!     path:      $Source: /storm/rc1/cvsroot/rc/rrtmg_sw/src/rrtmg_sw_setcoef.f90,v $
!     author:    $Author: mike $
!     revision:  $Revision: 1.2 $
!     created:   $Date: 2007/08/23 20:40:14 $

      module rrtmg_sw_setcoef

!  --------------------------------------------------------------------------
! |                                                                          |
! |  Copyright 2002-2007, Atmospheric & Environmental Research, Inc. (AER).  |
! |  This software may be used, copied, or redistributed as long as it is    |
! |  not sold and this copyright notice is reproduced on each copy made.     |
! |  This model is provided as is without any express or implied warranties. |
! |                       (http://www.rtweb.aer.com/)                        |
! |                                                                          |
!  --------------------------------------------------------------------------

! ------- Modules -------

      use shr_kind_mod, only: r8 => shr_kind_r8

      use rrsw_ref,     only: pref, preflog, tref

      implicit none

      contains

!----------------------------------------------------------------------------
      subroutine setcoef_sw(nlayers, pavel, tavel, pz, tz, tbound, coldry, wkl, &
                            laytrop, layswtch, laylow, jp, jt, jt1, &
                            co2mult, colch4, colco2, colh2o, colmol, coln2o, &
                            colo2, colo3, fac00, fac01, fac10, fac11, &
                            selffac, selffrac, indself, forfac, forfrac, indfor)
!----------------------------------------------------------------------------
!
! Purpose:  For a given atmosphere, calculate the indices and
! fractions related to the pressure and temperature interpolations.

! Modifications:
! Original: J. Delamere, AER, Inc. (version 2.5, 02/04/01)
! Revised: Rewritten and adapted to ECMWF F90, JJMorcrette 030224
! Revised: For uniform rrtmg formatting, MJIacono, Jul 2006

! ------ Declarations -------

! ----- Input -----
      integer, intent(in) :: nlayers         ! total number of layers

      real(kind=r8), intent(in) :: pavel(:)           ! layer pressures (mb) 
                                                        !    Dimensions: (nlayers)
      real(kind=r8), intent(in) :: tavel(:)           ! layer temperatures (K)
                                                        !    Dimensions: (nlayers)
      real(kind=r8), intent(in) :: pz(0:)             ! level (interface) pressures (hPa, mb)
                                                        !    Dimensions: (0:nlayers)
      real(kind=r8), intent(in) :: tz(0:)             ! level (interface) temperatures (K)
                                                        !    Dimensions: (0:nlayers)
      real(kind=r8), intent(in) :: tbound             ! surface temperature (K)
      real(kind=r8), intent(in) :: coldry(:)          ! dry air column density (mol/cm2)
                                                        !    Dimensions: (nlayers)
      real(kind=r8), intent(in) :: wkl(:,:)           ! molecular amounts (mol/cm-2)
                                                        !    Dimensions: (mxmol,nlayers)

! ----- Output -----
      integer, intent(out) :: laytrop        ! tropopause layer index
      integer, intent(out) :: layswtch       ! 
      integer, intent(out) :: laylow         ! 

      integer, intent(out) :: jp(:)          ! 
                                                        !    Dimensions: (nlayers)
      integer, intent(out) :: jt(:)          !
                                                        !    Dimensions: (nlayers)
      integer, intent(out) :: jt1(:)         !
                                                        !    Dimensions: (nlayers)

      real(kind=r8), intent(out) :: colh2o(:)         ! column amount (h2o)
                                                        !    Dimensions: (nlayers)
      real(kind=r8), intent(out) :: colco2(:)         ! column amount (co2)
                                                        !    Dimensions: (nlayers)
      real(kind=r8), intent(out) :: colo3(:)          ! column amount (o3)
                                                        !    Dimensions: (nlayers)
      real(kind=r8), intent(out) :: coln2o(:)         ! column amount (n2o)
                                                        !    Dimensions: (nlayers)
      real(kind=r8), intent(out) :: colch4(:)         ! column amount (ch4)
                                                        !    Dimensions: (nlayers)
      real(kind=r8), intent(out) :: colo2(:)          ! column amount (o2)
                                                        !    Dimensions: (nlayers)
      real(kind=r8), intent(out) :: colmol(:)         ! 
                                                        !    Dimensions: (nlayers)
      real(kind=r8), intent(out) :: co2mult(:)        !
                                                        !    Dimensions: (nlayers)

      integer, intent(out) :: indself(:)
                                                        !    Dimensions: (nlayers)
      integer, intent(out) :: indfor(:)
                                                        !    Dimensions: (nlayers)
      real(kind=r8), intent(out) :: selffac(:)
                                                        !    Dimensions: (nlayers)
      real(kind=r8), intent(out) :: selffrac(:)
                                                        !    Dimensions: (nlayers)
      real(kind=r8), intent(out) :: forfac(:)
                                                        !    Dimensions: (nlayers)
      real(kind=r8), intent(out) :: forfrac(:)
                                                        !    Dimensions: (nlayers)

      real(kind=r8), intent(out) :: &                 !
                         fac00(:), fac01(:), &          !    Dimensions: (nlayers)
                         fac10(:), fac11(:) 

! ----- Local -----

      integer :: indbound
      integer :: indlev0
      integer :: lay
      integer :: jp1

      real(kind=r8) :: stpfac
      real(kind=r8) :: tbndfrac
      real(kind=r8) :: t0frac
      real(kind=r8) :: plog
      real(kind=r8) :: fp
      real(kind=r8) :: ft
      real(kind=r8) :: ft1
      real(kind=r8) :: water
      real(kind=r8) :: scalefac
      real(kind=r8) :: factor
      real(kind=r8) :: co2reg
      real(kind=r8) :: compfp


! Initializations
      stpfac = 296._r8/1013._r8

      indbound = tbound - 159._r8
      tbndfrac = tbound - int(tbound)
      indlev0  = tz(0) - 159._r8
      t0frac   = tz(0) - int(tz(0))

      laytrop  = 0
      layswtch = 0
      laylow   = 0

! Begin layer loop
      do lay = 1, nlayers
! Find the two reference pressures on either side of the
! layer pressure.  Store them in JP and JP1.  Store in FP the
! fraction of the difference (in ln(pressure)) between these
! two values that the layer pressure lies.

         plog = log(pavel(lay))
         jp(lay) = int(36._r8 - 5*(plog+0.04_r8))
         if (jp(lay) .lt. 1) then
            jp(lay) = 1
         elseif (jp(lay) .gt. 58) then
            jp(lay) = 58
         endif
         jp1 = jp(lay) + 1
         fp = min(3._r8, max(-2._r8, 5._r8 * (preflog(jp(lay)) - plog)))

! Determine, for each reference pressure (JP and JP1), which
! reference temperature (these are different for each  
! reference pressure) is nearest the layer temperature but does
! not exceed it.  Store these indices in JT and JT1, resp.
! Store in FT (resp. FT1) the fraction of the way between JT
! (JT1) and the next highest reference temperature that the 
! layer temperature falls.

         jt(lay) = int(3._r8 + (tavel(lay)-tref(jp(lay)))/15._r8)
         if (jt(lay) .lt. 1) then
            jt(lay) = 1
         elseif (jt(lay) .gt. 4) then
            jt(lay) = 4
         endif
         ft = min(3._r8, max(-2._r8, ((tavel(lay)-tref(jp(lay)))/15._r8) - float(jt(lay)-3)))
         jt1(lay) = int(3._r8 + (tavel(lay)-tref(jp1))/15._r8)
         if (jt1(lay) .lt. 1) then
            jt1(lay) = 1
         elseif (jt1(lay) .gt. 4) then
            jt1(lay) = 4
         endif
         ft1 = min(3._r8, max(-2._r8, ((tavel(lay)-tref(jp1))/15._r8) - float(jt1(lay)-3)))

         water = wkl(1,lay)/coldry(lay)
         scalefac = pavel(lay) * stpfac / tavel(lay)

! If the pressure is less than ~100mb, perform a different
! set of species interpolations.

         if (plog .le. 4.56_r8) go to 5300
         laytrop =  laytrop + 1
         if (plog .ge. 6.62_r8) laylow = laylow + 1

! Set up factors needed to separately include the water vapor
! foreign-continuum in the calculation of absorption coefficient.

         forfac(lay) = scalefac / (1.+water)
         factor = (332.0_r8-tavel(lay))/36.0_r8
         indfor(lay) = min(2, max(1, int(factor)))
         forfrac(lay) = min(3._r8, max(-2._r8, factor - float(indfor(lay))))

! Set up factors needed to separately include the water vapor
! self-continuum in the calculation of absorption coefficient.

         selffac(lay) = water * forfac(lay)
         factor = (tavel(lay)-188.0_r8)/7.2_r8
         indself(lay) = min(9, max(1, int(factor)-7))
         selffrac(lay) = min(3._r8, max(-2._r8, factor - float(indself(lay) + 7)))

! Calculate needed column amounts.

         colh2o(lay) = 1.e-20_r8 * wkl(1,lay)
         colco2(lay) = 1.e-20_r8 * wkl(2,lay)
         colo3(lay) = 1.e-20_r8 * wkl(3,lay)
!           colo3(lay) = 0._r8
!           colo3(lay) = colo3(lay)/1.16_r8
         coln2o(lay) = 1.e-20_r8 * wkl(4,lay)
         colch4(lay) = 1.e-20_r8 * wkl(6,lay)
         colo2(lay) = 1.e-20_r8 * wkl(7,lay)
         colmol(lay) = 1.e-20_r8 * coldry(lay) + colh2o(lay)
!           colco2(lay) = 0._r8
!           colo3(lay) = 0._r8
!           coln2o(lay) = 0._r8
!           colch4(lay) = 0._r8
!           colo2(lay) = 0._r8
!           colmol(lay) = 0._r8
         if (colco2(lay) .eq. 0._r8) colco2(lay) = 1.e-32_r8 * coldry(lay)
         if (coln2o(lay) .eq. 0._r8) coln2o(lay) = 1.e-32_r8 * coldry(lay)
         if (colch4(lay) .eq. 0._r8) colch4(lay) = 1.e-32_r8 * coldry(lay)
         if (colo2(lay) .eq. 0._r8) colo2(lay) = 1.e-32_r8 * coldry(lay)
! Using E = 1334.2 cm-1.
         co2reg = 3.55e-24_r8 * coldry(lay)
         co2mult(lay)= (colco2(lay) - co2reg) * &
               272.63_r8*exp(-1919.4_r8/tavel(lay))/(8.7604e-4_r8*tavel(lay))
         goto 5400

! Above laytrop.
 5300    continue

! Set up factors needed to separately include the water vapor
! foreign-continuum in the calculation of absorption coefficient.

         forfac(lay) = scalefac / (1.+water)
         factor = (tavel(lay)-188.0_r8)/36.0_r8
         indfor(lay) = 3
         forfrac(lay) = min(3._r8, max(-2._r8, factor - 1.0_r8))

! Calculate needed column amounts.

         colh2o(lay) = 1.e-20_r8 * wkl(1,lay)
         colco2(lay) = 1.e-20_r8 * wkl(2,lay)
         colo3(lay)  = 1.e-20_r8 * wkl(3,lay)
         coln2o(lay) = 1.e-20_r8 * wkl(4,lay)
         colch4(lay) = 1.e-20_r8 * wkl(6,lay)
         colo2(lay)  = 1.e-20_r8 * wkl(7,lay)
         colmol(lay) = 1.e-20_r8 * coldry(lay) + colh2o(lay)
         if (colco2(lay) .eq. 0._r8) colco2(lay) = 1.e-32_r8 * coldry(lay)
         if (coln2o(lay) .eq. 0._r8) coln2o(lay) = 1.e-32_r8 * coldry(lay)
         if (colch4(lay) .eq. 0._r8) colch4(lay) = 1.e-32_r8 * coldry(lay)
         if (colo2(lay)  .eq. 0._r8) colo2(lay)  = 1.e-32_r8 * coldry(lay)
         co2reg = 3.55e-24_r8 * coldry(lay)
         co2mult(lay)= (colco2(lay) - co2reg) * &
               272.63_r8*exp(-1919.4_r8/tavel(lay))/(8.7604e-4_r8*tavel(lay))

         selffac(lay) = 0._r8
         selffrac(lay)= 0._r8
         indself(lay) = 0

 5400    continue

! We have now isolated the layer ln pressure and temperature,
! between two reference pressures and two reference temperatures 
! (for each reference pressure).  We multiply the pressure 
! fraction FP with the appropriate temperature fractions to get 
! the factors that will be needed for the interpolation that yields
! the optical depths (performed in routines TAUGBn for band n).

         compfp = 1._r8 - fp
         fac10(lay) = compfp * ft
         fac00(lay) = compfp * (1._r8 - ft)
         fac11(lay) = fp * ft1
         fac01(lay) = fp * (1._r8 - ft1)

! End layer loop
      enddo

      end subroutine setcoef_sw

!***************************************************************************
      subroutine swatmref
!***************************************************************************

      save
 
! These pressures are chosen such that the ln of the first pressure
! has only a few non-zero digits (i.e. ln(PREF(1)) = 6.96000) and
! each subsequent ln(pressure) differs from the previous one by 0.2.

      pref(:) = (/ &
          1.05363e+03_r8,8.62642e+02_r8,7.06272e+02_r8,5.78246e+02_r8,4.73428e+02_r8, &
          3.87610e+02_r8,3.17348e+02_r8,2.59823e+02_r8,2.12725e+02_r8,1.74164e+02_r8, &
          1.42594e+02_r8,1.16746e+02_r8,9.55835e+01_r8,7.82571e+01_r8,6.40715e+01_r8, &
          5.24573e+01_r8,4.29484e+01_r8,3.51632e+01_r8,2.87892e+01_r8,2.35706e+01_r8, &
          1.92980e+01_r8,1.57998e+01_r8,1.29358e+01_r8,1.05910e+01_r8,8.67114e+00_r8, &
          7.09933e+00_r8,5.81244e+00_r8,4.75882e+00_r8,3.89619e+00_r8,3.18993e+00_r8, &
          2.61170e+00_r8,2.13828e+00_r8,1.75067e+00_r8,1.43333e+00_r8,1.17351e+00_r8, &
          9.60789e-01_r8,7.86628e-01_r8,6.44036e-01_r8,5.27292e-01_r8,4.31710e-01_r8, &
          3.53455e-01_r8,2.89384e-01_r8,2.36928e-01_r8,1.93980e-01_r8,1.58817e-01_r8, &
          1.30029e-01_r8,1.06458e-01_r8,8.71608e-02_r8,7.13612e-02_r8,5.84256e-02_r8, &
          4.78349e-02_r8,3.91639e-02_r8,3.20647e-02_r8,2.62523e-02_r8,2.14936e-02_r8, &
          1.75975e-02_r8,1.44076e-02_r8,1.17959e-02_r8,9.65769e-03_r8 /)

      preflog(:) = (/ &
           6.9600e+00_r8, 6.7600e+00_r8, 6.5600e+00_r8, 6.3600e+00_r8, 6.1600e+00_r8, &
           5.9600e+00_r8, 5.7600e+00_r8, 5.5600e+00_r8, 5.3600e+00_r8, 5.1600e+00_r8, &
           4.9600e+00_r8, 4.7600e+00_r8, 4.5600e+00_r8, 4.3600e+00_r8, 4.1600e+00_r8, &
           3.9600e+00_r8, 3.7600e+00_r8, 3.5600e+00_r8, 3.3600e+00_r8, 3.1600e+00_r8, &
           2.9600e+00_r8, 2.7600e+00_r8, 2.5600e+00_r8, 2.3600e+00_r8, 2.1600e+00_r8, &
           1.9600e+00_r8, 1.7600e+00_r8, 1.5600e+00_r8, 1.3600e+00_r8, 1.1600e+00_r8, &
           9.6000e-01_r8, 7.6000e-01_r8, 5.6000e-01_r8, 3.6000e-01_r8, 1.6000e-01_r8, &
          -4.0000e-02_r8,-2.4000e-01_r8,-4.4000e-01_r8,-6.4000e-01_r8,-8.4000e-01_r8, &
          -1.0400e+00_r8,-1.2400e+00_r8,-1.4400e+00_r8,-1.6400e+00_r8,-1.8400e+00_r8, &
          -2.0400e+00_r8,-2.2400e+00_r8,-2.4400e+00_r8,-2.6400e+00_r8,-2.8400e+00_r8, &
          -3.0400e+00_r8,-3.2400e+00_r8,-3.4400e+00_r8,-3.6400e+00_r8,-3.8400e+00_r8, &
          -4.0400e+00_r8,-4.2400e+00_r8,-4.4400e+00_r8,-4.6400e+00_r8 /)

! These are the temperatures associated with the respective 
! pressures for the MLS standard atmosphere. 

      tref(:) = (/ &
           2.9420e+02_r8, 2.8799e+02_r8, 2.7894e+02_r8, 2.6925e+02_r8, 2.5983e+02_r8, &
           2.5017e+02_r8, 2.4077e+02_r8, 2.3179e+02_r8, 2.2306e+02_r8, 2.1578e+02_r8, &
           2.1570e+02_r8, 2.1570e+02_r8, 2.1570e+02_r8, 2.1706e+02_r8, 2.1858e+02_r8, &
           2.2018e+02_r8, 2.2174e+02_r8, 2.2328e+02_r8, 2.2479e+02_r8, 2.2655e+02_r8, &
           2.2834e+02_r8, 2.3113e+02_r8, 2.3401e+02_r8, 2.3703e+02_r8, 2.4022e+02_r8, &
           2.4371e+02_r8, 2.4726e+02_r8, 2.5085e+02_r8, 2.5457e+02_r8, 2.5832e+02_r8, &
           2.6216e+02_r8, 2.6606e+02_r8, 2.6999e+02_r8, 2.7340e+02_r8, 2.7536e+02_r8, &
           2.7568e+02_r8, 2.7372e+02_r8, 2.7163e+02_r8, 2.6955e+02_r8, 2.6593e+02_r8, &
           2.6211e+02_r8, 2.5828e+02_r8, 2.5360e+02_r8, 2.4854e+02_r8, 2.4348e+02_r8, & 
           2.3809e+02_r8, 2.3206e+02_r8, 2.2603e+02_r8, 2.2000e+02_r8, 2.1435e+02_r8, &
           2.0887e+02_r8, 2.0340e+02_r8, 1.9792e+02_r8, 1.9290e+02_r8, 1.8809e+02_r8, &
           1.8329e+02_r8, 1.7849e+02_r8, 1.7394e+02_r8, 1.7212e+02_r8 /)

      end subroutine swatmref

      end module rrtmg_sw_setcoef


