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subroutine epsalt(f,t,ssw,epsr,epsi) 2
! returns the complex dielectric constant of sea water, using the
! model of Klein and Swift (1977)
!
! Input f = frequency (GHz)
! t = temperature (C)
! ssw = salinity (permil) (if ssw < 0, ssw = 32.54)
! Output epsr,epsi = real and imaginary parts of dielectric constant
real, intent(in ) :: f,t
real, intent(inout ) :: ssw
real, intent(out ) :: epsr,epsi
real :: ssw2,ssw3,t2,t3,es,a,tau,b,delt
real :: beta,sig,delt2,om
complex cdum1,cdum2,cdum3
!
if (ssw .lt. 0.0) ssw = 32.54
ssw2 = ssw*ssw
ssw3 = ssw2*ssw
t2 = t*t
t3 = t2*t
es = 87.134 - 1.949e-1*t - 1.276e-2*t2 + 2.491e-4*t3
a = 1.0 + 1.613e-5*ssw*t - 3.656e-3*ssw + 3.21e-5*ssw2 - &
4.232e-7*ssw3
es = es*a
!
tau = 1.768e-11 - 6.086e-13*t + 1.104e-14*t2 - 8.111e-17*t3
b = 1.0 + 2.282e-5*ssw*t - 7.638e-4*ssw - 7.760e-6*ssw2 + &
1.105e-8*ssw3
tau = tau*b
!
sig = ssw*(0.182521 - 1.46192e-3*ssw + 2.09324e-5*ssw2 - &
1.28205e-7*ssw3)
delt = 25.0 - t
delt2 = delt*delt
beta = 2.033e-2 + 1.266e-4*delt + 2.464e-6*delt2 - &
ssw*(1.849e-5 - 2.551e-7*delt + 2.551e-8*delt2)
sig = sig*exp(-beta*delt)
!
om = 2.0e9*pi*f
cdum1 = cmplx(0.0,om*tau)
cdum2 = cmplx(0.0,sig/(om*8.854e-12))
cdum3 = 4.9 + (es-4.9)/(1.0 + cdum1) - cdum2
epsr = real(cdum3)
epsi = -aimag(cdum3)
end subroutine epsalt