[RegCNET] solin

[Jonathan Winter]

While comparing two runs, one using an older version (summer 2004) of
the model that I had modified and the other a newer version (~ fall
2004) that has not been modified, I noticed a difference in solin, which
is top of atmosphere instantaneous incident solar.  It didn't seem
logical that this had changed between model revisions, so with some
print statements I found the formulation of calday, which is used to
calculate eccf (eccentricity factor) which in turn is part of the
equation for solin, is different.  In the older version, it's:

calday = dble(julday)+(NNNNNN-NSTRT0)/4. + (xtime/60.+gmt)/24.

but in the newer version (as well as in the latest release I think)
it's:

calday= dble(julday)+mod(NNNNNN-NSTRT0,4)/4. + (xtime/60.+gmt)/24.

The top statement seems to keep track of the calendar day correctly
(where noon on Jan. 15 would be 15.5) while the lower seems stuck on Jan
1st with the fraction of whatever day it is (Jan. 15 at noon would be
1.5)  The difference in calday changes eccf which changes solin.  

Does anybody know why this was changed, which statement is right, and if
it's the bottom statement, why?  Thanks in advance for the information.

jonathan