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A long-term model for non-tidal atmospheric and oceanic mass redistributions and its implications on LAGEOS-derived solutions of Earth's oblateness

Flechtner, F., Thomas, M., König, R. (2008): A long-term model for non-tidal atmospheric and oceanic mass redistributions and its implications on LAGEOS-derived solutions of Earth's oblateness, (Scientific Technical Report STR ; 08/12), Potsdam : Deutsches GeoForschungsZentrum GFZ, 24 S.: Ill., graph. Darst. p.
DOI: http://doi.org/10.2312/GFZ.b103-08123



http://gfzpublic.gfz-potsdam.de/pubman/item/escidoc:8776
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0812.pdf
(Publisher version), 5MB

Authors
http://gfzpublic.gfz-potsdam.de/cone/persons/resource/flechtne

Flechtner ,  Frank
1.2 Global Geomonitoring and Gravity Field , 1.0 Geodesy and Remote Sensing, Departments, GFZ Publication Database, Deutsches GeoForschungsZentrum;
Scientific Technical Report STR, Deutsches GeoForschungsZentrum;
Earth Observing Satellites -2009, Geoengineering Centres, GFZ Publication Database, Deutsches GeoForschungsZentrum;

http://gfzpublic.gfz-potsdam.de/cone/persons/resource/mthomas

Thomas ,  Maik
1.3 Earth System Modelling , 1.0 Geodesy and Remote Sensing, Departments, GFZ Publication Database, Deutsches GeoForschungsZentrum;
Scientific Technical Report STR, Deutsches GeoForschungsZentrum;
Earth Observing Satellites -2009, Geoengineering Centres, GFZ Publication Database, Deutsches GeoForschungsZentrum;

http://gfzpublic.gfz-potsdam.de/cone/persons/resource/koenigr

König ,  Rolf
1.2 Global Geomonitoring and Gravity Field , 1.0 Geodesy and Remote Sensing, Departments, GFZ Publication Database, Deutsches GeoForschungsZentrum;
Scientific Technical Report STR, Deutsches GeoForschungsZentrum;
Earth Observing Satellites -2009, Geoengineering Centres, GFZ Publication Database, Deutsches GeoForschungsZentrum;

Abstract
The dynamic oblateness of the Earth, in terms of the J2 or C20 coefficient of the Earth´s geo-potential has been derived by analysis of LAGEOS Satellite Laser Ranging (SLR) data. Although recent analyses of GRACE (Gravity Recovery and Climate Experiment) mission data of monthly C20 values since 2002 have shown high temporal correlations with LAGEOS results, significant differences still remain. As it is common practice in GRACE data processing to remove a priori the short-term nontidal atmospheric and oceanic induced variations of the gravity potential via the socalled Atmosphere and Ocean De-aliasing Level-1B (AOD1B) products, their use for LAGEOS data processing would allow a direct comparison of results and a rigorous combination of the solutions. Since the consideration of short-term non-tidal atmospheric and oceanic mass redistributions by means of AOD1B time series reveals a significant impact on LAGEOS data processing results, the AOD1B time series has been consistently prolongated back to the advent of LAGEOS-1 in 1976. An analysis for the period 1993-2006 leads to the major findings that the consideration of atmospheric and oceanic mass redistributions result in a considerably reduced seasonal signal in the LAGEOS C20 time series. This in turn reduces the correlation to GRACE significantly by about 30%. This is in opposite to what one would expect, i.e., a better agreement between GRACE and LAGEOS if common standards are applied. Thus, a LAGEOS solution corrected for short-term non-tidal atmosphere and ocean effects is much less sensitive to primarily annual hydrological mass variations than GRACE. In addition, significant semi-annual signals remain. Other indicators such as the unresolved bias between LAGEOS and GRACE in the order of 2·10-10 or LAGEOS orbits and Satellite Laser Ranging (SLR) observation residuals are hardly affected by the AOD1B model.