Optimized smoothing of Gravity Recovery and Climate Experiment (GRACE) time‐variable gravity observations

[1] High-degree and high-order spherical harmonics of time-variable gravity fields observed by the Gravity Recovery and Climate Experiment (GRACE) gravity mission are dominated by noise. We develop two smoothing methods that suppress these high-degree and high-order errors with results superior to more commonly used Gaussian smoothing. These optimized smoothing methods considerably improve signal-to-noise levels of GRACE terrestrial water storage estimates relative to residual signal and noise over the oceans and show significantly better spatial resolution and lower leakage error. On the basis of analysis using an advanced land surface model, the equivalent spatial resolution from these optimized smoothing estimates is about 500 km, compared to the roughly 800–1000 km Gaussian smoothing that is required to suppress high-degree noise in the GRACE fields.

[1]  Clark R. Wilson,et al.  Simulated estimation of hydrological loads from GRACE , 2005 .

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

[3]  J. Famiglietti,et al.  Terrestrial water mass load changes from Gravity Recovery and Climate Experiment (GRACE) , 2006 .

[4]  J. D. Tarpley,et al.  Implementation of Noah land surface model advances in the National Centers for Environmental Prediction operational mesoscale Eta model , 2003 .

[5]  R. Nerem,et al.  Geophysical interpretation of observed geocenter variations , 1999 .

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

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

[8]  Jeffrey P. Walker,et al.  THE GLOBAL LAND DATA ASSIMILATION SYSTEM , 2004 .

[9]  Matthew Rodell,et al.  Spatial sensitivity of the Gravity Recovery and Climate Experiment (GRACE) time‐variable gravity observations , 2005 .

[10]  S. Seneviratne,et al.  Basin scale estimates of evapotranspiration using GRACE and other observations , 2004 .

[11]  Matthew Rodell,et al.  Low degree spherical harmonic influences on Gravity Recovery and Climate Experiment (GRACE) water storage estimates , 2005 .

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

[13]  C. Shum,et al.  Improved estimation of terrestrial water storage changes from GRACE , 2005 .

[14]  B. Tapley,et al.  Seasonal global mean sea level change from satellite altimeter, GRACE, and geophysical models , 2005 .

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

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

[17]  C. Shum,et al.  Non-isotropic filtering of GRACE temporal gravity for geophysical signal enhancement , 2005 .

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