1. Institute of Geodesy and Geoinformation Science, Faculty VI Technische Universität Berlin Berlin Germany
2. German Research Centre for Geosciences GFZ Potsdam Germany
3. Cooperative Institute for Research in Environmental SciencesUniversity of Colorado Boulder Boulder CO USA
4. Earth System Research LaboratoryNOAA Boulder CO USA
5. Department of Mathematics University of Potsdam Potsdam Germany