CNNFixation

INTERFACE:

 subroutine CNNFixation(num_soilc, filter_soilc)

DESCRIPTION:

On the radiation time step, update the nitrogen fixation rate as a function of annual total NPP. This rate gets updated once per year. All N fixation goes to the soil mineral N pool.

USES:

    use clmtype
    use clm_varctl      , only: iulog
    use clm_time_manager, only: get_days_per_year
    use shr_sys_mod     , only: shr_sys_flush
    use clm_varcon      , only: secspday

ARGUMENTS:

    implicit none
    integer, intent(in) :: num_soilc       ! number of soil columns in filter
    integer, intent(in) :: filter_soilc(:) ! filter for soil columns

CALLED FROM:

   subroutine CNEcosystemDyn, in module CNEcosystemDynMod.F90

REVISION HISTORY:

   6/1/04: Created by Peter Thornton
   2/14/05, PET: After looking at a number of point simulations,
                 it looks like a constant Nfix might be more efficient and 
                 maybe more realistic - setting to constant 0.4 gN/m2/yr.

LOCAL VARIABLES:

   local pointers to implicit in scalars
    real(r8), pointer :: cannsum_npp(:) ! nitrogen deposition rate (gN/m2/s)
   local pointers to implicit out scalars
    real(r8), pointer :: nfix_to_sminn(:)
   !OTHER LOCAL VARIABLES:
    integer  :: c,fc                  ! indices
    real(r8) :: t                     ! temporary
    real(r8) :: dayspyr               ! days per year