SUBROUTINE combo ( dz, wliq,  wice,  t, &                    dz2, wliq2, wice2, t2 )!=======================================================================!      Source file: combo.f90! Original version: Yongjiu Dai, September 15, 1999!! combines two elements and returns the following combined! variabless: dz, t, wliq, wice.! the combined temperature is based on the equation:! the sum of the enthalpies of the two elements = that of the combined element.!!=======================================================================  USE PHYCON_MODULE ! physical constants  IMPLICIT NONE!-------------------------- Dummy argument -----------------------------!  real, INTENT(inout) :: &        dz,     &! nodal thickness of 1 elements being combined [m]        wliq,   &! liquid water of element 1        wice,   &! ice of element 1 [kg/m2]        t        ! nodel temperature of elment 1 [K]  real, INTENT(in) :: &        dz2,    &! nodal thickness of 2 elements being combined [m]        wliq2,  &! liquid water of element 2 [kg/m2]        wice2,  &! ice of element 2 [kg/m2]        t2       ! nodal temperature of element 2 [K]!!----------------------- Local variables ------------------------------!  real dzc,    &! Total thickness of nodes 1 and 2 (dzc=dz+dz2).       wliqc,  &! Combined liquid water [kg/m2]       wicec,  &! Combined ice [kg/m2]       tc,     &! Combined node temperature [K]       h,      &! enthalpy of element 1 [J/m2]       h2,     &! enthalpy of element 2 [J/m2]       hc       ! temporary!-----------------------------------------------------------------------      dzc = dz+dz2      wicec = (wice+wice2)      wliqc = (wliq+wliq2)      h   = (ci*wice+cl*wliq)*(t-tfrz)+dlm*wliq      h2  = (ci*wice2+cl*wliq2)*(t2-tfrz)+dlm*wliq2      hc = h + h2      if(hc < 0.)then         tc = tfrz + hc/(ci*wicec+cl*wliqc)      else if(hc.le.dlm*wliqc)then         tc = tfrz      else         tc = tfrz + (hc - dlm*wliqc)/(ci*wicec+cl*wliqc)      endif      dz = dzc      wice = wicec       wliq = wliqc      t = tc  END SUBROUTINE combo