hi max,
here is the rain evap code that i checked out offline against
what we are running now in the GCM. The approximation to use
a square root instead of the .578 exponent gave some differences
that i thought were a bit too large, so i left the .578 power
for now. the other approximation, for the exponential, was okay,
but i left the 'exact' code there as well...
andrea