IERS GGFC Operational Product

Hydrospheric Effective Angular Momentum (EAM) Functions

Data access

Atmosphere (AAM), ocean (OAM), and continental hydrology (HAM) angular momentum
Earth rotation effective angular momentum (EAM) functions for hydrospheric mass transports are generated with the Ocean Model for Circulation and Tides (OMCT) and the hydrological Land Surface Discharge Model (LSDM) using atmospheric forcing data from the European Centre for Medium-Range Weather Forecasts (ECMWF).The models are combined to ensure mass conserving freshwater fluxes among the three subsystems atmosphere, oceans, and continental hydrosphere in order to represent a closed global hydrological cycle. The model system is forced with 4 different ECMWF atmospheric data sets:

ECMWF ERA-40 re-analysis 1958 – 2001:
yearly AAM, HAM, OAM files
ERA40.yyyy.aam
ERA40.yyyy.ham
ERA40.yyyy.oam

ECMWF ERA-Interim re-analysis 1989 – 2008:
yearly AAM, HAM, OAM files
ERAinterim.yyyy.aam
ERAinterim.yyyy.ham
ERAinterim.yyyy.oam

operational ECMWF 2001 – now:
yearly AAM, HAM, OAM files
opECMWF.yyyy.aam
opECMWF.yyyy.ham
opECMWF.yyyy.oam
rl04.yyyy.oam

The current year is updated daily with about 4-5 days latency for the latest day. RL04 data is calculated without any freshwater fluxes from the continental hydrology consistent with the OMCT GRACE dealising product AOD RL04 (Flechtner, 2007). RL04 was terminated im May 2012. RL05 OAM files will be available soon.

ECMWF 10-day forecasts:
daily AAM, HAM, OAM forecasts
f10d.yyyy_ddd.aam
f10d.yyyy_ddd.ham
f10d.yyyy_ddd.oam

Since beginning of 2012 GFZ German Research Centre for Geosciences section 1.3 is accepted as GGFC Operational Product Center of the International Earth Rotation and Reference System Service (IERS).

Please have a look on the format description of the EAM files and the coefficients applied in the EAM calculation.

References  

• Dobslaw, H., R. Dill, A. Groetzsch, A. Brzezinski, and M. Thomas (2010), Seasonal polar motion excitation from numerical models of atmosphere, ocean, and continental hydrosphere,J. Geophys. Res., doi:10.1029/2009JB007127
• Dill, R. and H. Dobslaw (2010), Short-term polar motion forecasts from earth system modeling data, J. of Geodesy 84, pp 529-536, doi:10.1007/s00190-010-0391-5.
• Dill, R. (2008), Hydrological model LSDM for operational Earth rotation and gravity field variations.Scientific Technical Report STR08/09, GFZ Potsdam, Germany, 35p.
• Dill, R. (2009), Hydrological induced Earth rotation variations from stand-alone and dynamically coupled simulations.Proceedings of LesJournées 2008 "Systèmes de RéférenceSpatio-Temporels", Dresden.
• Dobslaw, H. and M. Thomas (2007), Simulation and observation of global oceanmass anomalies. J. Geophys. Res., 112, C05040, doi:10.1029/2006JC004035.
• Dobslaw, H. and M. Thomas (2005), Atmospheric induced oceanic tides from ECMWF forecasts, Geophys. Res. Lett., 32, L10615.
• Dobslaw, H. and M. Thomas (2007), Impact of river run-off on global ocean mass redistribution, Geophys. J. Int., 168, 2, 527-532.
• Dobslaw, H. and M. Thomas (2007), Simulation and observation of global ocean mass anomalies, J. Geophys. Res., 112, C05040.