Changes between Version 51 and Version 52 of DevelopmentActivities/CMIP6/DevelopmentsCMIP6/soil_physic


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Timestamp:
10/07/15 11:05:03 (5 years ago)
Author:
peylin
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  • DevelopmentActivities/CMIP6/DevelopmentsCMIP6/soil_physic

    v51 v52  
    99    Current version of Fuxing is 8 Meters for both E and W, with same discretization. 
    1010    Questions: AD and JP wonder about the impact on the runoff and thus river discharges and possibly the time required for the spin up (such time is likely to increase with a 8 m soil) ?  
    11   - Modify the coupling of the new  multi-layer snow with soil to be fully implicit. => date ? 
    12     The current version in MICT works (couple and force mode) but is not fully implicit and the energy conservation at each time step should be checked!  
    13     The work to make it fully implicit needs to be quantified with Tao (Anticipated to be relatively straightforward) 
    1411  - Eventually implement a soil freezing for the "thin layers of the new vertical discretization" => ?? 
    1512    A solution to avoid large oscillations needs to be proposed and tested. 
    16   - Improve the albedo of the vegetation and bare soil: Work that can be pushed by a Post-doc from the CMUG project (Patricia is responsible of the project; person to be recruited); => Aout 2015;  
    17     propositions: Make some tests with the We can  try to re-activate the dependance of bare soil albedo to sol humidy with the 11 layers scheme. 
     13  
    1814 - Remarks : The agreement and the details of such roadmap should be done; Most likely we need to separate the different TASKs with a different group of people for each?  
    1915 
     
    395391Note that proposed scheme includes what Fuxing has implemented so far and allow to account for deep permafrost layering as done in MICT 
    396392 
    397 == Snow coupling == 
    398  
    399 === Presentation by Catherine and Tao (MICT version) ===  
    400  
    401 We had time only for a short presentation of the new snow module implementation: [https://forge.ipsl.jussieu.fr/orchidee/attachment/wiki/Meetings/CMIP6/Physic/Orchidee_snow_CMIP6.pdf​​][[BR]] 
    402  
    403 Some features : 
    404  
    405  - the number of layers of snow module (ES) is always 3 
    406  - when there is a snow fall the whole grid is covered by snow ; only the albedo is calculated with a fractional snow cover (standard linear fractional cover) 
    407  - After "Enerbil" the "ES" module update the snow temp profile and accounts for melt, freezing, sublimation,... It then computes the coeficient for the next time step that is given to "Enerbil": the equivalent capacity "C" term that account in an implicit way the ground heat flux (here the flux through the snow pack); Then he provides "Thermosoil" with the lowest snow layer temperature. Thermosoil use that temperature to update its temperature profile and provide back a surface flux for "ES" for the next time step. 
    408  - It seems thus that the scheme is not fully implicit with respect to the "flux from ground to the snow" that is provided in an explicit way from the previous time step value.  
    409  - With the coupled simulation, Tao had to define a minimum snow depth (1 cm ?) to avoid "crashes"; possible problem of energy conservation ? 
    410  
    411 === Discussion === 
    412  
    413 We discussed the potential impact of the non fully implicit "soil-snow-atm" scheme. Catherine mentionned that in ISBA, Aaron B. had similar issues and that the change to fully implicit did not impacted much the results. 
    414  
    415 However, we agreed that with very thin snow layers this could be a problem (see "trick" of Tao in coupled mode).  
    416  
    417 We  proposed that a first improvement is to account for fractional snow cover for the energy budget (not only for the albedo). For that the equavalent "C" term passed to "Enerbil" should be a mix between the standard one of "Thermosoil" and the one from "ES". But this needs some revision of the equation and calls of the routine (to be writen explicitely first). 
    418  
    419 JP propose that we also split the fluxes from Thermosoil back to enerbil and ES with different values.. this would ensure also a full implicit scheme.  
    420  
    421393 
    422394== PROPOSED ACTIONS == 
     
    429401  - FOR CMIP6: we propose to start with version V3 of Fuxing unless new tests show that V2 is better; we also proposed to use new USDA soil texture classes. 
    430402  - Remark on the W depth: in CMIP5 the depth of choisnel was increase to avoid Amazon drying; this should not be the case with the 2m CWRR as there are much more water holding capacity than with Choisnel. BUT we keep in mind the possibility to increase Depth_Wmax 
    431  - Snow Scheme: 
    432   - Josefine with Tao will implement the updated version of ES (currently in MICT) into TRUNC 
    433   - We then further add a fractional snow cover so that the problem of "very thin" snow layer (linked to the non fully implicit scheme) becomes most likely negligeable. FOR THAT, we need to start an email discussion about the requested changes (how does it change the call sequences to "thermosoil" and "ES" ?): Anyone is wellcome to launch the email discussion. Then, JLD propose that Fuxing helps with this implementation but other organizations are possible.  
    434   - Few persons needs to gather to establish properly the equation-changes that are needed for a full implicit implementation between "enerbyl" "ES" and "Thermosoil": the list of the "few" needs to be decided ? (volunter ?) 
     403 
    435404 - Soil freezing 
    436405  - We start for CMIP6 with the current scheme of Isabelle G. 
     
    568537 It has been corrected. Now the unit of SWE is the same with that of ORCHIDEE standard output (Kg/m²). [[BR]] 
    569538 
    570 == Testing roughness length for heat in LMDZOR == 
    571  
    572 01-Sep-2015 by Fuxing WANG, Frederique CHERUY. [[BR]] 
    573  
    574 Background: 
    575     The roughness length for heat (z0h) is generally not identical to roughness length for momentum (z0m). [[BR]] 
    576     In LMDZOR, z0h = z0m. A short description of related code is (only in coupled mode): https://forge.ipsl.jussieu.fr/orchidee/attachment/wiki/Meetings/CMIP6/Physic/condveg_z0cdrag.pdf [[BR]] 
    577 Objective: 
    578     To test the sensitively of LMDZOR to z0h.[[BR]] 
    579 Simulations: 
    580     Two simulations (1-year) were done with LMDZOR after 20 years spin-up.[[BR]] 
    581     (1) CTL: z0h = z0m; ORCHIDEE-rev 2664, LMDZ-rev 2287; new soil vertical discretization and soil thermodynamics [[BR]] 
    582     (2) EXP: The same as CTL, but z0h = 0.1 * z0m. [[BR]] 
    583 Results:  
    584     Results are compared over different seasons (annual mean, JJA and DJF): https://forge.ipsl.jussieu.fr/orchidee/attachment/wiki/Meetings/CMIP6/Physic/z0mh_annual_jja_djf.pdf. [[BR]] 
    585     The left side in the figures is "CTL: z0h = z0m", the right side is the 'EXP-CTL' (except the last row which is the " EXP/CTL"). [[BR]] 
    586     The Ts (temp_sol) increases over most regions. The maximum increase is over 0N-90N in JJA (1-2K), while it is over 30N-60S in DJF (0.5-1.5K).(Fig b) [[BR]] 
    587     The pattern of fluxsens is similar for different seasons. It increases over most regions (3 W/m2 for most regions).[[BR]] 
    588     The variation of fluxlat (+/- 6 W/m2 over most regions) and precipitation (+/-0.5mm/d over most regions) is less systematic than Ts and fluxsens. [[BR]] 
     539