Improved daily GRACE gravity field solutions using a Kalman smoother |
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| Institution: | 1. Space and Aviation Research Institute, King Abdulaziz City for Science and Technology (KACST), Riyadh, Saudi Arabia;2. Institute of Geodesy and Geoinformation (IGG), University of Bonn, Germany;3. National Research Institute of Astronomy and Geophysics (NRIAG), Helwan, Cairo, Egypt;1. State Key Laboratory of Geodesy and Earth''s Dynamics, Institute of Geodesy and Geophysics, Chinese Academy of Sciences, Wuhan, China;2. Institute of Earth Sciences, Academia Sinica, Taipei, Taiwan;3. Center for Space Research, University of Texas at Austin, Austin, USA;4. Department of Geological Sciences, Jackson School of Geosciences, University of Texas at Austin, Austin, USA;1. Department of Spatial Sciences, Curtin University, Perth, Australia;2. School of Geographical Sciences, University of Bristol, Bristol, UK;3. School of Earth and Ocean Sciences, Cardiff University, Cardiff, UK;4. Fenner School of Environment and Society, the Australian National University, Canberra, Australia |
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| Abstract: | Different GRACE data analysis centers provide temporal variations of the Earth's gravity field as monthly, 10-daily or weekly solutions. These temporal mean fields cannot model the variations occurring during the respective time span. The aim of our approach is to extract as much temporal information as possible out of the given GRACE data. Therefore the temporal resolution shall be increased with the goal to derive daily snapshots. Yet, such an increase in temporal resolution is accompanied by a loss of redundancy and therefore in a reduced accuracy if the daily solutions are calculated individually. The approach presented here therefore introduces 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. The GRACE data processing is then performed within the framework of a Kalman filter and smoother estimation procedure.The approach is at first investigated in a closed-loop simulation scenario and then applied to the original GRACE observations (level-1B data) to calculate daily solutions as part of the gravity field model ITG-Grace2010. Finally, the daily models are compared to vertical GPS station displacements and ocean bottom pressure observations.From these comparisons it can be concluded that particular in higher latitudes the daily solutions contain high-frequent temporal gravity field information and represent an improvement to existing geophysical models. |
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