W3FA09

The W3FA09 function computes saturation vapor pressure in kilopascals.

USAGE:  VP = W3FA09 (TK)

   Input argument list:
     TK    REAL*8 TEMPERATURE IN KELVINS. IF TK < 223.16, THE VALUE
           223.16 WILL BE USED.  IF TK > 323.16, THE VALUE 323.16
           WILL BE USED AS THE ARGUMENT. 'TK' ITSELF IS UNCHANGED.

   Output argument list:
     VP    SATURATION VAPOR PRESSURE IN KILOPASCALS.
           0.0063558 < VP < 12.3395

REMARKS:
        W3FA09 may be declared real*8 so that a real*8 value is 
        returned, but no increase in accuracy is implied.