!              Erythemal Irradiance
!              Eqn 6723  y=a+bx^2+cx^4+dx^6+ex^8
!               altitude from 0 to 4 km    e.g., U0 is 0 km u4 is 4 km
!               x = sza in degrees   x2=x*x                  0 to 80
!                Fery = U * (O3/200)**(-R)           O3  = ozone 100 to 600 DU

  R0=1.156052570367475D0+x2*(1.800779814654073D-05+
    x2*(-3.002170350795624D-09+x2*(-2.618973217138668D-13+
    x2*-5.962141832425528D-17)));

  U0=0.4631857584050039D0+x2*(-0.0001822463902435957D0+
    x2*(2.608180492051142D-08+x2*(-1.512730491209405D-12+
    x2*2.372517703335847D-17)));

  R1=1.158813799843628D0+x2*(1.798228311550313D-05+
    x2*(-2.341405388985520D-09+x2*(-4.940911355497962D-13+
    x2*-3.662757312824093D-17)));

  U1=0.4864803303362002D0+x2*(-0.0001902024798369626D0+
    x2*(2.681607208941479D-08+x2*(-1.496297969816634D-12+
    x2*1.994080269355319D-17)));

  R2=1.161808588741204D0+x2*(1.799758520126839D-05+
    x2*(-1.915067132118472D-09+x2*(-6.597361325385819D-13+
    x2*-1.812061992439043D-17)));


  U2=0.5079192885066458D0+x2*(-0.0001973003406543994D0+
    x2*(2.746439766508111D-08+x2*(-1.487461804021105D-12+
    x2*1.729752421529277D-17)));


  R3=1.164645140734949D0+x2*(1.827192802554558D-05+
    x2*(-1.622244346840331D-09+x2*(-7.781258305173713D-13+
    x2*-5.305366160696516D-18)));

  U3=0.5284067670054730D0+x2*(-0.0002038689301215864D0+
    x2*(2.803667684454433D-08+x2*(-1.479493136552102D-12+
    x2*1.519495178354487D-17)));

  R4=1.167556550039093D0+x2*(1.857640755944660D-05+
    x2*(-1.366086322882707D-09+x2*(-8.801168565606416D-13+
    x2*4.965027748661278D-18)));

  U4=0.5486120641125880D0+x2*(-0.0002101682613803770D0+
    x2*(2.851449388190919D-08+x2*(-1.457148378904343D-12+
    x2*1.228110040940689D-17)));