Comparison of Daily GRACE Solutions to GPS Station Height Movements
In Kurtenbach (2011 ) and Kurtenbach et al. (2012 ) an approach has been introduced that allows to calculate daily gravity field solutions from GRACE data within the framework of a Kalman filter and smoother estimation. The method utilizes spatial and tem
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Comparison of Daily GRACE Solutions to GPS Station Height Movements Annette Eicker, Enrico Kurtenbach, Jürgen Kusche and Akbar Shabanloui
Abstract In Kurtenbach (2011) and Kurtenbach et al. (2012) an approach has been introduced that allows to calculate daily gravity field solutions from GRACE data within the framework of a Kalman filter and smoother estimation. The method utilizes spatial and temporal correlations of the expected gravity field signal derived from geophysical models in addition to the daily observations, thus effectively constraining the spatial and temporal evolution of the GRACE solution. Here, we offer an extended validation of these daily solutions by comparing the derived mass variations to vertical displacements at various permanent GPS stations. The comparison confirms the conclusion that the daily solutions contain significant high-frequent temporal gravity field information, especially in higher latitudes.
6.1 Introduction: The GRACE Kalman Filter Approach The standard analysis approach for GRACE data aims at the calculation of monthly (Watkins and Yuan 2007; Bettadpur 2007; Flechtner et al. 2010), 10-day (Bruinsma et al. 2010) or weekly (Flechtner et al. 2010) gravity field solutions. A temporal evolution of the mass variations, however, also occurs on much shorter time scales. It is therefore our goal to increase the temporal resolution of GRACE in order to determine these fast changes, which are for example present in atmospheric or barotropic A. Eicker (B) · E. Kurtenbach · J. Kusche · A. Shabanloui University of Bonn, Institute of Geodesy and Geoinformation, Nußallee 17, 53115 Bonn, Germany e-mail: [email protected] E. Kurtenbach e-mail: [email protected] J. Kusche e-mail: [email protected] A. Shabanloui e-mail: [email protected]
F. Flechtner et al. (eds.), Observation of the System Earth from Space - CHAMP, GRACE, GOCE and Future Missions, Advanced Technologies in Earth Sciences, DOI: 10.1007/978-3-642-32135-1_6, © Springer-Verlag Berlin Heidelberg 2014
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ocean variations. Since the data coverage provided by GRACE is not sufficient to allow for a recovery of gravity field snapshots on a day-to-day basis, the introduction of stochastic prior information from geophysical models as described in Kurtenbach et al. (2012) has to be used to stabilize the solutions. The Kalman filter combines this prior information and the daily GRACE observations in a joint estimation process and delivers an updated state of the gravity field for each day. Stochastic information is introduced in terms of the process model which formulates a prediction of the current state resulting from the state of the previous time step. The process model is constructed from spatial and temporal covariance matrices derived from the output of the geophysical models. The daily solutions described by the present paper are part of the GRACE gravity field model ITGGrace2010 (Mayer-Gürr et al. 2010) and can be downloaded at http://www.igg.unibonn.de/apmg/index.php?id=
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