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subroutine da_tp_to_qs1 (grid, es, qs) 1,2
!---------------------------------------------------------------------------
! Purpose: Convert T/p to saturation specific humidity.
!
! Method: qs = es_alpha * es / ( p - ( 1 - rd_over_rv ) * es ).
! use Rogers & Yau (1989) formula: es = a exp( bTc / (T_c + c) ).
!
! This da_tp_to_qs1 was added and called by the corrected subroutine
! da_tpq_to_rh_lin.
!---------------------------------------------------------------------------
implicit none
type (domain), intent(in) :: grid
real, intent(out) :: es(its:ite,jts:jte,kts:kte)
real, intent(out) :: qs(its:ite,jts:jte,kts:kte)
integer :: i, j, k ! Loop counters.
real :: t_c ! Working variable.
if (trace_use_dull) call da_trace_entry
("da_tp_to_qs1")
!---------------------------------------------------------------------------
! [1.0] initialise:
!---------------------------------------------------------------------------
do k = kts, kte
do j = jts, jte
do i = its, ite
!------------------------------------------------------------------
! [1.0] initialise:
!------------------------------------------------------------------
t_c = grid%xb % t(i,j,k) - t_kelvin
!------------------------------------------------------------------
! [2.0] Calculate saturation vapour pressure:
!------------------------------------------------------------------
es(i,j,k) = es_alpha * exp( es_beta * t_c / ( t_c + es_gamma ) )
!------------------------------------------------------------------
! [3.0] Calculate saturation specific humidity:
!------------------------------------------------------------------
qs(i,j,k) = rd_over_rv * es(i,j,k) / &
(grid%xb % p(i,j,k) - rd_over_rv1 * es(i,j,k))
end do
end do
end do
if (trace_use_dull) call da_trace_exit("da_tp_to_qs1")
end subroutine da_tp_to_qs1