DS126.0 represents a dataset implemented and computed by NCAR's Data Support Section, and forms an essential part of efforts undertaken in late 2004, early 2005, to produce an archive of selected segments of ERA-40 on a standard transformation grid.

In this case, forty seven ERA-40 monthly mean (designated as "MODA" or "moda" below) surface and single level analysis variables were transformed from a reduced N80 Gaussian grid to a 256x128 regular Gaussian grid. (These are further designated as "SURFACE", or "SURFACE/SINGLE LEVEL", or "SFC/sfc", variables below.) All fields were transformed using routines from the ECMWF EMOS library, including 10 meter winds which were treated as scalars because of a lack of 10 meter spectral vorticity and divergence. A missing value of 9.999e+20 occurs in the sea surface temperature and sea ice (SSTK and CI) fields to mask grid points occurring over land. Fields formerly archived as whole integers, such as vegetation indices and cloud cover, occur as integers plus a fractional part in the T85 version due to interpolation.

Twenty seven ERA-40 monthly mean (designated as "MODA" or "moda" below) surface and single level 6-hour forecast variables were transformed from a reduced N80 Gaussian grid to a 256x128 regular Gaussian grid. (These are further designated as "OTHER", or "othr", variables below.) Four of the variables are "instantaneous" variables, and the remaining twenty three variables are "accumulated" over the 6-hour forecast time. Divide the accumulated variables by 21600 seconds to obtain instantaneous values. (Multiplication by minus one may also be necessary to match the sign convention one is accustomed to.) All fields were transformed using routines from the ECMWF EMOS library, including three pairs of stresses which were treated as scalars because of a lack of spectral precursors.

In addition, all corresponding 00Z, 06Z, 12Z, and 18Z monthly mean surface and single level analysis variables and 6-hour forecast variables were also transformed to a T85 Gaussian grid (designated as "MNLY", "mnly", or "mnth" below)

All forecast variables are valid 6 hours after the forecast was initiated. Thus, 00Z 6-hour forecast evaporation is valid at 06Z. Divide the accumulated variables by 21600 seconds to obtain instantaneous values. (Multiplication by minus one may also be necessary to match the sign convention one is to.)

The choice of a T85 Gaussian grid was based on considerations of limiting the volume of new data generated to a moderate level, and to match the horizontal resolution of the Community Atmosphere Model (CAM) component of NCAR's Community Climate System Model (CCSM).