Nudds et al NCEP Tair Correction (1997-2004)
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* 96-month time series + 2 end points = 98 months:

time(0) = 1997-01-01 00:00:00  
time(1) = 1997-01-15 00:00:00  (Jan 1997)
time(2) = 1997-02-15 00:00:00  (Feb 1997)
...
time(96) = 2004-12-15 00:00:00  (Dec 2004)
time(97) = 2005-01-01 00:00:00

The corrections for the two endpoints are zero everywhere.  This
is needed for correct time extrapolation using the CCSM coupler,
to give no correction for dates outside of 1997-2004.
 
* As per Nudds et al tech note, Tair correction is set to 0.0 
everywhere for summer months (Jul, Aug, Sep).  The time stamp
for these months is left at mid-month, so linear time interpolation
does generate some non-zero correction in early July and late September.

* To implement the correction in CCSM, we treat the "TarcFactor"
from CORE2.t_10.ArcFactor.T62.1997-2004.nc as a seperate data stream
which gets (linearly) time-interpolated to the model time step (at
forcing time steps).  Since the factor is "CorrectedNCEP-NCEP", it
is simply added to the NCEP t_10 forcing stream (see line 952 of
datm_comp_mod.F90), after other t_10 corrections are applied.