real function dstn1 
     i         (rn1,rn2)
c
c     + + + PURPOSE + + +
c     Computes the distance from the mean of a normal distribution,
c     with mean = 0 and standard deviation = 1, given two random numbers.
c
c     + + + ARGUMENT DECLARATIONS + + +
      real rn1,rn2
c
c     + + + ARGUMENT DEFINITIONS + + +
c     rn1         - ??? -- used for precip gamma dsn
c     rn2         -
c
c     + + + END SPECIFICATIONS + + +
c
      dstn1=sqrt(-2.0*alog(rn1))*cos(6.283185*rn2)
c ---- range check:
      if(dstn1 .le. -10.0) dstn1 = -10.0
      if(dstn1 .ge. 10.0) dstn1 = 10.0
c
      return
      end