BRTEMP: Brightness Temperature

In CORe's post files, there is a field that wgrib2 labels as BRTEMP
which is the long-wave brightness temperature. This field may be
labelled as BRTMP (short-wave brightness temperature) in some
NCEP model output and some older CORe archives.

The BRTEMP field is single level field (top of atmosphere), and
one may wonder why it is not part of the flx files.  It isn't
because the flx file is created from the model output, and
BRTEMP is not calculated by the model. BRTEMP is calculated by
the post which uses the CRTM (Community Radiative Transfer Model) 
which is different from the radiation model used by the model 
(RRTM developed by AER).  In theory one can convert between the
OLR and brightness temperature.  However it is difficult to do
a direct comparison because the OLR is a 3 hour average and the
brightness temperature is instantaneous because it based on a
snapshot of the temperatures and clouds.