Changes between Version 34 and Version 35 of DevelopmentActivities/CMIP6/DevelopmentsCMIP6/soil_physic

Timestamp:

2015-02-27T16:17:13+01:00 (9 years ago)

Author:

peylin

Comment:

--

DevelopmentActivities/CMIP6/DevelopmentsCMIP6/soil_physic

@@ -402 +402 @@
  - the number of layers of snow module (ES) is always 3
  - 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)
- - 
- - With the coupled simulation, Tao had to define a minimum snow depth (1 cm ?) to avoid "crashes"
+ - 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.
+ - 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. 
+ - With the coupled simulation, Tao had to define a minimum snow depth (1 cm ?) to avoid "crashes"; possible problem of energy conservation ?
 
 === Discussion ===
- 
+
+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.
+
+However, we agreed that with very thin snow layers this could be a problem (see "trick" of Tao in coupled mode). 
+
+We thus proposed that a first improvement could be 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 one from standard "Thermosoil" 
 
 == PROPOSED ACTIONS ==