ehv2pem.inc

1 subroutine ehv2pem( ehorz0,evert0,zlsat0,polar0, pems0)
2 !$$$   module documentation block
3 !                .      .    .                                       .
4 ! module: ehv2pem  combine V and H.pol emissivity
5 !   prgmmr: okamoto          org: np23                date: 2004-08-06
6 !
7 ! abstract:  combine vertical and horizontal polarized emissivity.
8 !            effective for cross-track scan type sensor such as AMSU
9 !            In contrast, for ssm/i, pems(V)=evert0, pems(H)=ehorz0,
10 !            as they are
11 !
12 ! program history log:
13 !   2004-08-06  okamoto
14 !
15 !   input argument list:
16 !     zlsat0 - satellite look angle in radians
17 !     polar  - channel polarization (0=vertical, 1=horizontal, or
18 !                                      0 to 1=mix of V and H)
19 !     ehorz0 - emissivity at horizontal polarization
20 !     evert0 - emissivity at vertical polarization
21 !
22 !   output argument list:
23 !     pems0  - surface emissivity at obs location
24 !
25 ! attributes:
26 !   language: cft77
27 !   machine:  IBM sp
28 !
29 !$$$
30     implicit none
31     real(r_kind):: ehorz0,evert0,zlsat0,polar0, pems0
32     real(r_kind):: pcl2,psl2,term1,term2
33     pcl2=cos(zlsat0)**2
34     psl2=sin(zlsat0)**2
35     term1 = evert0*pcl2 + ehorz0*psl2
36     term2 = evert0*psl2 + ehorz0*pcl2
37     pems0 = (one-polar0)*term1 + polar0*term2
38     return
39   end subroutine ehv2pem