Biogeophysics2

INTERFACE:

   subroutine Biogeophysics2 (c)

DESCRIPTION:

   This is the main subroutine to execute the calculation of soil/snow and
   ground temperatures and update surface fluxes based on the new ground
   temperature 
   Calling sequence is:
   Biogeophysics2:                    surface biogeophysics driver
      -> SoilTemperature:             soil/snow and ground temperatures      
            -> SoilTermProp           thermal conductivities and heat 
                                       capacities        
            -> Tridiagonal            tridiagonal matrix solution            
            -> PhaseChange            phase change of liquid/ice contents        
   (1) Snow and soil temperatures
       o The volumetric heat capacity is calculated as a linear combination 
         in terms of the volumetric fraction of the constituent phases. 
       o The thermal conductivity of soil is computed from 
         the algorithm of Johansen (as reported by Farouki 1981), and the 
         conductivity of snow is from the formulation used in
         SNTHERM (Jordan 1991).
       o Boundary conditions:  
         F = Rnet - Hg - LEg (top),  F= 0 (base of the soil column).
       o Soil / snow temperature is predicted from heat conduction 
         in 10 soil layers and up to 5 snow layers. 
         The thermal conductivities at the interfaces between two 
         neighboring layers (j, j+1) are derived from an assumption that 
         the flux across the interface is equal to that from the node j 
         to the interface and the flux from the interface to the node j+1. 
         The equation is solved using the Crank-Nicholson method and 
         results in a tridiagonal system equation.
   (2) Phase change (see PhaseChange.F90)

USES:

     use clmtype
     use globals
     use clm_varcon, only : hvap, cpair, grav, vkc, tfrz, sb
     use clm_varpar, only : nlevsoi
     use SoilTemperatureMod

ARGUMENTS:

     implicit none
     type (column_type),target,intent(inout):: c		!column derived type

CALLED FROM:

   subroutine driver

REVISION HISTORY:

   15 September 1999: Yongjiu Dai; Initial code
   15 December 1999:  Paul Houser and Jon Radakovich; F90 Revision 
   Migrated to clm2.0 by Keith Oleson and Mariana Vertenstein
   Migrated to clm2.1 new data structures by Peter Thornton and M. Vertenstein

LOCAL VARIABLES:

   local pointers to implicit in arguments
     integer , pointer :: snl             !number of snow layers
     logical , pointer :: do_capsnow      !true => do snow capping
     real(r8), pointer :: forc_lwrad      !downward infrared (longwave) radiation (W/m**2)
     real(r8), pointer :: emg             !ground emissivity
     real(r8), pointer :: htvp            !latent heat of vapor of water (or sublimation) [j/kg]
     real(r8), pointer :: t_grnd          !ground temperature (Kelvin)
     integer , pointer :: frac_veg_nosno  !fraction of vegetation not covered by snow (0 OR 1 now) [-]
     real(r8), pointer :: cgrnds          !deriv, of soil sensible heat flux wrt soil temp [w/m2/k]
     real(r8), pointer :: cgrndl          !deriv of soil latent heat flux wrt soil temp [w/m**2/k]
     real(r8), pointer :: sabg            !solar radiation absorbed by ground (W/m**2)
     real(r8), pointer :: dlrad           !downward longwave radiation below the canopy [W/m2]
     real(r8), pointer :: ulrad           !upward longwave radiation above the canopy [W/m2]
     real(r8), pointer :: eflx_sh_veg     !sensible heat flux from leaves (W/m**2) [+ to atm]
     real(r8), pointer :: qflx_evap_veg   !vegetation evaporation (mm H2O/s) (+ = to atm)
     real(r8), pointer :: qflx_tran_veg   !vegetation transpiration (mm H2O/s) (+ = to atm)
     real(r8), pointer :: qflx_evap_can   !evaporation from leaves and stems (mm H2O/s) (+ = to atm)
   local pointers to implicit inout arguments
     real(r8), pointer :: eflx_sh_grnd    !sensible heat flux from ground (W/m**2) [+ to atm]
     real(r8), pointer :: qflx_evap_soi   !soil evaporation (mm H2O/s) (+ = to atm)
     real(r8), pointer :: qflx_snowcap    !excess precipitation due to snow capping (mm H2O /s)
   local pointers to implicit out arguments
     real(r8), pointer :: dt_grnd         !change in t_grnd, last iteration (Kelvin)
     real(r8), pointer :: eflx_soil_grnd  !soil heat flux (W/m**2) [+ = into soil]
     real(r8), pointer :: eflx_sh_tot     !total sensible heat flux (W/m**2) [+ to atm]
     real(r8), pointer :: qflx_evap_tot   !qflx_evap_soi + qflx_evap_veg + qflx_tran_veg
     real(r8), pointer :: eflx_lh_tot     !total latent heat flux (W/m8*2)  [+ to atm]
     real(r8), pointer :: qflx_evap_grnd  !ground surface evaporation rate (mm H2O/s) [+]
     real(r8), pointer :: qflx_sub_snow   !sublimation rate from snow pack (mm H2O /s) [+]
     real(r8), pointer :: qflx_dew_snow   !surface dew added to snow pack (mm H2O /s) [+]
     real(r8), pointer :: qflx_dew_grnd   !ground surface dew formation (mm H2O /s) [+]
     real(r8), pointer :: eflx_lwrad_out  !emitted infrared (longwave) radiation (W/m**2)
     real(r8), pointer :: eflx_lwrad_net  !net infrared (longwave) rad (W/m**2) [+ = to atm]
     real(r8), pointer :: eflx_lh_vege    !veg evaporation heat flux (W/m**2) [+ to atm]
     real(r8), pointer :: eflx_lh_vegt    !veg transpiration heat flux (W/m**2) [+ to atm]
     real(r8), pointer :: eflx_lh_grnd    !ground evaporation heat flux (W/m**2) [+ to atm]
     real(r8), pointer :: t_rad_pft       !pft-level radiative temperature (Kelvin)
     real(r8), pointer :: t_rad_column    !column-level radiative temperature (Kelvin)
     real(r8), pointer :: errsoi          !soil/lake energy conservation error (W/m**2)
   local pointers to implicit in scalars
     real(r8), pointer :: wt              !pft weight relative to column
   local pointers to implicit in arrays
     real(r8), dimension(:), pointer:: tssbef     !soil/snow temperature before update
     real(r8), dimension(:), pointer:: t_soisno   !soil temperature (Kelvin)
     real(r8), dimension(:), pointer:: h2osoi_ice !ice lens (kg/m2) (new)
     real(r8), dimension(:), pointer:: h2osoi_liq !liquid water (kg/m2) (new)