QSAT

INTERFACE:

   subroutine QSat (T, p, es, esdT, qs, qsdT)

DESCRIPTION:

   Computes saturation mixing ratio and the change in saturation
   mixing ratio with respect to temperature.
   Reference:  Polynomial approximations from:
               Piotr J. Flatau, et al.,1992:  Polynomial fits to saturation 
               vapor pressure.  Journal of Applied Meteorology, 31, 1507-1513.

USES:

     use shr_kind_mod, only: r8 => shr_kind_r8
     use shr_const_mod, ONLY: SHR_CONST_TKFRZ

ARGUMENTS:

     implicit none
     real(r8), intent(in)  :: T        ! temperature (K)
     real(r8), intent(in)  :: p        ! surface atmospheric pressure (pa)
     real(r8), intent(out) :: es       ! vapor pressure (pa)
     real(r8), intent(out) :: esdT     ! d(es)/d(T)
     real(r8), intent(out) :: qs       ! humidity (kg/kg)
     real(r8), intent(out) :: qsdT     ! d(qs)/d(T)

CALLED FROM:

   subroutine Biogeophysics1 in module Biogeophysics1Mod
   subroutine BiogeophysicsLake in module BiogeophysicsLakeMod
   subroutine CanopyFluxesMod CanopyFluxesMod

REVISION HISTORY:

   15 September 1999: Yongjiu Dai; Initial code
   15 December 1999:  Paul Houser and Jon Radakovich; F90 Revision