision was made on the changes compared to the initial scheme developped by Patricia De-Rosnay. It concern mainly the number of water budget per grid point. Initially a water budget was made depending on the soil characteristics (3 budget for three major types of soil) while now there is 3 budget for the three main vegetation classes (trees, grasses, crop).

Overall presentation prepared by Agnès Ducharne. See her Presentation.

2) Results from Matthieu for the Amazon basin

Matthieu compared several configurations (with/without STOMATE, different forcing files, and new hydro scheme versus old choisnel scheme) for the the Amazon basin. He looked at the river flow of the amazon and concluded that the current version with the new hydrology was leading to similar results than those obtained during previous work (with a different ORC version). Evaluation of the Hydro-Merge version over the Amazon River Basin by Matthieu Guimberteau. See his Presentation.

3) Result on the SIRTA (Aurelien)

(transparencies at the end of the general presentation of the new hydrology)

Aurelien Campoy presented few slides on a comparison made at the SIRTA site (Saclay Plateau) on a force mode (SAFRAN), without STOMATE. He compared for bare soil the evaporation from the "branch" version with that from an older version with the new hydrology (IGPBAC) and concluded on no significant differences

4) Results on the Mediterranean basin (Jan Polcher)

Jan compared simulations with new hydro between "the merge BRANCH" and his old working version, with WATCH forcing (without STOMATE). He obtained for July increased evapotranspiration with the merge branch, which seems to lead to a better agreement for the river discharge of major basins (Rhone).

Evaluation of the Hydro-Merge version over the Mediterranean Basin by Jan Polcher. See his Presentation.

4) Results at Fluxnet sites (Nicolas Vuichard)

Nicolas presentation a first comparison at several fluxnet site of the evapotranspiration between the new scheme and the old one WITH STOMATE. It turns out that the new hydrology leads to large day to day variations in the evapotranspiration that are probably unrealistics. This points to the strong need of "recalibrating the water stress functions with the new scheme and STOMATE"

Evaluation of the Hydro-Merge version on some Fluxnet sites by Nicolas Vuichard. See his Presentation.

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15/03/2012 - Radiative transfer through canopies

Place: Jussieu PRESENT: around 20 people from ORCHIDEE-DEV mailing list

  • Presentation by Juliane Otto of a "New Radiative Transfert scheme for ORCHIDEE" to compute the Albedo. See her Presentation. An active discussion followed the presentation of Juliane and in particular several points were mentionned:
    • Need to change the current handling of bare soil : "gather all PFT fractions not covered by leaves into PFT1 (bare soil)" with a new treatment : "consider separately the fraction covered or not by leaves for each PFT independantly". The Radiative transfert scheme will directly benefit from this improvement.
    • The proposed RT scheme uses Monte Carlo simulations to compute the path of the photon within the canopy: This need to be change to reduce the computing time and to have "reproductive" results.
    • The proposed RT scheme uses the output of "Forestry Management Module" to compute the geometry of the stand from from the tree diameters classes, height,... This need to be generalized so that the RT scheme works also with ORCHIDEE standard (without FM). Juliane plans to use some "standard geometry" following some work by B. Pinty.
    • The proposed RT scheme uses three main parameters for the final albedo calculation (back ground albedo, single vegetation scattering albedo, preferential direction of scattering); these parameters are computed from MODIS satellite observations. Juliane presented values per PFTs for each month. This need to be generalized given that the seasonal variation are not the same btw North and South hemisphere for instance.
    • Valentin B. raise the issue that the computation of an "Effective LAI" for the new RT scheme (compare to the "TRUE LAI") might change significantly the gross carbon production and that this need to be check carefully.
    • The inclusion of the "snow" in this new RT scheme needs to be though more deeply. For that we propose to have soon a meeting with C. Ottle for a summary on the current developments of a new snow module for ORC and to discuss the coupling with the RT scheme.
    • The treatment of Grasses still needs to be done.

Note finally that Juliane is planning to first validate and publish the new RT scheme with FM module in a stand alone mode.

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