Comparisons of atmospheric mass variations derived from ECMWF reanalysis and operational fields, over 2003–2011

There are two spurious jumps in the atmospheric part of the Gravity Recovery and Climate Experiment-Atmosphere and Ocean De-aliasing level 1B (GRACE-AOD1B) products, which occurred in January-February of the years 2006 and 2010, as a result of the vertical level and horizontal resolution changes in the ECMWFop (European Centre for Medium-Range Weather Forecasts operational analysis). These jumps cause a systematic error in the estimation of mass changes from GRACE time-variable level 2 products, since GRACE-AOD1B mass variations are removed during the computation of GRACE level 2. In this short note, the potential impact of using an improved set of 6-hourly atmospheric de-aliasing products on the computations of linear trends as well as the amplitude of annual and semi-annual mass changes from GRACE is assessed. These improvements result from 1) employing a modified 3D integration approach (ITG3D), and 2) using long-term consistent atmospheric fields from the ECMWF reanalysis (ERA-Interim). The monthly averages of the new ITG3D-ERA-Interim de-aliasing products are then compared to the atmospheric part of GRACE-AOD1B, covering January 2003 to December 2010. These comparisons include the 33 world largest river basins along with Greenland and Antarctica ice sheets. The results indicate a considerable difference in total atmospheric mass derived from the two products over some of the mentioned regions. We suggest that future GRACE studies consider these through updating uncertainty budgets or by applying corrections to estimated trends and amplitudes/phases.

[1]  J. Kusche,et al.  Improving mass redistribution estimates by modeling ocean bottom pressure uncertainties , 2011 .

[2]  J. Kusche,et al.  Water mass variation in the Mediterranean and Black Seas , 2012 .

[3]  R. Steven Nerem,et al.  Preliminary observations of global ocean mass variations with GRACE , 2004 .

[4]  Hubert H. G. Savenije,et al.  The bias in GRACE estimates of continental water storage variations , 2006 .

[5]  Faisal Hossain,et al.  Inter-annual Water Storage Changes in Asia from GRACE Data , 2010 .

[6]  J. Famiglietti,et al.  Estimating groundwater storage changes in the Mississippi River basin (USA) using GRACE , 2007 .

[7]  M. Watkins,et al.  GRACE Measurements of Mass Variability in the Earth System , 2004, Science.

[8]  J. Wahr,et al.  Measurements of Time-Variable Gravity Show Mass Loss in Antarctica , 2006, Science.

[9]  J. Kusche,et al.  Comparisons of atmospheric data and reduction methods for the analysis of satellite gravimetry observations , 2013 .

[10]  W. Featherstone,et al.  Continental mass change from GRACE over 2002–2011 and its impact on sea level , 2012, Journal of Geodesy.

[11]  J. Thepaut,et al.  The ERA‐Interim reanalysis: configuration and performance of the data assimilation system , 2011 .

[12]  Rongjiang Wang,et al.  Gravity changes due to the Sumatra-Andaman and Nias earthquakes as detected by the GRACE satellites: a reexamination , 2010 .

[13]  E. Schrama,et al.  Present Day Regional Mass Loss of Greenland Observed with Satellite Gravimetry , 2011 .

[14]  Frank Flechtner,et al.  Simulating high‐frequency atmosphere‐ocean mass variability for dealiasing of satellite gravity observations: AOD1B RL05 , 2013 .

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

[16]  J. Kusche.  Approximate decorrelation and non-isotropic smoothing of time-variable GRACE-type gravity field models , 2007 .

[17]  Joseph L. Awange,et al.  Independent patterns of water mass anomalies over Australia from satellite data and models , 2012 .

[18]  Uncovered spurious jumps in the GRACE atmospheric de‐aliasing data: potential contamination of GRACE observed mass change , 2012 .

[19]  J. Famiglietti,et al.  Satellite-based estimates of groundwater depletion in India , 2009, Nature.

[20]  Hubert H. G. Savenije,et al.  The design of an optimal filter for monthly GRACE gravity models , 2008 .

[21]  S. Swenson,et al.  Post‐processing removal of correlated errors in GRACE data , 2006 .

[22]  C. Jekeli.  Alternative methods to smooth the Earth's gravity field , 1981 .

[23]  R. Preisendorfer,et al.  Principal Component Analysis in Meteorology and Oceanography , 1988 .

[24]  Jürgen Kusche,et al.  Mass distribution and mass transport in the Earth system , 2012 .

[25]  R. Forsberg,et al.  Variability of mass changes at basin scale for Greenland and Antarctica , 2012 .

[26]  J. Kusche,et al.  Separation of large scale water storage patterns over Iran using GRACE, altimetry and hydrological data , 2014 .

[27]  M. Watkins,et al.  The gravity recovery and climate experiment: Mission overview and early results , 2004 .

[28]  Victor Zlotnicki,et al.  Time‐variable gravity from GRACE: First results , 2004 .

[29]  J. Kusche,et al.  Land water contribution to sea level from GRACE and Jason-1measurements , 2013 .

[30]  Guillaume Ramillien,et al.  External geophysics, climate and environment Global land water storage change from GRACE over 2002-2009; Inference on sea level , 2010 .

[31]  Jürgen Kusche,et al.  Separation of global time-variable gravity signals into maximally independent components , 2012, Journal of Geodesy.

[32]  S. Swenson,et al.  Methods for inferring regional surface‐mass anomalies from Gravity Recovery and Climate Experiment (GRACE) measurements of time‐variable gravity , 2002 .

[33]  B. Scanlon,et al.  GRACE Hydrological estimates for small basins: Evaluating processing approaches on the High Plains Aquifer, USA , 2010 .

[34]  Karen E. Cady-Pereira,et al.  Uncertainties in atmospheric surface pressure fields from global analyses , 2008 .

[35]  F. Flechtner,et al.  Improved Non-tidal Atmospheric and Oceanic De-aliasing for GRACE and SLR Satellites , 2010 .

[36]  K. Neumayer,et al.  The New GFZ RL05 GRACE Gravity Field Model Time Series , 2012 .

[37]  W. Tad Pfeffer,et al.  Recent contributions of glaciers and ice caps to sea level rise , 2012, Nature.

[38]  F. Bryan,et al.  Time variability of the Earth's gravity field: Hydrological and oceanic effects and their possible detection using GRACE , 1998 .

[39]  B. Chao,et al.  Acceleration signal in GRACE time-variable gravity in relation to interannual hydrological changes , 2011 .

[40]  Harald Kunstmann,et al.  The Hydrological Cycle in Three State-of-the-Art Reanalyses: Intercomparison and Performance Analysis , 2012 .