da_tprh_to_q_lin.inc

1 subroutine da_tprh_to_q_lin( xb, xp, xa )
2 
3    !---------------------------------------------------------------------------
4    ! Purpose: Convert T/pressure/rh to specific humidity increments.
5    !
6    ! Method: q~ = q (rh~/rh + qs~/qs)
7    !---------------------------------------------------------------------------
8 
9    implicit none
10    
11    type (xb_type), intent(in)    :: xb           ! First guess structure.
12    type (xpose_type), intent(in) :: xp           ! Dimensions and xpose buffers.
13    type (x_type), intent(inout)  :: xa           ! increment structure.
14    
15    integer                       :: is, ie       ! 1st dim. end points.
16    integer                       :: js, je       ! 2nd dim. end points.
17    integer                       :: ks, ke       ! 3rd dim. end points.
18    real :: qs_prime_over_qs(xp%its:xp%ite,xp%jts:xp%jte,xp%kts:xp%kte) ! qs~/qs.
19 
20    !---------------------------------------------------------------------------
21    !  [1.0] initialise:
22    !---------------------------------------------------------------------------
23 
24    is = xp%its; ie = xp%ite
25    js = xp%jts; je = xp%jte
26    ks = xp%kts; ke = xp%kte   
27 
28    !---------------------------------------------------------------------------
29    ! [1.0] Calculate saturation specific humidity ratio qs~/qs:
30    !---------------------------------------------------------------------------
31 
32    call da_tp_to_qs_lin( xb, xp, xa, qs_prime_over_qs )
33    
34    !---------------------------------------------------------------------------
35    ! [2.0] Calculate specific humidity increment:
36    !---------------------------------------------------------------------------
37 
38    xa % q(is:ie,js:je,ks:ke) = xb % q(is:ie,js:je,ks:ke) * &
39                                ( xa % rh(is:ie,js:je,ks:ke) / &
40                                  xb % rh(is:ie,js:je,ks:ke) + &
41                                  qs_prime_over_qs(is:ie,js:je,ks:ke) )
42 
43 end subroutine da_tprh_to_q_lin
44 
45