| Documentation |
The specifications of the globally gridded meteorological data are:
Time resolution: 6 hours, 00/06/12/18 UTC
Horizontal resolution: 1 deg spacing in latitude and longitude
Vertical disretization:
1980-01-01 - 2001-12-31: 23 pressure levels from ERA40-reanalysis
2002-01-01 - 2007-11-05 (06 UTC): 21 pressure levels from operational data
2007-11-05 (12 UTC) - now: 25 pressure levels from operational data,
in [hPa]: 1/2/3/5/7/10/20/30/50/70/100/150/200/250/300/400/
500/700/800/850/900/925/950/1000
Preprocessing the ECMWF data for the calculation of AAM involves
the following models:
Digital elevation model:
ETOPO5 (http://www.ngdc.noaa.gov/mgg/global/etopo5.html)
Geopotential model:
EGM96 (Lemoine et. al, 1998). Geoid undulations are
determined up to degree and order 360, for gravity
values the expansion is truncated at degree 2.
Consistently, WGS84 is employed as horizontal datum and the
height system is orthometric. The node data of each meteorological
parameter are averaged to a mean value for every 1 deg cell.
The three components of AAM are split up into matter (components
c12, c23, c33 of the inertia tensor, units [kg m2]) and motion
terms (relative angular momentum, units [kg m2 / sec]).
Depending on the calculation scheme applied for numerical
integration, two files are available for each day:
yyyymmdd_ps_vxxx.aam and yyyymmdd_dp_vxxx.aam, where vxxx
refers to the version number of the produced files.
Columns 1-6 have the same content in both files:
1-4: Year, month, day, hour of the initialization epoch
5: Forecast step in hours
6: mjd of the forecasted epoch
Remaining columns in yyyymmdd_ps_vxxx.aam:
7-9: non-IB mass terms, determined as double integral over
surface pressure
10-12: IB mass terms, --//--
Remaining columns in yyyymmdd_dp_vxxx.aam:
7-9: non-IB mass terms, determined as volume integral over
pressure increments
10-12: motion terms, --//--
http://ggosatm.hg.tuwien.ac.at/ROTATION/AAM/VERSION1/readme_aamv1.txt |
| Data |
YYYY MM DD HH, forecast hours, MJD, non-IB mass terms (x,y,z), motion terms (x,y,z) |
| Reference |
Schindelegger M., Böhm J., Salstein D., Schuh H. High-resolution
atmospheric angular momentum functions related to Earth rotation
parameters during CONT08. Journal of Geodesy,
doi: 10.1007/s00190-011-0458-y, 2011.
Boehm J., Mendes Cerveira P.J., Englich S., Schuh H. Atmosphere
Angular Momentum Time Series for CONT05, In Finkelstein A.,
Behrend D. (eds), The 5th International VLBI Servie for Geodesy
and Astrometry General Meeting Proceedings, pages 14-18, 2008.
Salstein D.A., Kann D.M., Miller A.J., Rosen R.D. The Sub-bureau
for Atmospheric Angular Momentum of the International Earth Rotation
Service: A Meteorological Data Center with Geodetic Applications.
Bulletin American Meteorological Society, 74:67-80, 1993
Lemoine F.G., Kenyon S.C., Factor J.K., Trimmer R.G., Pavlis N.K.,
Chinn D.S., Cox C.M., Klosko S.M., Luthcke S.B., Torrence M.H.,
Wang Y.M., Williamson R.G., Pavlis E.C., Rapp R.H. and Olson T.R.
The Development of the Joint NASA GSFC and NIMA Geopotential Model
EGM96, NASA Goddard Space Flight Center, Greenbelt, Maryland,
20771 USA, July 1998. |
1995_dp_v001.aam