var/da/da_radiance/siem_ats.inc

   1 subroutine siem_ats(theta,frequency,tba,ts,seaice_type,em_vector)
   2 !
   3 !$$$  subprogram documentation block
   4 !                .      .    .                                       .
   5 ! subprogram:
   6 !
   7 !   prgmmr: Banghua Yan                 org: nesdis              date: 2004-03-01
   8 !
   9 ! abstract:
  10 !         Calculate the emissivity discriminators and interpolate/extrapolate
  11 !  emissivity at required frequency with respect to secenery AMSUA & Ts
  12 !
  13 ! program history log:
  14 !   2004-10-28  treadon - correct out of bound problems for array coe
  15 !
  16 ! input argument list:
  17 !
  18 !      frequency        -  frequency in GHz
  19 !      theta            -  local zenith angle in radian
  20 !      ts               -  surface temperature
  21 !      tba[1] ~ tba[4]  -  brightness temperature at five AMSU-A window channels:
  22 !                              tba[1] : 23.8 GHz
  23 !                              tba[2] : 31.4 GHz
  24 !                              tba[3] : 50.3 GHz
  25 !                              tba[4] : 89   GHz
  26 !
  27 ! output argument list:
  28 !
  29 !   em_vector[1] and [2]  -  emissivity at two polarizations.
  30 !                              set esv = esh here and will be updated
  31 !       seaice_type        -     to be determined
  32 !
  33 ! important internal variables:
  34 !
  35 !   coe23   - fitting coefficients to estimate discriminator at 23.8 GHz
  36 !   coe31   - fitting coefficients to estimate discriminator at 31.4 GHz
  37 !   coe50   - fitting coefficients to estimate discriminator at 50.3 GHz
  38 !   coe89   - fitting coefficients to estimate discriminator at 89   GHz
  39 !
  40 ! remarks:
  41 !
  42 ! attributes:
  43 !   language: f90
  44 !   machine:  ibm rs/6000 sp
  45 !
  46 !$$$
  47
  48 !  use kinds, only: r_kind,i_kind
  49   implicit none
  50
  51   integer(i_kind),parameter:: nch =10,nwch = 5,ncoe = 4
  52   real(r_kind)    :: tba(*),theta
  53   real(r_kind)    :: em_vector(*),emissivity,ts,frequency,discriminator(nwch)
  54   integer(i_kind) :: seaice_type,i,k,ich,nvalid_ch
  55   real(r_kind)  :: coe23(0:ncoe),coe31(0:ncoe),coe50(0:ncoe),coe89(0:ncoe),coe150(0:ncoe)
  56   real(r_kind)  :: coe(nch*(ncoe+1))
  57
  58   Equivalence (coe(1),coe23)
  59   Equivalence (coe(11),coe31)
  60   Equivalence (coe(21),coe50)
  61   Equivalence (coe(31),coe89)
  62   Equivalence (coe(41),coe150)
  63
  64 ! Fitting Coefficients Using Tb1, Tb2, Tb4 and Ts
  65   data coe23/ 9.815214e-001_r_kind,  3.783815e-003_r_kind,  &
  66        6.391155e-004_r_kind, -9.106375e-005_r_kind, -4.263206e-003_r_kind/
  67   data coe31/ 9.047181e-001_r_kind, -2.782826e-004_r_kind,  &
  68        4.664207e-003_r_kind, -3.121744e-005_r_kind, -3.976189e-003_r_kind/
  69   data coe50/ 1.163853e+000_r_kind, -1.419205e-003_r_kind,  &
  70        5.505238e-003_r_kind,  1.506867e-003_r_kind, -6.157735e-003_r_kind/
  71   data coe89/  1.020753e+000_r_kind, -8.666064e-004_r_kind,  &
  72        9.624331e-004_r_kind,  4.878773e-003_r_kind, -5.055044e-003_r_kind/
  73   data coe150/ 1.438246e+000_r_kind,  5.667756e-004_r_kind, &
  74        -2.621972e-003_r_kind,  5.928146e-003_r_kind, -5.856687e-003_r_kind/
  75   save coe23,coe31,coe50,coe89,coe150
  76
  77
  78 ! Calculate emissivity discriminators at five AMSU window channels
  79
  80   do ich = 1, nwch
  81      discriminator(ich) = coe(1+(ich-1)*10)
  82      discriminator(ich) = discriminator(ich) + coe((ich-1)*10 + 2)*tba(1)  &
  83           + coe((ich-1)*10 + 3)*tba(2)  &
  84           + coe((ich-1)*10 + 4)*tba(4)  &
  85           + coe( (ich-1)*10 + 5 )*ts
  86   end do
  87
  88   call siem_interpolate(frequency,discriminator,emissivity,seaice_type)
  89
  90   em_vector(1) = emissivity
  91   em_vector(2) = emissivity
  92
  93
  94 end subroutine siem_ats