Monthly anomalies are derived by subtraction of a deterministic signal model (bias, trend, annual and semi-annual variations) from the monthly solutions. The signal model is fitted to the monthly means of all time-series in the time period 2004-2010, and extrapolated to earlier or later epochs to avoid poor quality solutions in the early or late phase of the GRACE mission to impact the signal model (each month is weighted equally).

For each spherical harmonic coefficient an individual model is fitted. For comparisons in the spherical harmonic domain no filter is applied. Low degree anomalies are dominated by residual signal content (non-seasonal hydrology), while the higher degree anomalies are dominated by noise.

The accuracy assessment (errors) of the combined solutions is derived empirically from the differences to the individual gontributions.

month	degree amplitudes of anomalies	degree amplitudes of errors
04/2002
05/2002
08/2002
09/2002
10/2002
11/2002
12/2002
01/2003
02/2003
03/2003
04/2003
05/2003
07/2003
08/2003
09/2003
10/2003
11/2003
12/2003
01/2004
02/2004
03/2004
04/2004
05/2004
06/2004
07/2004
08/2004
09/2004
10/2004
11/2004
12/2004
01/2005
02/2005
03/2005
04/2005
05/2005
06/2005
07/2005
08/2005
09/2005
10/2005
11/2005
12/2005
01/2006
02/2006
03/2006
04/2006
05/2006
06/2006
07/2006
08/2006
09/2006
10/2006
11/2006
12/2006
01/2007
02/2007
03/2007
04/2007
05/2007
06/2007
07/2007
08/2007
09/2007
10/2007
11/2007
12/2007
01/2008
02/2008
03/2008
04/2008
05/2008
06/2008
07/2008
08/2008
09/2008
10/2008
11/2008
12/2008
01/2009
02/2009
03/2009
04/2009
05/2009
06/2009
07/2009
08/2009
09/2009
10/2009
11/2009
12/2009
01/2010
02/2010
03/2010
04/2010
05/2010
06/2010
07/2010
08/2010
09/2010
10/2010
11/2010
12/2010
02/2011
03/2011
04/2011
05/2011
07/2011
08/2011
09/2011
10/2011
11/2011
12/2011
01/2012
02/2012
03/2012
04/2012
06/2012
07/2012
08/2012
09/2012
11/2012
12/2012
01/2013
02/2013
04/2013
05/2013
06/2013
07/2013
10/2013
11/2013
12/2013
01/2014
03/2014
04/2014
05/2014
06/2014
08/2014
09/2014
10/2014
11/2014
01/2015
02/2015
03/2015
04/2015
05/2015
07/2015
08/2015
09/2015
12/2015
01/2016
02/2016
03/2016
05/2016
06/2016
07/2016
08/2016
11/2016
12/2016
01/2017
03/2017
04/2017
05/2017
06/2017