ERA40 T85 Analysis Fields on Model Levels, created at NCAR

In this case, ERA-40 6-hourly upper air variables on 60 model levels were transformed from either spherical harmonics (surface geopotential, temperature, vertical velocity, vorticity, logarithm of surface pressure, divergence), or a reduced N80 Gaussian grid (specific humidity, ozone mass mixing ratio, cloud liquid water content, cloud ice water content, cloud cover), to a 256 by 128 regular Gaussian grid at T85 spectral truncation.

In addition, horizontal wind components were derived from spectral vorticity and divergence and also archived on a T85 Gaussian grid. All scalar fields were transformed using routines from the ECMWF EMOS library, whereas the horizontal winds were obtained using NCAR's SPHEREPACK library. 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) [cesm.ucar.edu/models/atm-cam/] component of NCAR's Community Climate System Model (CCSM).