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Differences between T_S, T_G and T_SNOW

Added by Sylvain Marchi 3 months ago

Dear CCLM-CLM users,
Our group has recently developed a fully-coupled ice-sheet - ocean -sea-ice - atmosphere - land model involving CCLM_CLM. Our configuration covers the Antarctic. I would like to know what are the differences between the following variables outputted by COSMO: T_S (temperature of surface), T_G (temperature at the boundary soil-atmosphere) and T_SNOW (temperature of snow surface). I did not find in the documentation how they are computed. I observe that T_S and T_G provide identical temperatures over the continental ice, but it is not true over the ocean (especially over the sea ice). I am also surprised to see differences up to 20°C in absolute value between T_S and T_SNOW (at most places, the surface is fully covered by snow).
Thank you very much for your input,
Sylvain


Replies (3)

RE: Differences between T_S, T_G and T_SNOW - Added by Burkhardt Rockel 3 months ago

I do not use the coupled version ans therefore have no experience how the parameters behave there. In the uncoupled version there is a sketch in the subroutine src_soil_multlay.f90:

!     Definition of temperature/water related variables in the soil model
!
!
!     --------------T_snow--------
!                                | 
!           fr_snow              |            1 - fr_snow
!                                |      
!     ______________T_s__________|________________T_s_____________
!     ////////////////////////////////////////////////////////////
!
!     Layer k=1 - - - - -  T_SO(k) , W_SO(k), W_SO_ICE(k) - - - -
!
!     ____________________________________________________________
!                                
!                                .
!                                .
!                                . 
!
!     ------------------------------------------------------------
!
!
!     Layer k=ke_soil+1 - - - (climate layer) - - - - - - - - - -
!
!
!     ____________________________________________________________
!
!
!
!     The surface temperature T_g is the snow fraction (fr_snow)
!     weighted sum of T_snow and T_s!
!==============================================================================

RE: Differences between T_S, T_G and T_SNOW - Added by Sylvain Marchi 3 months ago

Thanks for replying Burkhardt. Given that the surface temperature T_s is the snow fraction weighted sum of T_snow and T_s and that each model cell in Antarctica is almost 100% covered by snow, one can expect T_g to be close to T_s then?

RE: Differences between T_S, T_G and T_SNOW - Added by Burkhardt Rockel 3 months ago

Over areas covered 100% by snow I would expect T_G to be the same as T_SNOW. T_S is the temperature at the earth surface under the snow this can be much different than the temperature at the snow surface T_SNOW.

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