== Technical modifications ==


This page summarizes the choices and the modifications done for the externalization of the parameters.

=== Global Specifications ===

We tried to respect as soon as possible the structure of the code. Three folders over five were affected by
the modifications : ''src_parameters'', ''src_sechiba'' and ''src_stomate''. We regroup all the
files containing parameters in src_parameters. We rewrite some parts of the code in order not to have explicit
references to indexes to some PFTs (like agricultural ones). [[BR]]
We delete all the multiple definitions of some parameters like pi or the terrestrial radius R_Earth.


Finally, we gave names to some coefficents intervening in equations and externalized them.

 
The main changing are detailed below :


=== Src_parameters ===

Originally, this folder was organized in 4 files called '''constantes.f90''', '''constantes_co2.f90''', '''constantes_veg.f90''' and 
'''constantes_soil.f90'''. 

The last three files were mixed up with '''stomate_constants.f90''' to give '''pft_parameters.f90''' and '''constantes_mtc.f90'''. These new files make the initialization and the overwriting of the pft-parameters.

All the default values for the pft-parameters are in '''constantes_mtc.f90'''. 

'''constantes.f90''' contains all the physical constants used by ORCHIDEE 
and (for the moment) the rest of the externalized parameters (scalar and no-pfts-sized arrays).


=== Src_sechiba ===

We add a new module called '''qsat_moisture.f90'''. This module regroups the routines for the calculation of qsat (previously in '''constantes_veg.f90'''). [[BR]]
'''intersurf.f90''' reads the number of PFTs and the parameters values chosen by the user. 


=== Src_stomate ===

We delete '''stomate_constants.f90''' in order to move its parameters in ''src_parameters''. The too-specific parameters were moved to '''stomate_data.f90'''. [[BR]]
During our validations on fluxnet sites, we modified the herbivory model and the formulation for the variable 
"black_carbon". In '''stomate_season.f90''', we replace : 
{{{
    DO j = 2,nvm
       !
       IF ( natural(j) ) THEN
          !
          WHERE ( nlflong_nat(:) .GT. zero )
             consumption(:) = hvc1 * nlflong_nat(:) ** hvc2
             herbivores(:,j) = one_year * green_age(:) * nlflong_nat(:) / consumption(:)
          ELSEWHERE
             herbivores(:,j) = 100000.
          ENDWHERE
          !
       ELSE
          !
          herbivores(:,j) = 100000.
          !
       ENDIF
       !
    ENDDO
}}}
by : 
{{{
     DO j = 2,nvm
       !
       IF ( natural(j) ) THEN
          !
          WHERE ( nlflong_nat(:,j) .GT. zero )
             consumption(:) = hvc1 * nlflong_nat(:,j) ** hvc2
             herbivores(:,j) = one_year * green_age(:,j) * nlflong_nat(:,j) / consumption(:)
          ELSEWHERE
             herbivores(:,j) = 100000.
          ENDWHERE
          !
       ELSE
          !
          herbivores(:,j) = 100000.
          !
       ENDIF
       !
    ENDDO  
}}}
in order to make herbivores more pft-specific. For "black_carbon", we relaced the following line
{{{
 black_carbon(:) = &
                  black_carbon(:) + bcfrac(:) * residue(:) 
}}}
by :

{{{
 black_carbon(:) = &
                  black_carbon(:) + bcfrac(:) * residue(:) * veget_max(:,j)
}}}

In both cases, when we add a new PFT on the same surface, the consumption of herbivory and the quantity of black carbon was doubled ! That's why we change the formulations of these
two sub-models.