#include <misc.h>#include <preproc.h>subroutine Hydrology1 (clm)!-----------------------------------------------------------------------!!  CLMCLMCLMCLMCLMCLMCLMCLMCLMCL  A community developed and sponsored, freely!  L                           M  available land surface process model.!  M --COMMUNITY LAND MODEL--  C!  C                           L!  LMCLMCLMCLMCLMCLMCLMCLMCLMCLM!!-----------------------------------------------------------------------! Purpose:! Calculation of ! (1) water storage of intercepted precipitation! (2) direct throughfall and canopy drainage of precipitation! (3) the fraction of foliage covered by water and the fraction!     of foliage that is dry and transpiring. ! (4) snow layer initialization if the snow accumulation exceeds 10 mm.!! Note:  The evaporation loss is taken off after the calculation of leaf ! temperature in the subroutine clm_leaftem.f90, not in this subroutine.!! Method:!! Author:! 15 September 1999: Yongjiu Dai; Initial code! 15 December 1999:  Paul Houser and Jon Radakovich; F90 Revision ! April 2002: Vertenstein/Oleson/Levis; Final form!-----------------------------------------------------------------------! $Id: Hydrology1.F90,v 1.4.2.2 2002/04/27 15:38:38 erik Exp $!-----------------------------------------------------------------------  use precision  use clmtype  use clm_varcon, only : tfrz, istice, istwet, istsoil  implicit none!----Arguments----------------------------------------------------------  type (clm1d), intent(inout) :: clm        !CLM 1-D Module!----Local Variables----------------------------------------------------  integer newnode       ! flag when new snow node is set, (1=yes, 0=no)  real(r8) prcp         ! precipitation rate [mm/s]  real(r8) h2ocanmx     ! maximum allowed water on canopy [mm]  real(r8) fpi          ! coefficient of interception [-]  real(r8) xrun         ! water that exceeds the leaf capacity [mm/s]  real(r8) qflx_candrip ! rate of canopy runoff and snow falling off canopy [mm/s]  real(r8) qflx_through ! direct throughfall [mm/s]  real(r8) dz_snowf     ! layer thickness rate change due to precipitation [mm/s]  real(r8) flfall       ! fraction of liquid water within falling precip. [-]  real(r8) bifall       ! bulk density of newly fallen dry snow [kg/m3]  real(r8) coefb        ! Slope of "Alta" expression for dependence of flfall on temp  real(r8) coefa        ! Offset of "Alta" expression for dependence of flfall on temp!----End Variable List--------------------------------------------------!! [1] Canopy interception and precipitation onto ground surface!!! [1.1] Add precipitation to leaf water !  if (clm%itypwat==istsoil .OR. clm%itypwat==istwet) then     qflx_candrip = 0.                 ! rate of canopy runoff     qflx_through = 0.                 ! precipitation direct through canopy     clm%qflx_prec_intr = 0.           ! intercepted precipitation       prcp = clm%forc_rain + clm%forc_snow  ! total precipitation     if (clm%frac_veg_nosno == 1 .AND. prcp > 0.) then!! The leaf water capacities for solid and liquid are different, ! generally double for snow, but these are of somewhat less significance! for the water budget because of lower evap. rate at lower temperature.! Hence, it is reasonable to assume that vegetation storage of solid water ! is the same as liquid water.!        h2ocanmx = clm%dewmx * (clm%elai + clm%esai)!! Direct throughfall!        fpi = 1. - exp(-0.5*(clm%elai + clm%esai))        qflx_through  = prcp*(1.-fpi)!! Water storage of intercepted precipitation and dew!        clm%qflx_prec_intr = prcp*fpi        clm%h2ocan = max(0._r8, clm%h2ocan + clm%dtime*clm%qflx_prec_intr)!! Initialize rate of canopy runoff and snow falling off canopy!        qflx_candrip = 0.0!! Water that exceeds the leaf capacity!        xrun = (clm%h2ocan - h2ocanmx)/clm%dtime!! Test on maximum dew on leaf!        if (xrun > 0.) then           qflx_candrip = xrun           clm%h2ocan = h2ocanmx        endif     endif  else if (clm%itypwat == istice) then     clm%qflx_prec_intr = 0.     clm%h2ocan = 0.     qflx_candrip = 0.     qflx_through = 0.    endif!! [1.2] Precipitation onto ground (kg/(m2 s))!  if (clm%frac_veg_nosno == 0) then     clm%qflx_prec_grnd = clm%forc_rain + clm%forc_snow  else     clm%qflx_prec_grnd = qflx_through + qflx_candrip    endif  !! [1.3] The percentage of liquid water by mass is arbitrarily set to !       vary linearly with air temp, from 0% at 273.16 to 40% max at 275.16.!  if (clm%itypprc <= 1) then     flfall = 1.               ! fraction of liquid water within falling precip     if (clm%do_capsnow) then        clm%qflx_snowcap = clm%qflx_prec_grnd        clm%qflx_snow_grnd = 0.        clm%qflx_rain_grnd = 0.     else        clm%qflx_snowcap = 0.        clm%qflx_snow_grnd = 0.                  ! ice onto ground (mm/s)        clm%qflx_rain_grnd = clm%qflx_prec_grnd  ! liquid water onto ground (mm/s)     endif     dz_snowf = 0.             ! rate of snowfall, snow depth/s (m/s)  else#if (defined PERGRO)     coefb = 0.4/2.0     coefa = -coefb*tfrz     if (clm%forc_t <= tfrz) then        flfall = 0.0     else if (clm%forc_t <= tfrz+2.) then        flfall = coefa + coefb*clm%forc_t     else        flfall = coefa + coefb*(tfrz+2.)     endif#else     if (clm%forc_t <= tfrz) then        flfall = 0.     else if (clm%forc_t <= tfrz+2.) then        flfall = -54.632 + 0.2*clm%forc_t     else        flfall = 0.4     endif#endif     !! Use Alta relationship, Anderson(1976); LaChapelle(1961), ! U.S.Department of Agriculture Forest Service, Project F, ! Progress Rep. 1, Alta Avalanche Study Center:Snow Layer Densification.!#if (defined PERGRO)     if (clm%forc_t > tfrz + 2.) then        bifall=50. + 1.7*(17.0)**1.5     else if (clm%forc_t > tfrz - 15.) then        bifall=50. + 1.7*(clm%forc_t - tfrz + 15.)**1.5     else        bifall=50.     endif#else     if (clm%forc_t > tfrz + 2.) then        bifall =189.     else if (clm%forc_t > tfrz - 15.) then        bifall=50. + 1.7*(clm%forc_t - tfrz + 15.)**1.5     else        bifall=50.     endif#endif          if (clm%do_capsnow) then        clm%qflx_snowcap = clm%qflx_prec_grnd        clm%qflx_snow_grnd = 0.        clm%qflx_rain_grnd = 0.        dz_snowf = 0.     else        clm%qflx_snowcap = 0.        clm%qflx_snow_grnd = clm%qflx_prec_grnd*(1.-flfall)                         clm%qflx_rain_grnd = clm%qflx_prec_grnd*flfall        dz_snowf = clm%qflx_snow_grnd/bifall                        clm%snowdp = clm%snowdp + dz_snowf*clm%dtime                 clm%h2osno = clm%h2osno + clm%qflx_snow_grnd*clm%dtime     endif     if (clm%itypwat==istwet .AND. clm%t_grnd>tfrz) then        clm%h2osno=0.         clm%snowdp=0.         clm%snowage=0.     endif  endif!! [2] Determine the fraction of foliage covered by water and the !     fraction of foliage that is dry and transpiring.!  call Fwet(clm)!! [3] When the snow accumulation exceeds 10 mm, initialize snow layer.!     Currently, the water temperature for the precipitation is simply set !     to the surface air temperature.!  newnode = 0    ! flag for when snow node will be initialized  if (clm%snl == 0 .AND. clm%qflx_snow_grnd > 0.0 .AND. clm%snowdp >= 0.01) then     newnode = 1     clm%snl = -1     clm%dz(0) = clm%snowdp                       ! meter     clm%z(0) = -0.5*clm%dz(0)     clm%zi(-1) = -clm%dz(0)     clm%snowage = 0.                             ! snow age     clm%t_soisno (0) = min(tfrz, clm%forc_t)     ! K     clm%h2osoi_ice(0) = clm%h2osno               ! kg/m2     clm%h2osoi_liq(0) = 0.                       ! kg/m2     clm%frac_iceold(0) = 1.  endif!! The change of ice partial density of surface node due to precipitation.! Only ice part of snowfall is added here, the liquid part will be added later!  if (clm%snl < 0 .AND. newnode == 0) then     clm%h2osoi_ice(clm%snl+1) = clm%h2osoi_ice(clm%snl+1)+clm%dtime*clm%qflx_snow_grnd     clm%dz(clm%snl+1) = clm%dz(clm%snl+1)+dz_snowf*clm%dtime  endifend subroutine Hydrology1!========================================================================subroutine Fwet(clm)  use precision  use clmtype  implicit none!=== Arguments ===========================================================  type (clm1d), intent(inout) :: clm        !CLM 1-D Module!=== Local Variables =====================================================! fwet is the fraction of all vegetation surfaces which are wet ! including stem area which contribute to evaporation.! fdry is the fraction of elai which is dry because only leaves! can transpire.  Adjusted for stem area which does not transpire.  real(r8) vegt             ! frac_veg_nosno*lsai  real(r8) dewmxi           ! inverse of maximum allowed dew [1/mm]!=== End Variable List ===================================================  if (clm%frac_veg_nosno == 1) then     if (clm%h2ocan > 0.) then        vegt     = clm%frac_veg_nosno*(clm%elai + clm%esai)        dewmxi   = 1.0/clm%dewmx        clm%fwet = ((dewmxi/vegt)*clm%h2ocan)**.666666666666        clm%fwet = min (clm%fwet,1.0_r8)     ! Check for maximum limit of fwet     else        clm%fwet = 0.     endif     clm%fdry = (1.-clm%fwet)*clm%elai/(clm%elai+clm%esai)#if (defined PERGRO)     clm%fwet = 0.     clm%fdry = clm%elai/(clm%elai+clm%esai)#endif  else     clm%fwet = 0.     clm%fdry = 0.  endifend subroutine Fwet