ACP Atmospheric Chemistry and Physics ACP 1680-7324 Copernicus GmbH Göttingen, Germany 10.5194/acp-11-6687-2011 First results from the GPS atmosphere sounding experiment TOR aboard the TerraSAR-X satellite Beyerle G. 1 Grunwaldt L. 1 Heise S. 1 Köhler W. 1 König R. 1 Michalak G. 1 Rothacher M. 2 Schmidt T. 1 Wickert J. 1 Tapley B. D. 3 Giesinger B. 4 GFZ German Research Centre for Geosciences, Potsdam, Germany Swiss Federal Institute of Technology, Zurich, Switzerland Center for Space Research, University of Texas (UT-CSR), Austin, TX, USA Broad Reach Engineering, Tempe, AZ, USA 13 07 2011 11 13 6687 6699 This is an open-access article ditributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. This article is available from http://www.atmos-chem-phys.net/11/6687/2011/acp-11-6687-2011.html The full text article is available as a PDF file from http://www.atmos-chem-phys.net/11/6687/2011/acp-11-6687-2011.pdf

GPS radio occultation events observed between 24 July and 17 November 2008 by the IGOR occultation receiver aboard the TerraSAR-X satellite are processed and analyzed. The comparison of 15 327 refractivity profiles with collocated ECMWF data yield a mean bias between zero and −0.30 % at altitudes between 5 and 30 km. Standard deviations decrease from about 1.4 % at 5 km to about 0.6 % at 10 km altitude, however, increase significantly in the upper stratosphere. At low latitudes mean biases and standard deviations are larger, in particular in the lower troposphere. The results are consistent with 15 159 refractivity observations collected during the same time period by the BlackJack receiver aboard GRACE-A and processed by GFZ's operational processing system. The main difference between the two occultation instruments is the implementation of open-loop signal tracking in the IGOR (TerraSAR-X) receiver which improves the tropospheric penetration depth in terms of ray height by about 2 km compared to the conventional closed-loop data acquired by BlackJack (GRACE-A).

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