Data Description:

Data are UKMO values of effective atmospheric angular momentum
functions.  Data are given up to twice daily (there are gaps in
the record), and each epoch consists of a header record giving the
date and time, and three data records.

The three lines after the header contain 6 values of X1, X2 and X3,
respectively.  The 6 values are those for wind-northern hemisphere to
top of model (~25 mb for the UKMO), pressure-northern hemisphere, and
pressure + inverted barometer-northern hemisphere and the same three
terms for the southern hemisphere.  All data values are true values
multiplied by 10**7.  Presently, the UKMO does not calculate the
inverted barometer term, and these are given a missing indicator of
-99.0.  Other missing data are either given the missing indicator, or
are absent from the record.  Data prior to April, 1997 are contined in
file aam.ukmo, data since are in file aam.ukmo.2.


Each days data may be read with the following FORTRAN code:

      read(lunit,101) iyear, imonth, iday, ihour
      read(lunit,102)  x1wnh,    x1pnh,  x1pibnh,
     +                 x1wsh,    x1psh,  x1pibsh
      read(lunit,102)  x2wnh,    x2pnh,  x2pibnh,
     +                 x2wsh,    x2psh,  x2pibsh
      read(lunit,102)  x3wnh,    x3pnh,  x3pibnh,
     +                 x3wsh,    x3psh,  x3pibsh
 101  format(1x,4i4)
 102  format(6f10.5)


Information about atmospheric excitation for Earth rotation/polar
motion and related fields are supplied by Salstein, et al., (1993):

Salstein, D.A., D.M. Kann, A.J. Miller, R.D. Rosen, 1986: The
Sub-bureau for Atmospheric Angular Momentum of the International Earth
Rotation Service: A Meteorological Data Center with Geodetic
Applications. Bull. Amer. Meteor. Soc., 74, 67-80.