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### CanopyFluxes

INTERFACE:

```   subroutine CanopyFluxes(lbg, ubg, lbc, ubc, lbp, ubp, &
num_nolakep, filter_nolakep)
```
DESCRIPTION:

1. Calculates the leaf temperature: 2. Calculates the leaf fluxes, transpiration, photosynthesis and updates the dew accumulation due to evaporation.

Method: Use the Newton-Raphson iteration to solve for the foliage temperature that balances the surface energy budget:

f(t_veg) = Net radiation - Sensible - Latent = 0 f(t_veg) + d(f)/d(t_veg) * dt_veg = 0 (*)

Note: (1) In solving for t_veg, t_grnd is given from the previous timestep. (2) The partial derivatives of aerodynamical resistances, which cannot be determined analytically, are ignored for d(H)/dT and d(LE)/dT (3) The weighted stomatal resistance of sunlit and shaded foliage is used (4) Canopy air temperature and humidity are derived from => Hc + Hg = Ha => Ec + Eg = Ea (5) Energy loss is due to: numerical truncation of energy budget equation (*); and "ecidif" (see the code) which is dropped into the sensible heat (6) The convergence criteria: the difference, del = t_veg(n+1)-t_veg(n) and del2 = t_veg(n)-t_veg(n-1) less than 0.01 K, and the difference of water flux from the leaf between the iteration step (n+1) and (n) less than 0.1 W/m2; or the iterative steps over 40.

USES:

```     use shr_kind_mod       , only : r8 => shr_kind_r8
use clmtype
use clm_atmlnd         , only : clm_a2l
use clm_time_manager   , only : get_step_size, get_prev_date
use clm_varpar         , only : nlevgrnd, nlevsno
use clm_varcon         , only : sb, cpair, hvap, vkc, grav, denice, &
denh2o, tfrz, csoilc, tlsai_crit, alpha_aero, &
isecspday, degpsec
use shr_const_mod      , only : SHR_CONST_TKFRZ
use pftvarcon          , only : nirrig
use QSatMod            , only : QSat
use FrictionVelocityMod, only : FrictionVelocity, MoninObukIni
use spmdMod            , only : masterproc
```
ARGUMENTS:
```     implicit none
integer, intent(in) :: lbg, ubg                    ! gridcell bounds
integer, intent(in) :: lbc, ubc                    ! column bounds
integer, intent(in) :: lbp, ubp                    ! pft bounds
integer, intent(in) :: num_nolakep                 ! number of column non-lake points in pft filter
integer, intent(in) :: filter_nolakep(ubp-lbp+1)   ! pft filter for non-lake points
```
CALLED FROM:
```   subroutine Biogeophysics1 in module Biogeophysics1Mod
```
REVISION HISTORY:
```   15 September 1999: Yongjiu Dai; Initial code
15 December 1999:  Paul Houser and Jon Radakovich; F90 Revision
12/19/01, Peter Thornton
Changed tg to t_grnd for consistency with other routines
1/29/02, Peter Thornton
Migrate to new data structures, new calling protocol. For now co2 and
o2 partial pressures are hardwired, but they should be coming in from
forc_pco2 and forc_po2. Keeping the same hardwired values as in CLM2 to
assure bit-for-bit results in the first comparisons.
27 February 2008: Keith Oleson; Sparse/dense aerodynamic parameters from
X. Zeng
6 March 2009: Peter Thornton; Daylength control on Vcmax, from Bill Bauerle
```
LOCAL VARIABLES:
```   local pointers to implicit in variables
integer , pointer :: frac_veg_nosno(:) ! frac of veg not covered by snow (0 OR 1 now) [-]
integer , pointer :: ivt(:)         ! pft vegetation type
integer , pointer :: pcolumn(:)     ! pft's column index
integer , pointer :: plandunit(:)   ! pft's landunit index
integer , pointer :: pgridcell(:)   ! pft's gridcell index
real(r8), pointer :: forc_th(:)     ! atmospheric potential temperature (Kelvin)
real(r8), pointer :: t_grnd(:)      ! ground surface temperature [K]
real(r8), pointer :: thm(:)         ! intermediate variable (forc_t+0.0098*forc_hgt_t_pft)
real(r8), pointer :: qg(:)          ! specific humidity at ground surface [kg/kg]
real(r8), pointer :: thv(:)         ! virtual potential temperature (kelvin)
real(r8), pointer :: z0mv(:)        ! roughness length over vegetation, momentum [m]
real(r8), pointer :: z0hv(:)        ! roughness length over vegetation, sensible heat [m]
real(r8), pointer :: z0qv(:)        ! roughness length over vegetation, latent heat [m]
real(r8), pointer :: z0mg(:)        ! roughness length of ground, momentum [m]
real(r8), pointer :: dqgdT(:)       ! temperature derivative of "qg"
real(r8), pointer :: htvp(:)        ! latent heat of evaporation (/sublimation) [J/kg]
real(r8), pointer :: emv(:)         ! ground emissivity
real(r8), pointer :: emg(:)         ! vegetation emissivity
real(r8), pointer :: forc_pbot(:)   ! atmospheric pressure (Pa)
real(r8), pointer :: forc_pco2(:)   ! partial pressure co2 (Pa)
#if (defined C13)
! 4/14/05: PET
real(r8), pointer :: forc_pc13o2(:) ! partial pressure c13o2 (Pa)
#endif

real(r8), pointer :: forc_po2(:)    ! partial pressure o2 (Pa)
real(r8), pointer :: forc_q(:)      ! atmospheric specific humidity (kg/kg)
real(r8), pointer :: forc_u(:)      ! atmospheric wind speed in east direction (m/s)
real(r8), pointer :: forc_v(:)      ! atmospheric wind speed in north direction (m/s)
real(r8), pointer :: forc_hgt_u_pft(:) !observational height of wind at pft level [m]
real(r8), pointer :: forc_rho(:)    ! density (kg/m**3)
real(r8), pointer :: displa(:)      ! displacement height (m)
real(r8), pointer :: elai(:)        ! one-sided leaf area index with burying by snow
real(r8), pointer :: esai(:)        ! one-sided stem area index with burying by snow
real(r8), pointer :: fdry(:)        ! fraction of foliage that is green and dry [-]
real(r8), pointer :: fwet(:)        ! fraction of canopy that is wet (0 to 1)
real(r8), pointer :: laisun(:)      ! sunlit leaf area
real(r8), pointer :: laisha(:)      ! shaded leaf area
real(r8), pointer :: sabv(:)        ! solar radiation absorbed by vegetation (W/m**2)
real(r8), pointer :: watsat(:,:)    ! volumetric soil water at saturation (porosity)
real(r8), pointer :: watdry(:,:)    ! btran parameter for btran=0
real(r8), pointer :: watopt(:,:)    ! btran parameter for btran = 1
real(r8), pointer :: h2osoi_ice(:,:)! ice lens (kg/m2)
real(r8), pointer :: h2osoi_liq(:,:)! liquid water (kg/m2)
real(r8), pointer :: dz(:,:)        ! layer depth (m)
real(r8), pointer :: t_soisno(:,:)  ! soil temperature (Kelvin)
real(r8), pointer :: sucsat(:,:)    ! minimum soil suction (mm)
real(r8), pointer :: bsw(:,:)       ! Clapp and Hornberger "b"
real(r8), pointer :: rootfr(:,:)    ! fraction of roots in each soil layer
real(r8), pointer :: dleaf(:)       ! characteristic leaf dimension (m)
real(r8), pointer :: smpso(:)       ! soil water potential at full stomatal opening (mm)
real(r8), pointer :: smpsc(:)       ! soil water potential at full stomatal closure (mm)
real(r8), pointer :: frac_sno(:)    ! fraction of ground covered by snow (0 to 1)
real(r8), pointer :: htop(:)        ! canopy top(m)
real(r8), pointer :: snowdp(:)      ! snow height (m)
real(r8), pointer :: soilbeta(:)    ! soil wetness relative to field capacity
real(r8), pointer :: lat(:)         ! latitude (radians)
real(r8), pointer :: decl(:)        ! declination angle (radians)
real(r8), pointer :: max_dayl(:)    !maximum daylength for this column (s)
real(r8), pointer :: londeg(:)      ! longitude (degrees) (for calculation of local time)

local pointers to implicit inout arguments
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 :: t_veg(:)       ! vegetation temperature (Kelvin)
real(r8), pointer :: t_ref2m(:)     ! 2 m height surface air temperature (Kelvin)
real(r8), pointer :: q_ref2m(:)     ! 2 m height surface specific humidity (kg/kg)
real(r8), pointer :: t_ref2m_r(:)   ! Rural 2 m height surface air temperature (Kelvin)
real(r8), pointer :: rh_ref2m(:)    ! 2 m height surface relative humidity (%)
real(r8), pointer :: rh_ref2m_r(:)  ! Rural 2 m height surface relative humidity (%)
real(r8), pointer :: h2ocan(:)      ! canopy water (mm H2O)
real(r8), pointer :: cisun(:)       !sunlit intracellular CO2 (Pa)
real(r8), pointer :: cisha(:)       !shaded intracellular CO2 (Pa)
local pointers to implicit out arguments
real(r8), pointer :: rb1(:)             ! boundary layer resistance (s/m)
real(r8), pointer :: cgrnd(:)           ! deriv. of soil energy flux wrt to soil temp [w/m2/k]
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 :: ram1(:)            ! aerodynamical resistance (s/m)
real(r8), pointer :: btran(:)           ! transpiration wetness factor (0 to 1)
real(r8), pointer :: rssun(:)           ! sunlit stomatal resistance (s/m)
real(r8), pointer :: psnsun(:)          ! sunlit leaf photosynthesis (umol CO2 /m**2/ s)
real(r8), pointer :: psnsha(:)          ! shaded leaf photosynthesis (umol CO2 /m**2/ s)
#if (defined C13)
! 4/14/05: PET
real(r8), pointer :: c13_psnsun(:)      ! sunlit leaf photosynthesis (umol 13CO2 /m**2/ s)
real(r8), pointer :: c13_psnsha(:)      ! shaded leaf photosynthesis (umol 13CO2 /m**2/ s)
! 4/21/05: PET
real(r8), pointer :: rc13_canair(:)     !C13O2/C12O2 in canopy air
real(r8), pointer :: rc13_psnsun(:)     !C13O2/C12O2 in sunlit canopy psn flux
real(r8), pointer :: rc13_psnsha(:)     !C13O2/C12O2 in shaded canopy psn flux
real(r8), pointer :: alphapsnsun(:)     !fractionation factor in sunlit canopy psn flux
real(r8), pointer :: alphapsnsha(:)     !fractionation factor in shaded canopy psn flux
#endif

real(r8), pointer :: qflx_tran_veg(:)   ! vegetation transpiration (mm H2O/s) (+ = to atm)
real(r8), pointer :: dt_veg(:)          ! change in t_veg, last iteration (Kelvin)
real(r8), pointer :: qflx_evap_veg(:)   ! vegetation evaporation (mm H2O/s) (+ = to atm)
real(r8), pointer :: eflx_sh_veg(:)     ! sensible heat flux from leaves (W/m**2) [+ to atm]
real(r8), pointer :: taux(:)            ! wind (shear) stress: e-w (kg/m/s**2)
real(r8), pointer :: tauy(:)            ! wind (shear) stress: n-s (kg/m/s**2)
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 :: fpsn(:)            ! photosynthesis (umol CO2 /m**2 /s)
real(r8), pointer :: rootr(:,:)         ! effective fraction of roots in each soil layer
real(r8), pointer :: rresis(:,:)        ! root resistance by layer (0-1)  (nlevgrnd)
real(r8), pointer :: irrig_rate(:)      ! current irrigation rate [mm/s]
integer, pointer  :: n_irrig_steps_left(:) ! # of time steps for which we still need to irrigate today
!OTHER LOCAL VARIABLES:
```

Next: Stomata Up: Fortran: Module Interface CanopyFluxesMod Previous: Fortran: Module Interface CanopyFluxesMod   Contents
Erik Kluzek 2011-06-15