SUBROUTINE OPTCV(DTAUV,TAUV,TAUCUMV,PLEV,  &
          QXVAER,QSVAER,GVAER,WBARV,COSBV,       &
          TAURAY,TAUAERO,TMID,PMID,TAUGSURF,QVAR,MUVAR)

      use radinc_h
      use radcommon_h, only: gasv, tlimit, wrefVAR, Cmk, tgasref, pfgasref,wnov,scalep
      use gases_h

      implicit none

!==================================================================
!     
!     Purpose
!     -------
!     Calculates shortwave optical constants at each level.
!     
!     Authors
!     -------
!     Adapted from the NASA Ames code by R. Wordsworth (2009)
!     
!==================================================================
!     
!     THIS SUBROUTINE SETS THE OPTICAL CONSTANTS IN THE VISUAL  
!     IT CALCUALTES FOR EACH LAYER, FOR EACH SPECRAL INTERVAL IN THE VISUAL
!     LAYER: WBAR, DTAU, COSBAR
!     LEVEL: TAU
!     
!     TAUV(L,NW,NG) is the cumulative optical depth at the top of radiation code
!     layer L. NW is spectral wavelength interval, ng the Gauss point index.
!     
!     TLEV(L) - Temperature at the layer boundary
!     PLEV(L) - Pressure at the layer boundary (i.e. level)
!     GASV(NT,NPS,NW,NG) - Visible k-coefficients 
!     
!-------------------------------------------------------------------

#include "callkeys.h"
#include "comcstfi.h"

      real*8 DTAUV(L_NLAYRAD,L_NSPECTV,L_NGAUSS)
      real*8 DTAUKV(L_LEVELS+1,L_NSPECTV,L_NGAUSS)
      real*8 TAUV(L_NLEVRAD,L_NSPECTV,L_NGAUSS)
      real*8 TAUCUMV(L_LEVELS,L_NSPECTV,L_NGAUSS)
      real*8 PLEV(L_LEVELS)
      real*8 TMID(L_LEVELS), PMID(L_LEVELS)
      real*8 COSBV(L_NLAYRAD,L_NSPECTV,L_NGAUSS)
      real*8 WBARV(L_NLAYRAD,L_NSPECTV,L_NGAUSS)
      real*8 TAURAY(L_NSPECTV)

!     For aerosols
      real*8 QXVAER(L_LEVELS+1,L_NSPECTV,NAERKIND)
      real*8 QSVAER(L_LEVELS+1,L_NSPECTV,NAERKIND)
      real*8 GVAER(L_LEVELS+1,L_NSPECTV,NAERKIND)
      real*8 TAUAERO(L_LEVELS+1,NAERKIND)
      real*8 TAUAEROLK(L_LEVELS+1,L_NSPECTV,NAERKIND)
      real*8 TAEROS(L_LEVELS,L_NSPECTV,NAERKIND)

      integer L, NW, NG, K, NG1(L_NSPECTV), LK, IAER
      integer MT(L_LEVELS), MP(L_LEVELS), NP(L_LEVELS)
      real*8  ANS, TAUGAS
      real*8  TRAY(L_LEVELS,L_NSPECTV)
      real*8  DPR(L_LEVELS), U(L_LEVELS)
      real*8  LCOEF(4), LKCOEF(L_LEVELS,4)

      real*8 taugsurf(L_NSPECTV,L_NGAUSS-1), TRAYAER

!     Variable species mixing ratio variables
      real*8 QVAR(L_LEVELS), WRATIO(L_LEVELS), MUVAR(L_LEVELS)
      real*8 KCOEF(4)
      integer NVAR(L_LEVELS)

!     temporary variables for multiple aerosol calculation
      real*8 atemp, btemp, ctemp

!     variables for k in units m^-1
      double precision wn_cont, p_cont, p_air, T_cont, dtemp
      real*8 dz(L_LEVELS), DCONT

      integer igas

!=======================================================================
!     Determine the total gas opacity throughout the column, for each
!     spectral interval, NW, and each Gauss point, NG.
!     Calculate the continuum opacities, i.e., those that do not depend on
!     NG, the Gauss index.

      taugsurf(:,:) = 0.0
      dpr(:)        = 0.0
      lkcoef(:,:)   = 0.0

      do K=2,L_LEVELS
         DPR(k) = PLEV(K)-PLEV(K-1)

         ! if we have continuum opacities, we need dz
         if(kastprof)then
            dz(k) = dpr(k)*(8314.5/muvar(k))*TMID(K)/(g*PMID(K))
            U(k)  = (Cmk*mugaz/(muvar(k)))*DPR(k) 
         else
            dz(k) = dpr(k)*R*TMID(K)/(g*PMID(K))
            U(k)  = Cmk*DPR(k)    ! only Cmk line in optci.F
         endif

         call tpindex(PMID(K),TMID(K),QVAR(K),pfgasref,tgasref,WREFVAR, &
              LCOEF,MT(K),MP(K),NVAR(K),WRATIO(K))

         do LK=1,4
            LKCOEF(K,LK) = LCOEF(LK)
         end do

         DO NW=1,L_NSPECTV
            TRAY(K,NW)   = TAURAY(NW) * DPR(K)

            do iaer=1,naerkind
               TAEROS(K,NW,IAER) = TAUAERO(K,IAER)  * QXVAER(K,NW,IAER)
            end do
!     

         END DO
      end do

!     TRAYAER is Tau RAYleigh scattering, plus AERosol opacity

!     we ignore K=1...
      do K=2,L_LEVELS
         do NW=1,L_NSPECTV

            TRAYAER = TRAY(K,NW)
            do iaer=1,naerkind
               TRAYAER = TRAYAER + TAEROS(K,NW,IAER)
            end do

            DCONT = 0.0 ! continuum absorption

            ! include continua if necessary
            wn_cont = dble(wnov(nw))
            T_cont  = dble(TMID(k))
            do igas=1,ngasmx

               if(gfrac(igas).eq.-1)then ! variable
                  p_cont  = dble(PMID(k)*scalep*QVAR(K)) ! qvar = mol/mol
               else
                  p_cont  = dble(PMID(k)*scalep*gfrac(igas)*(1.-QVAR(k)))
               endif

               dtemp=0.0
               if(gnom(igas).eq.'H2_')then 
                  call interpolateH2H2(wn_cont,T_cont,p_cont,dtemp,.false.)
               elseif(gnom(igas).eq.'H2O'.and.T_cont.gt.200.0)then
                  p_air = dble(PMID(k)*scalep) - p_cont ! note assumes air!!
                  call interpolateH2Ocont(wn_cont,T_cont,p_cont,p_air,dtemp,.false.)
               endif

               DCONT = DCONT + dtemp

            enddo

            DCONT = DCONT*dz(k) 

            if(.not.(callgasvis.and.Continuum))then
               DCONT=0.0
            endif

            do NG=1,L_NGAUSS-1

!=======================================================================
!     Now compute TAUGAS
!     Interpolate between water mixing ratios
!     WRATIO = 0.0 if the requested water amount is equal to, or outside the
!     the water data range

               if (L_REFVAR.eq.1)then ! added by RW for special no variable case
                  KCOEF(1) = GASV(MT(K),MP(K),1,NW,NG)
                  KCOEF(2) = GASV(MT(K),MP(K)+1,1,NW,NG)
                  KCOEF(3) = GASV(MT(K)+1,MP(K)+1,1,NW,NG)
                  KCOEF(4) = GASV(MT(K)+1,MP(K),1,NW,NG)
               else
                  KCOEF(1) = GASV(MT(K),MP(K),NVAR(K),NW,NG) + WRATIO(K)*    &
                       (GASV(MT(K),MP(K),NVAR(K)+1,NW,NG) -                  &
                       GASV(MT(K),MP(K),NVAR(K),NW,NG))

                  KCOEF(2) = GASV(MT(K),MP(K)+1,NVAR(K),NW,NG) + WRATIO(K)*  &
                       (GASV(MT(K),MP(K)+1,NVAR(K)+1,NW,NG) -                &
                       GASV(MT(K),MP(K)+1,NVAR(K),NW,NG))

                  KCOEF(3) = GASV(MT(K)+1,MP(K)+1,NVAR(K),NW,NG) + WRATIO(K)*&
                       (GASV(MT(K)+1,MP(K)+1,NVAR(K)+1,NW,NG) -              &
                       GASV(MT(K)+1,MP(K)+1,NVAR(K),NW,NG))

                  KCOEF(4) = GASV(MT(K)+1,MP(K),NVAR(K),NW,NG) + WRATIO(K)*  &
                       (GASV(MT(K)+1,MP(K),NVAR(K)+1,NW,NG) -                &
                       GASV(MT(K)+1,MP(K),NVAR(K),NW,NG))
               endif

!     Interpolate the gaseous k-coefficients to the requested T,P values
               
               ANS = LKCOEF(K,1)*KCOEF(1) + LKCOEF(K,2)*KCOEF(2) +           &
                    LKCOEF(K,3)*KCOEF(3) + LKCOEF(K,4)*KCOEF(4)

               TAUGAS          = U(k)*ANS

               if(graybody)then
                  TAUGAS = 0.0
                  DCONT  = 0.0
               endif



               !TAUGSURF(NW,NG) = TAUGSURF(NW,NG) + TAUGAS
               TAUGSURF(NW,NG) = TAUGSURF(NW,NG) + TAUGAS + DCONT
               DTAUKV(K,nw,ng) = TAUGAS + TRAYAER  & ! TRAYAER includes all scattering contributions
                                 + DCONT             ! for continuum absorption

            end do


!     Now fill in the "clear" part of the spectrum (NG = L_NGAUSS),
!     which holds continuum opacity only

            NG = L_NGAUSS
            DTAUKV(K,nw,ng) = TRAY(K,NW) + DCONT ! For parameterized continuum absorption
            do iaer=1,naerkind
               DTAUKV(K,nw,ng) = DTAUKV(K,nw,ng) + TAEROS(K,NW,IAER)
!     &                           + DCONT          ! For parameterized continuum absorption
            end do ! a bug was here!

         end do
      end do


!=======================================================================
!     Now the full treatment for the layers, where besides the opacity
!     we need to calculate the scattering albedo and asymmetry factors

      DO NW=1,L_NSPECTV
         DO K=2,L_LEVELS
            do iaer=1,naerkind
              TAUAEROLK(K,NW,IAER) = TAUAERO(K,IAER) * QSVAER(K,NW,IAER)
            end do
         ENDDO
      ENDDO
      

      DO NW=1,L_NSPECTV
         DO NG=1,L_NGAUSS
            DO L=1,L_NLAYRAD-1
               K              = 2*L+1

               DTAUV(L,nw,ng) = DTAUKV(K,NW,NG)+DTAUKV(K+1,NW,NG)

               atemp=0.
               btemp=TRAY(K,NW) + TRAY(K+1,NW)
               ctemp=0.9999*(TRAY(K,NW) + TRAY(K+1,NW))
               do iaer=1,naerkind
                  atemp = atemp +                                     &
                       GVAER(K,NW,IAER)   * TAUAEROLK(K,NW,IAER) +    &
                       GVAER(K+1,NW,IAER) * TAUAEROLK(K+1,NW,IAER)
                  btemp = btemp +                                     &
                       TAUAEROLK(K,NW,IAER) + TAUAEROLK(K+1,NW,IAER)
                  ctemp = ctemp +                                     &
                       TAUAEROLK(K,NW,IAER) + TAUAEROLK(K+1,NW,IAER)
               end do

               COSBV(L,NW,NG) = atemp/btemp
               WBARV(L,nw,ng) = ctemp/DTAUV(L,nw,ng)

            END DO

!     No vertical averaging on bottom layer

            L              = L_NLAYRAD
            K              = 2*L+1
            DTAUV(L,nw,ng) = DTAUKV(K,NW,NG)

            atemp=0.
            btemp=TRAY(K,NW)
            ctemp=0.9999*TRAY(K,NW)
            do iaer=1,naerkind
               atemp = atemp + GVAER(K,NW,IAER) * TAUAEROLK(K,NW,IAER) 
               btemp = btemp + TAUAEROLK(K,NW,IAER) 
               ctemp = ctemp + TAUAEROLK(K,NW,IAER)
            end do
            COSBV(L,NW,NG) = atemp/btemp
            WBARV(L,nw,ng) = ctemp/DTAUV(L,nw,ng)

         END DO                 ! NG gauss point loop
      END DO                    ! NW spectral loop



!     Total extinction optical depths

      DO NW=1,L_NSPECTV        
         DO NG=1,L_NGAUSS       ! full gauss loop
            TAUV(1,NW,NG)=0.0D0
            DO L=1,L_NLAYRAD
               TAUV(L+1,NW,NG)=TAUV(L,NW,NG)+DTAUV(L,NW,NG)
            END DO

            TAUCUMV(1,NW,NG)=0.0D0
            DO K=2,L_LEVELS
               TAUCUMV(K,NW,NG)=TAUCUMV(K-1,NW,NG)+DTAUKV(K,NW,NG)
            END DO
         END DO                 ! end full gauss loop
      END DO


      RETURN
    END SUBROUTINE OPTCV