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subroutine da_predictor_rttov(inst, pred,npred,nlevels,temp,hum,t_skin) 3,2
implicit none
! temp - RTM level temperatures (k)
! hum - RTM level moistures (kg/kg)
! t-skin - model skin temperature (k)
! nlevels - number of RTM levels (1:nlevels)
! pf - RTM full level pressure (hpa)
! pred(1) - 1000-300 thickness
! pred(2) - 200-50 thickness
! pred(3) - t_skin
! pred(4) - total column precipitable water
integer, intent(in) :: inst, npred, nlevels
real, intent(in) :: temp(nlevels), hum(nlevels), t_skin
real, intent(out) :: pred(npred)
real, parameter :: kth = gas_constant/gravity
real, parameter :: kpc = 100.0/gravity
real :: pf(nlevels)
real :: tv(nlevels-1), qm(nlevels-1)
real :: dlp(nlevels-1), dp(nlevels-1)
real :: add_thk
integer :: itmp(1), k
integer :: index1000, index300, index200, index50
if (trace_use) call da_trace_entry
("da_predictor_rttov")
pf = coefs(inst)%coef%ref_prfl_p
do k = 1, nlevels-1
! full-level to half-level
qm(k)=0.5*(hum(k)+hum(k+1))
end do
dlp(1:nlevels-1) = log(pf(2:nlevels)) - log(pf(1:nlevels-1))
dp(1:nlevels-1) = pf(2:nlevels) - pf(1:nlevels-1)
! 0.0 find the pressure level index that is closest to
! 1000hPa, 300hPa, 200hPa, and 50hPa respectively
itmp(1:1) = minloc(abs(pf(:)-1000.0))
index1000 = itmp(1)
itmp(1:1) = minloc(abs(pf(:)-300.0))
index300 = itmp(1)
itmp(1:1) = minloc(abs(pf(:)-200.0))
index200 = itmp(1)
itmp(1:1) = minloc(abs(pf(:)-50.0))
index50 = itmp(1)
! 1.0 convert all temperatures to virtual temperatures
! and full-level to half-level
! ----------------------------------------------------
do k = 1, nlevels-1
tv(k) = 0.5*(temp(k)+temp(k+1))*(1.0+0.608*qm(k))
end do
if ( (1000.0 > pf(nlevels)) ) then
add_thk = kth*( tv(nlevels-1)*(log(1000.0)-log(pf(nlevels))) ) ! approximation
else
add_thk = 0.0
end if
! 2.0 construct averages for nesdis thick layers
! ----------------------------------------------
pred(1) = kth*sum( tv(index300+1:index1000)*dlp(index300+1:index1000) ) + add_thk
pred(2) = kth*sum( tv(index50+1:index200)*dlp(index50+1:index200) )
pred(3) = t_skin
pred(4) = kpc*sum( qm(1:nlevels-1)*dp(1:nlevels-1) )
if (trace_use) call da_trace_exit("da_predictor_rttov")
end subroutine da_predictor_rttov