var/da/da_ssmi/effang.inc

   1       subroutine effang(ifreq,theta,gx2,sigma,effangv,effangh)
   2 !
   3 ! Calculated the effective zenith angle of reflected microwave radiation
   4 ! at SSM/I frequencies for vertical and horizontal polarization
   5 !
   6       real theta, gx2,sigma,effangv,effangh
   7       integer ifreq
   8       real gg,ggg,xx,xd,z1,z2,z3,z4,z5,z6,alnthv
   9       real alnthh,angv,angh,y,alnsig,dth
  10 !
  11       real c19v,c19h,c22v,c22h,c37v,c37h,c85v,c85h
  12       real s19v(6),s19h(6),s22v(6),s22h(6), &
  13            s37v(6),s37h(6),s85v(6),s85h(6)
  14 !
  15       data c19v,c19h,c22v,c22h,c37v,c37h,c85v,c85h &
  16         /-.5108,.5306,-.5108,.5306,-.6931,.1823,-.9163,.3000/
  17       data s19v /.225E+2,.698E+2,-.238E+2,-.648E+1,.402E+0,.262E+1/
  18       data s19h /.743E+1,.507E+2,-.206E+2,-.191E+1,.648E-1,.291E+1/
  19       data s22v /.249E+2,.701E+2,-.240E+2,-.714E+1,.405E+0,.256E+1/
  20       data s22h /.498E+1,.442E+2,-.190E+2,-.129E+1,.803E-2,.277E+1/
  21       data s37v /.215E+2,.573E+2,-.211E+2,-.670E+1,.443E+0,.253E+1/
  22       data s37h /.869E+1,.571E+2,-.257E+2,-.302E+1,.237E+0,.386E+1/
  23       data s85v /.116E+2,.263E+2,-.101E+2,-.358E+1,.270E+0,.175E+1/
  24       data s85h /.736E+1,.568E+2,-.254E+2,-.248E+1,.196E+0,.387E+1/
  25 !
  26       if (gx2 .le. 0.0 .or. sigma .le. 0.0) then
  27         effangv = theta
  28         effangh = theta
  29         return
  30       end if
  31       alnsig = alog(sigma)
  32       gg = gx2*gx2
  33       ggg = gg*gx2
  34       if (ifreq .eq. 1) then
  35          xd = alnsig - c19v
  36          xx = xd*xd
  37          z1 =  xx*ggg
  38          z2 =  xd*ggg
  39          z3 =  xd*gg
  40          z4 =  xx*gg
  41          z5 =  xx*gx2
  42          z6 =  xd*gx2
  43          alnthv = s19v(1)*z1 + s19v(2)*z2 +s19v(3)*z3 + &
  44            s19v(4)*z4 + s19v(5)*z5 + s19v(6)*z6
  45          alnthv = alnthv + 3.611
  46 !
  47          xd = alnsig - c19h
  48          xx = xd*xd
  49          z1 =  xx*ggg
  50          z2 =  xd*ggg
  51          z3 =  xd*gg
  52          z4 =  xx*gg
  53          z5 =  xx*gx2
  54          z6 =  xd*gx2
  55          alnthh = s19h(1)*z1 + s19h(2)*z2 +s19h(3)*z3 + &
  56            s19h(4)*z4 + s19h(5)*z5 + s19h(6)*z6
  57          alnthh = alnthh + 3.611
  58       else if (ifreq .eq. 2) then
  59          xd = alnsig - c22v
  60          xx = xd*xd
  61          z1 =  xx*ggg
  62          z2 =  xd*ggg
  63          z3 =  xd*gg
  64          z4 =  xx*gg
  65          z5 =  xx*gx2
  66          z6 =  xd*gx2
  67          alnthv = s22v(1)*z1 + s22v(2)*z2 +s22v(3)*z3 + &
  68            s22v(4)*z4 + s22v(5)*z5 + s22v(6)*z6
  69          alnthv = alnthv + 3.611
  70 !
  71          xd = alnsig - c22h
  72          xx = xd*xd
  73          z1 =  xx*ggg
  74          z2 =  xd*ggg
  75          z3 =  xd*gg
  76          z4 =  xx*gg
  77          z5 =  xx*gx2
  78          z6 =  xd*gx2
  79          alnthh = s22h(1)*z1 + s22h(2)*z2 +s22h(3)*z3 + &
  80            s22h(4)*z4 + s22h(5)*z5 + s22h(6)*z6
  81          alnthh = alnthh + 3.611
  82       else if (ifreq .eq. 3) then
  83          xd = alnsig - c37v
  84          xx = xd*xd
  85          z1 =  xx*ggg
  86          z2 =  xd*ggg
  87          z3 =  xd*gg
  88          z4 =  xx*gg
  89          z5 =  xx*gx2
  90          z6 =  xd*gx2
  91          alnthv = s37v(1)*z1 + s37v(2)*z2 +s37v(3)*z3 + &
  92            s37v(4)*z4 + s37v(5)*z5 + s37v(6)*z6
  93          alnthv = alnthv + 3.611
  94 !
  95          xd = alnsig - c37h
  96          xx = xd*xd
  97          z1 =  xx*ggg
  98          z2 =  xd*ggg
  99          z3 =  xd*gg
 100          z4 =  xx*gg
 101          z5 =  xx*gx2
 102          z6 =  xd*gx2
 103          alnthh = s37h(1)*z1 + s37h(2)*z2 +s37h(3)*z3 + &
 104            s37h(4)*z4 + s37h(5)*z5 + s37h(6)*z6
 105          alnthh = alnthh + 3.611
 106       else if (ifreq .eq. 4) then
 107          xd = alnsig - c85v
 108          xx = xd*xd
 109          z1 =  xx*ggg
 110          z2 =  xd*ggg
 111          z3 =  xd*gg
 112          z4 =  xx*gg
 113          z5 =  xx*gx2
 114          z6 =  xd*gx2
 115          alnthv = s85v(1)*z1 + s85v(2)*z2 +s85v(3)*z3 + &
 116            s85v(4)*z4 + s85v(5)*z5 + s85v(6)*z6
 117          alnthv = alnthv + 3.611
 118 !
 119          xd = alnsig - c85h
 120          xx = xd*xd
 121          z1 =  xx*ggg
 122          z2 =  xd*ggg
 123          z3 =  xd*gg
 124          z4 =  xx*gg
 125          z5 =  xx*gx2
 126          z6 =  xd*gx2
 127          alnthh = s85h(1)*z1 + s85h(2)*z2 +s85h(3)*z3 + &
 128            s85h(4)*z4 + s85h(5)*z5 + s85h(6)*z6
 129          alnthh = alnthh + 3.611
 130       end if
 131       angv = 90.0 - exp(alnthv)
 132       angh = 90.0 - exp(alnthh)
 133       y  = 1.0 - 28.0*gx2
 134       if (y .lt. 0.0) y = 0.0
 135       dth = (theta - 53.0)*y
 136       effangv = angv + dth
 137       effangh = angh + dth
 138
 139       end subroutine effang