Topographic evaluation of fifth-generation GOCE gravity field models – globally and regionally

ESA (European Space Agency) has released a series of new-generation Earth gravity field models computed from gradiometry and GPS observations carried out aboard the GOCE (Gravity field and Ocean Circulation Explorer) satellite. In order to assess the quality of the new GOCE gravity fields, the sensitivity of satellite gravimetry to the gravitational attraction of the topographic masses can be exploited. This study uses topographic mass models to evaluate five generations of GOCE gravity models, both globally and regionally. As model representing Earth’s topography, ice-sheet and waterbody masses we use the new RET2014 rock-equivalent topography model by Curtin University (Perth). The gravitational potential of the RET2014 model is computed in spherical harmonics and in ellipsoidal approximation (ellipsoidal topographic potential, cf. Claessens and Hirt 2013, JGR Solid Earth, 118, 5991). We compare gravity from GOCE and from the RET2014 topography, whereby similar signal characteristics are taken as a sign of quality for the GOCE gravity fields. Our topographic evaluation shows a steadily improved agreement of the five model generations with topographyimplied gravity, and increase in GOCE model resolution. For the fifth-generation GOCE gravity fields, full resolution is indicated to harmonic degree ~220 (90 km scales), and partially resolved gravity features are found to degree ~270 (time-wise approach, TIM) and degree ~290-300 (direct approach, DIR), As such, the 5-generation GOCE models capture parts of the gravity field signal down to ~70 km spatial scales. This is a very significant improvement in satellite-only static gravity field knowledge compared to the pre-GOCE-era. Our comparisons show that models from the DIR approach improved relative to those from the TIM approach from the 2 to the 5 generation, with DIR offering the best short-scale performance (from degree 240 and beyond). Considering the unprecedented gravity field resolution achieved, the GOCE gravity field mission performed beyond the expectations. The GOCE gravity fields will serve as a de-facto-standard in a range of applications encompassing geodesy, geophysics and oceanography.

[1]  Sten Claessens.  Solutions to ellipsoidal boundary value problems for gravity field modelling , 2006 .

[2]  Grzegorz Michalak,et al.  GFZ GRACE Level-2 Processing Standards Document for Level-2 Product Release 0005 , 2012 .

[3]  Andrew Jarvis,et al.  Hole-filled SRTM for the globe Version 4 , 2008 .

[4]  B. Tapley,et al.  The Grace Mission: Status And Future Plans , 2001 .

[5]  Mark van der Meijde,et al.  GOCE data, models, and applications: A review , 2015, Int. J. Appl. Earth Obs. Geoinformation.

[6]  Thomas Gruber,et al.  Evaluation of the first GOCE static gravity field models using terrestrial gravity, vertical deflections and EGM2008 quasigeoid heights , 2011 .

[7]  C. Hirt.  GOCE's view below the ice of Antarctica: Satellite gravimetry confirms improvements in Bedmap2 bedrock knowledge , 2014 .

[8]  J. Janák,et al.  Comparison of Various Topographic-Isostatic Effects in Terms of Smoothing Gradiometric Observations , 2010 .

[9]  C. Voigt,et al.  VALIDATION OF GOCE GRAVITY FIELD MODELS BY ASTROGEODETIC VERTICAL DEFLECTIONS IN GERMANY , 2011 .

[10]  A. Konopliv,et al.  Venus Gravity: 180th Degree and Order Model , 1999 .

[11]  C. Amante,et al.  ETOPO1 arc-minute global relief model : procedures, data sources and analysis , 2009 .

[12]  Torsten Mayer-Gürr,et al.  EGM_TIM_RL05: An independent geoid with centimeter accuracy purely based on the GOCE mission , 2014 .

[13]  Rune Floberghagen,et al.  Upgrade of the GOCE Level 1b gradiometer processor , 2012 .

[14]  Eszter Szűcs.  Validation of GOCE time-wise gravity field models using GPS-levelling, gravity, vertical deflections and gravity gradient measurements in Hungary , 2012 .

[15]  C. Hirt,et al.  Ellipsoidal topographic potential: New solutions for spectral forward gravity modeling of topography with respect to a reference ellipsoid , 2013 .

[16]  C. Gerlach,et al.  Validation of GOCE global gravity field models using terrestrial gravity data in Norway , 2012 .

[17]  G. Masters,et al.  Update on CRUST1.0 - A 1-degree Global Model of Earth's Crust , 2013 .

[18]  Pieter Visser,et al.  Validation of GOCE gravity field models by means of orbit residuals and geoid comparisons , 2011 .

[19]  Ian M. Howat,et al.  A new bed elevation dataset for Greenland , 2012 .

[20]  Ahmed Abdalla,et al.  Validation of recent GOCE/GRACE geopotential models over Khartoum state - Sudan , 2012 .

[21]  M. Wieczorek,et al.  10.05 – Gravity and Topography of the Terrestrial Planets , 2007 .

[22]  Reiner Rummel,et al.  Comparisons of global topographic/isostatic models to the Earth's observed gravity field , 1988 .

[23]  D. Fabre,et al.  Global Bathymetry and Elevation Data at 30 Arc Seconds Resolution: SRTM30_PLUS , 2009 .

[24]  Torsten Mayer-Gürr,et al.  Gravity Field Recovery from GRACE-SST Data of Short Arcs , 2006 .

[25]  Bo Sun,et al.  Bedmap2: improved ice bed, surface and thickness datasets for Antarctica , 2012 .

[26]  H. Bock,et al.  GOCE: precise orbit determination for the entire mission , 2014, Journal of Geodesy.

[27]  Juraj Janák,et al.  Comparison and testing of GOCE global gravity models in Central Europe , 2011 .

[28]  R. Rummel,et al.  A Geodetic View on Isostatic Models , 2009 .

[29]  Bob E Schutz,et al.  Lageos Laser Ranging Contributions to Geodynamics, Geodesy, and Orbital Dynamics , 2013 .

[30]  F. Sansò,et al.  Global Moho from the combination of the CRUST2.0 model and GOCE data , 2013 .

[31]  Markus Rothacher,et al.  Observation of the Earth system from space , 2006 .

[32]  F. Sansò,et al.  First GOCE gravity field models derived by three different approaches , 2011 .

[33]  H. Moritz,et al.  Geodetic reference system 1980 , 1988 .

[34]  D. Tsoulis,et al.  An isostatically compensated gravity model using spherical layer distributions , 2004 .

[35]  M. Drinkwater,et al.  GOCE: ESA’s First Earth Explorer Core Mission , 2003 .

[36]  Jean-Charles Marty,et al.  ESA's satellite‐only gravity field model via the direct approach based on all GOCE data , 2014 .

[37]  N. K. Pavlis,et al.  Terrain-Related Gravimetric Quantities Computed for the Next EGM , 2006 .

[38]  N. G. Val’es,et al.  CNES/GRGS 10-day gravity field models (release 2) and their evaluation , 2010 .

[39]  N. K. Pavlis,et al.  The development and evaluation of the Earth Gravitational Model 2008 (EGM2008) , 2012 .

[40]  David E. Smith,et al.  GRGM900C: A degree 900 lunar gravity model from GRAIL primary and extended mission data , 2014, Geophysical research letters.

[41]  N. K. Pavlis,et al.  The development and evaluation of the Earth Gravitational Model 2008 ( EGM 2008 ) , 2012 .

[42]  D. Blitzkow,et al.  An evaluation of recent GOCE geopotential models in Brazil , 2012 .

[43]  B. Heck,et al.  Smoothing GOCE Gravity Gradients by Means of Topographic-Isostatic Reductions , 2011 .

[44]  Franz Barthelmes,et al.  Definition of Functionals of the Geopotential and Their Calculation from Spherical Harmonic Models , 2009 .

[45]  Carla Braitenberg,et al.  xploration of tectonic structures with GOCE in Africa and cross-continents arla , 2014 .

[46]  P. Novák,et al.  Gravitational Gradients at Satellite Altitudes in Global Geophysical Studies , 2013, Surveys in Geophysics.

[47]  Christian Hirt,et al.  Earth2014: 1 arc-min shape, topography, bedrock and ice-sheet models - Available as gridded data and degree-10, 800 spherical harmonics , 2015, Int. J. Appl. Earth Obs. Geoinformation.

[48]  Fernando Sansò,et al.  GOCE data analysis: the space-wise approach and the first space-wise gravity field model , 2010 .

[49]  M. Zuber,et al.  Mars high resolution gravity fields from MRO, Mars seasonal gravity, and other dynamical parameters , 2011 .

[50]  Thomas Gruber,et al.  Study of the Earth's short-scale gravity field using the ERTM2160 gravity model , 2014, Comput. Geosci..

[51]  M. Szelachowska,et al.  Accuracy assessment of GOCE-based geopotential models and their use for modelling the gravimetric quasigeoid - A case study for Poland , 2014 .

[52]  C. Gerlach,et al.  Comparison of GOCE Derived Satellite Global Gravity Models with EGM2008, the OCTAS Geoid and Terrestrial Gravity Data: Case Study for Norway , 2011 .

[53]  M. Wieczorek,et al.  Gravity and Topography of the Terrestrial Planets , 2015 .

[54]  R. Rummel,et al.  GOCE gravitational gradiometry , 2011 .

[55]  S. Claessens.  New relations among associated Legendre functions and spherical harmonics , 2005 .

[56]  Qile Zhao,et al.  Validation of static gravity field models using GRACE K-band ranging and GOCE gradiometry data , 2013 .

[57]  K. Ilk,et al.  Effects of topographic–isostatic masses on gravitational functionals at the Earth’s surface and at airborne and satellite altitudes , 2008 .

[58]  C. Hirt,et al.  Evaluation of the third- and fourth-generation GOCE Earth gravity field models with Australian terrestrial gravity data in spherical harmonics , 2014, Journal of Geodesy.

[59]  Kurt Seitz,et al.  A Wavelet-Based Assessment of Topographic-Isostatic Reductions for GOCE Gravity Gradients , 2014, Surveys in Geophysics.

[60]  W. Schuh,et al.  GOCE GRAVITY FIELD MODEL DERIVED FROM ORBIT AND GRADIOMETRY DATA APPLYING THE TIME-WISE METHOD , 2010 .

[61]  Christian Hirt.  RTM Gravity Forward-Modeling Using Topography/Bathymetry Data to Improve High-Degree Global Geopotential Models in the Coastal Zone , 2013 .