*     Returns saturation vapor pressure (in Pa) as function of
*     temperature (in K).

      function es(t)
      real tc, es, t
      if (t .lt. 150.0 .or. t .gt. 320.0) then
         stop 'Temperature out of range in es(T)'
      endif
      tc = t - 273.15
      es = 611.2*exp(17.67*tc/(tc+243.5))
      return
      end