IMPORTANT NOTICE:

The data and documentation files in this area have been substantially
changed as of March 24, 1999.  These changes were made to make the
AAM data Y2K compliant, and to make the data formats more uniform.
Users should note that any programs used to access this data may need
to be modified to accomodate these changes.  To access this data in
the old format, please see the note below.

Major changes made to the files contained here:

1) The date (header) record in all data files now contains four digit
   fields instead of two digit fields, and the year is now given a 
   full four digit representation (e.g. 1999), not two digit (e.g. 99).

2) Documentation is no longer given within the data files.  Documentation
   for the data are given in the 'readme' files, e.g. readme.aam.ncep

3) All data fields are written out to five decimal places only, not to
   six as in previous versions of some of these data files.

4) The missing indicator is now always -99.0, not -99.9 as with previous
   versions of some of these data files.

Note: Until December, 1999, these data files will still be available
in the previous format.  Users wishing access these non-Y2K compliant
data files can do so via anonymous ftp at:

   ftp.aer.com

   cd pub/sbaam

After December, 1999, the non Y2K compliant data will be removed.


Files in this directory:

README: This file.  Last updated December 14, 1999


aam.ecmwf: ASCII file of effective atmospheric angular momentum functions
           (EAMF) from the ECMWF, 1988-1995

aam.ecmwf.2: ASCII file of EAMF from the ECMWF, 1997 and on

aam.jma: ASCII file of EAMF from the JMA, 1993-1996

aam.jma.2: ASCII file of EAMF from the JMA, 1997 and on

aam.ncep: ASCII file of EAMF from NCEP, 1976-1996

aam.ncep.2: ASCII file of EAMF from NCEP, 1997 and on

aam.ukmo: ASCII file of EAMF from the UKMO, 1986-1996

aam.ukmo.2: ASCII file of EAMF from the UKMO, 1997 and on


aam.ncep.reanalysis.1948.1957: ASCII file of EAMF from NCEP/NCAR
                               reanalyses, 1958-1967

aam.ncep.reanalysis.1958.1967: ASCII file of EAMF from NCEP/NCAR
                               reanalyses, 1958-1967

aam.ncep.reanalysis.1968.1978: ASCII file of EAMF from NCEP/NCAR
                               reanalyses, 1968-1978

aam.ncep.reanalysis.1979.1996: ASCII file of EAMF from NCEP/NCAR
                               reanalyses, 1979-1996

aam.ncep.reanalysis.1997: ASCII file of EAMF from NCEP/NCAR reanalyses, 1997

aam.ncep.reanalysis.1998: ASCII file of EAMF from NCEP/NCAR reanalyses, 1998

aam.ncep.reanalysis.1999: ASCII file of EAMF from NCEP/NCAR reanalyses, 1999

aam.ncep.reanalysis.2000: ASCII file of EAMF from NCEP/NCAR reanalyses, 2000


pcoeff.ncep.formulas.ps: PostScript file of formulas relating to the spherical
                         harmonic coefficients of surface pressure

pcoeff.ncep.reanalysis.1975.1998: ASCII file of spherical harmonic 
                                  coefficients of surface pressure, 1975-1998

pcoeff.ncep.reanalysis.1999: ASCII file of spherical harmonic 
                             coefficients of surface pressure, 1999

pcoeff.ncep.reanalysis.2000: ASCII file of spherical harmonic 
                             coefficients of surface pressure, 2000

ftorque.ncep.reanalysis: ASCII file of global friction torque

mtorque.ncep.reanalysis: ASCII file of global mountain torque


readme.aam.ecmwf: Description of ECMWF data

readme.aam.jma: Description of JMA data

readme.aam.ncep: Description of NCEP data

readme.aam.UKMO: Description of UKMO data

readme.aam.ncep.reanalysis: Description of NCEP reanalysis EAMF data

readme.pcoeff: Description of surface pressure coefficient data

readme.torque.ncep.reanalysis: Description of torque data


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.


Please direct any questions or comments regarding this data to:

Peter Nelson
Atmospheric and Environmental Research, Inc.
840 Memorial Dr.
Cambridge, MA 02139

e-mail: pnelson@aer.com