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!******************************************
!
! subroutine EFFHT(HO,HV,SIGO,SIGV,MU,ZCLD,HDN,HUP,HDNinF,HUPinF)
!
! This subroutine returns "effective emitting heights" for an atmosphere
! with gaseous absorption approximated by two exponentially-decaying
! profiles with distinct scale heights. For applications at
! SSM/I frequencies (i.e., 19, 22, 37, 86 GHz), these absorption profiles
! correspond to water vapor and dry air absorption, respectively.
!
! Input parameters: HO, HV -- scale heights of absorption corresponding to
! dry air and water vapor (km):
!
! SIGO, SIGV -- total optical depth due to each constituent
! (the present model is valid only for (sigo+sigv < 1.0) )
!
! MU -- secant(theta), where theta is the path angle from vertical
!
! ZCLD -- upper limit (km) of the atmospheric layer for which
! hdn, hup are to be calculated. Layer extends down to the
! surface. These parameters permit the separate calculation
! brightness temperature contributions from a lower and
! upper atmospheric layer, separated by a cloud layer at
! height zcld.
!
! Output parameters:
!
! HDN, HUP -- "effective emitting height" of an atmospheric layer
! bounded below by the surface and above at height zcld.
! "Effective emitting temperature" for upward and downward
! microwave radiation emitted by that layer is then given by
! (Ta - gamma*hup) and (Ta - gamma*hdn), respectively, where
! Ta and gamma are effective surface temperature (deg K)
! and lapse rate (K / km), respectively. Brightness temperatures
! due to emission from this layer are then (1 - tau)(Ta - gamma*hup)
! and (1 - tau)(Ta - gamma*hdn), respectively, where tau is
! the slant path transmittance of the layer at angle theta
!
! HDinF,HUPinF -- same as hdn and hup, but for the entire
! atmosphere (i.e., zcld set to infinity)
!
!
! This version of EFFHT executes 83 floating point multiplications,
! 11 floating point divisions, and 2 calls to exp() .
!
!----------------------------------------------
<A NAME='EFFHT'><A href='../../html_code/ssmi/effht.inc.html#EFFHT' TARGET='top_target'><IMG SRC="../../gif/bar_red.gif" border=0></A>
subroutine effht(ho,hv,sigo,sigv,mu,zcld,hdn,hup,hdninf,hupinf) 2
!
real ho,hv,sigo,sigv,mu,zcld,gint,zgint,hint,zhint, &
ginf,zginf,hinf,zhinf,hdn,hup,hdninf,hupinf
!
real hoinv,hvinv,chio,chiv,ezho,ezhv,alpha,alph2,alph3
real beta,beta2,beta3,mu2,mualph,cplus,cmin,dplus,dmin
real chiov,chivv,chioo,chioov,chiovv,chiooo,chivvv
real h11,h21,h12
real sigoo,sigov,sigvv,sigooo,sigoov,sigovv,sigvvv
real ezhoo,ezhov,ezhvv,ezhooo,ezhoov,ezhovv,ezhvvv
real s,sprim,t,tprim,u,uprim,term1,term2,term3
real halfmu,halfmu2,sixthmu2,etnthmu2,quartmu
!
!
hoinv = 1.0d0/ho
hvinv = 1.0d0/hv
chio = zcld*hoinv
chiv = zcld*hvinv
ezho = sigo*exp(-chio)
ezhv = sigv*exp(-chiv)
alpha = sigo + sigv
alph2 = alpha*alpha
alph3 = alpha*alph2
beta = ezho + ezhv
beta2 = beta*beta
beta3 = beta*beta2
!
mu2 = mu*mu
halfmu = 0.5d0*mu
sixthmu2 = mu2/6.0d0
etnthmu2 = mu2/18.0d0
quartmu = 0.25d0*mu
halfmu2 = 0.5d0*mu2
mualph = mu*alpha
cplus = 1.0d0 + mualph
cmin = 1.0d0 - mualph
dplus = halfmu2*alph2
dmin = dplus
dplus = cplus + dplus
dmin = cmin + dmin
!
h11 = hoinv + hvinv
h21 = 1.0d0/(h11 + hvinv)
h12 = 1.0d0/(h11 + hoinv)
h11 = 1.0d0/h11
chiov = 1.0d0 + chio + chiv
chioo = 1.0d0 + chio + chio
chivv = 1.0d0 + chiv + chiv
chioov = chioo + chiv
chiovv = chio + chivv
chiooo = chioo + chio
chivvv = chivv + chiv
chio = 1.0d0 + chio
chiv = 1.0d0 + chiv
sigov = sigo*sigv
sigoo = sigo*sigo
sigvv = sigv*sigv
sigooo = sigoo*sigo
sigoov = sigoo*sigv
sigovv = sigo*sigvv
sigvvv = sigvv*sigv
ezhoo = ezho*ezho
ezhov = ezho*ezhv
ezhvv = ezhv*ezhv
ezhovv = ezho*ezhvv
ezhoov = ezhoo*ezhv
ezhooo = ezhoo*ezho
ezhvvv = ezhvv*ezhv
s = sigo*ho + sigv*hv
sprim = ezho*ho*chio + ezhv*hv*chiv
t = sigoo*ho + 4.0d0*sigov*h11 + sigvv*hv
tprim = ezhoo*ho*chioo + 4.0d0*ezhov*h11*chiov + ezhvv*hv*chivv
u = sigooo*ho+9.0d0*(sigovv*h21+sigoov*h12)+sigvvv*hv
uprim = ezhvvv*hv*chivvv + &
9.0d0*(ezhovv*h21*chiovv + ezhoov*h12*chioov) + &
ezhooo*ho*chiooo
!
term1 = s - sprim
term2 = quartmu*(t - tprim)
term3 = etnthmu2*(u - uprim)
zgint = dmin*term1 + cmin*term2 + term3
zhint = -dplus*term1 + cplus*term2 - term3
term2 = quartmu*t
term3 = etnthmu2*u
zginf = dmin*s + cmin*term2 + term3
zhinf = -dplus*s + cplus*term2 - term3
term1 = alpha - beta
term2 = halfmu*(alph2 - beta2)
term3 = sixthmu2*(alph3 - beta3)
gint = dmin*term1 + cmin*term2 + term3
hint = -dplus*term1 + cplus*term2 - term3
term2 = halfmu*alph2
term3 = sixthmu2*alph3
ginf = dmin*alpha + cmin*term2 + term3
hinf = -dplus*alpha + cplus*term2 - term3
hdn = zgint/gint
hup = zhint/hint
hdninf = zginf/ginf
hupinf = zhinf/hinf
end subroutine effht