Nudds et al NCEP Tair Correction (1997-2004)
============================================

* 96-month time series + 2 end points = 98 months:

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

The corrections for the two endpoints are zero everywhere.
This is needed to get no correction for dates outside of 1997-2004
when using the CCSM data (atmosphere) model input stream 
time interplation/extrapolation functionality to give 

* 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.

--------------------------------------------------------------------------------
This readme corresponds to this data file:

unix> pwd
/CESM/cseg/inputdata/atm/datm7/CORE2

unix> ls -l CORE2.t_10.ArcFactor.T62.1997-2004.nc
-rw-r--r--    1 kauff    cseg        8740592 Dec 08 2010  CORE2.t_10.ArcFactor.T62.1997-2004.nc

unix> ncdump -h CORE2.t_10.ArcFactor.T62.1997-2004.nc
netcdf CORE2.t_10.ArcFactor.T62.1997-2004 {
dimensions:
        time = UNLIMITED ; // (98 currently)
        nj = 94 ;
        ni = 192 ;
        nv = 4 ;
        lon = 192 ;
        lat = 94 ;
variables:
        double time(time) ;
                time:long_name = "Time corresponding to monthly mean TarcFactor" ;
                time:calendar = "noleap" ;
                time:units = "days since 1997-01-01 00:00:00" ;
                time:_FillValue = -9999. ;
        double xc(nj, ni) ;
                xc:long_name = "longitude of grid cell center" ;
                xc:units = "degrees east" ;
        double yc(nj, ni) ;
                yc:long_name = "latitude of grid cell center" ;
                yc:units = "degrees north" ;
        double xv(nj, ni, nv) ;
                xv:long_name = "longitude of grid cell verticies" ;
                xv:units = "degrees east" ;
        double yv(nj, ni, nv) ;
                yv:long_name = "latitude of grid cell verticies" ;
                yv:units = "degrees north" ;
        int mask(nj, ni) ;
                mask:long_name = "domain mask" ;
                mask:units = "unitless" ;
        double area(nj, ni) ;
                area:long_name = "area of grid cell in radians squared" ;
                area:units = "area" ;
        double lon(lon) ;
                lon:units = "degrees_east" ;
                lon:modulo = 360. ;
                lon:point_spacing = "even" ;
                lon:axis = "X" ;
        double lat(lat) ;
                lat:units = "degrees_north" ;
                lat:point_spacing = "uneven" ;
                lat:axis = "Y" ;
                lat:bounds = "LAT_bnds" ;
        float TarcFactor(time, lat, lon) ;
                TarcFactor:units = "Kelvin" ;
                TarcFactor:long_name = "Nudds_et_al Arctic air temp correction, Jan 1997 - Dec 2004" ;
                TarcFactor:description = "CorrectedNCEP-NCEP" ;
                TarcFactor:_FillValue = -999.f ;

// global attributes:
                :title = "Nudds et al Arctic NCEP air temperature correction" ;
                :comment = "Correction obtained via personal communication from Shannon Nudds (shannonnudds@yahoo.ca); following Nudds et al recommendation, corrections for July, August, September have been set to 0." ;
                :reference = "Nudds, Dupont, and Peterson, 2010: Errors in the NCEP/NCAR Reanalysis-1 air temperature data in the Arctic between 1997 and 2004, and a post processing correction.  Canadian Technical Report of Hydrography and Ocean Sciences, 266, Bedford Institute of Oceanography, Dartmouth, N.S." ;
                :created_by = "S. Yeager (yeager@ucar.edu), Wed Dec  8 12:31:11 MST 2010" ;
}