The data are coefficients of a triangular truncation to wave number 4
(T4) and the zonal components to wave 20 (R20Z) for surface pressure
(sfc p), and for sfc p with an inverted barometer correction, from the
NCEP/NCAR Reanalyses.  The arrays are ordered as follows:

1) T4 coefficients of sfc p (30 coefficients)

2) R20Z zonal coefficients of sfc p to wave 20 (21 coefficients)

The T4 field is originally made up of 15 COMPLEX words, which can be
expressed as 30 REAL words.  The zonal coefficients only contain the
real component of the complex word.  Therefore, when the 30 REAL
coefficients of the T4 field are written, five of these numbers are
zero.  The coefficients are stored as follows:


     m(zonal wave number)
   A                         i.e., ((a(n,m),n=m,4),m=0,4)
     n(total wave number)

The array of zonal coefficients to wave 20 consist of 21 REAL numbers,
the first five of which can be found in the T4 array.

The data are given four times daily. The following FORTRAN code
fragment could be used to read one record of data:

      dimension pcoeff(51),pcoeffib(51)
      open(11,file='pcoeff.ncep.reanalysis.1975.1998')
      read(11,101) iyear,imonth,iday,ihour
      read(11,102) pcoeff
      read(11,102) pcoeffib
 101  format(1x,4i4)
 102  format((5(1x,e15.8))