Data Description:

Appended below are JMA values of effective atmospheric angular
momentum functions.  Data are given up to four times daily (there may
be 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 8 values of X1, X2 and X3,
respectively.  The 8 values are those for wind-northern hemisphere to
100 mb, wind-northern hemisphere to top of model (10 mb in the case of
JMA), pressure-northern hemisphere, and pressure + inverted
barometer-northern hemisphere, and the same four terms for the
southern hemisphere.  All data values are true values multiplied by
10**7.  Note that the inverted barometer correction involves applying
the mean atmospheric surface pressure over the whole world ocean to
every point over the world ocean.  Missing data are either given the
special value of -99.0, or are absent from the record.

Data prior to April, 1997 are contianed in file aam.jma, data since
that date are in file aam.jma.2.  Please note that JMA X3 data prior
to April, 1997 has an opposite sign to the X3 terms since.


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

      read(lunit,101) iyear, imonth, iday, ihour
      read(lunit,102) x1w100nh,  x1w10nh,    x1pnh, x1wpibnh, x1w100sh,
     +                 x1w10sh,    x1psh,  x1pibsh
      read(lunit,102) x2w100nh,  x2w10nh,    x2pnh,  x2pibnh, x2w100sh,
     +                 x2w10sh,    x2psh,  x2pibsh
      read(lunit,102) x3w100nh,  x3w10nh,    x3pnh,  x3pibnh, x3w100sh,
     +                 x3w10sh,    x3psh,  x3pibsh
 101  format(1x,4i4)
 102  format(8f10.5)


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.