CASAPot_Evptr

INTERFACE:

   subroutine CASAPot_Evptr(lbp, ubp, num_soilp, filter_soilp)

DESCRIPTION:

Potential Evapotranspiration Priestely-Taylor Equation Baldocchi et al. (2000): Climate and vegetation controls on boreal zone energy exchange. Global Change Biology, 6, (Suppl. 1), 69-83.

In Baldocchi et al, PET (equilibrium evaporation) is calculated for time step - as he compares the instantaneous evapotranspiration to the eqm evapotranspiration. I think that this is simplest, and avoids the definition of an averaging period. iyf 2002/05/09

The following calculation is done at every land point. No explicit discrimination among veg type or soil type Local ecology is implictly dealt with in the energy fluxes.

************************************************************************* the model partitions the latent heat flux into three components: o fcev: evaporation of intercepted water o fctr: transpiration o fgev: soil evaporation or snow sublimation

the model conserves surface energy fluxes as: o -fsa + fira + fsh + (fcev+fctr+fgev) + fcst + fgr + fsm = 0 o fsa + fsr = [solad(1)+solad(2)+solai(1)+solai(2)] = total incident solar o fira = -firgcm + fire currently canopy heat storage fcst = 0

------------ code history -------------- pot_evptr.F - From Inez modified for LSM/CASA interface by J.John (2002) ---------------------------------

ARGUMENTS:

     implicit none
     integer, intent(in) :: lbp, ubp      ! pft bounds
     integer, intent(in) :: num_soilp     ! number of soil points in pft filter
     integer, intent(in) :: filter_soilp(ubp-lbp+1) ! pft filter for soil points

LOCAL VARIABLES:

     integer  :: f                   ! filter index
     integer  :: g                   ! gridcell index
     integer  :: p                   ! pft index
     real(r8) :: qstar_net, q_grd, flh
     real(r8) :: tdegC, tadd, e_s, s, gamma, Q_E, factor, a_psy
     real(r8) :: fcst                        !canopy heat storage (w/m**2)
 
     ! inputs:
 
     integer , pointer :: pgridcell(:)      ! gridcell index of corresponding pft
     real(r8), pointer :: t_ref2m(:)        !2m surface air temperature (K)
     real(r8), pointer :: forc_pbot(:)      !atmospheric pressure (Pa)
     real(r8), pointer :: fsa(:)            !absorbed solar radiation (w/m**2)
     real(r8), pointer :: eflx_lwrad_net(:) !net infrared (longwave) rad (w/m**2) [+ = to atm]
     real(r8), pointer :: eflx_sh_tot(:)    !sensible heat flux (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_grnd(:)   !ground evaporation heat flux (w/m**2) [+ to atm]
     real(r8), pointer :: eflx_lh_vegt(:)   !veg transpiration heat flux (w/m**2) [+ to atm]
 
     !  outputs:
 
     real(r8), pointer :: pet(:)            !potential evaporation (mm h2o/s)

CALLED FROM:

   Casa in CASAMod

REVISION HISTORY:

   2004.06.08 Vectorized and reformatted by Forrest Hoffman