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    New global GRACE gravity field model ITG-Grace2010New global GRACE gravity field model ITG-Grace2010  
 

 

New global GRACE gravity field model ITG-Grace2010

The new gravity field model ITG-Grace2010 has recently been released. It was calculated at Bonn University from 7 years of GRACE level 1B observations (2002-08 – 2009-08) and consists of three parts: daily solutions calculated using a Kalman smoother, unconstrained monthly solutions, and a high-resolution long-time mean.

 

Daily solutions

Daily gravity field snapshots have been derived using a Kalman smoother estimation procedure which takes into account prior information about spatial and temporal correlation patterns derived from geophysical models. For more information see Kurtenbach et al. 2009 and Hotstory Kalman.

 

Unconstrained monthly solutions

For each month of the observation period (2002-08 to 2009-08) a set of spherical harmonic coefficients for degrees n=1...120 was estimated without applying any regularization. In addition to the commonly used background models the daily Kalman solutions were used as improved de-aliasing product. A monthly mean of the daily solutions was restored afterwards. This lead to a significant increase in accuracy, especially in the smaller spatial scales as illustrated in the frequency domain in Fig. 2. Therefore, less filtering is necessary in post-processing as shown in Fig.1 where only a 300 km Gaussian filter was applied. Furthermore, the full variance-covariance matrix is provided for each monthly solution.

 

Monthly GRACE solution 2007-04 filtered with a Gaussian filter of 300km.
Degree variances of the ITG-Grace2010 monthly solutions (red) as differences compared to the static model. As a comparison, the differences for the GFZ-RL04 time series are plotted in blue, which represent the accuracy of pervious GRACE releases.

Static solution ITG-Grace2010s

A static gravity field model has been calculated as a long-term mean over the complete time span (2002-08 – 2009-08) complete up to degree a spherical harmonic degree of 180. Again the daily solutions were introduced as additional de-aliasing product. The full variance-covariance matrix is also provided for the static solution.

 

All parts of the gravity field model ITG-Grace2010 can be downloaded via the website.

 

References:

Kurtenbach , E. , Mayer-Gürr , T. , Eicker , A. : Deriving daily snapshots of the Earth's gravity field from GRACE L1B data using Kalman filtering, Geophys. Res. Lett., 36, 2009

 

Mayer-Gürr , T. , Kurtenbach , E. , Eicker , A. : ITG-Grace2010 gravity field model.

URL: www.igg.uni-bonn.de/apmg/index.php.