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Champ Climate Data Based on the Inversion of Monthly Average Bending Angles : Volume 7, Issue 12 (02/12/2014)

By Danzer, J.

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Book Id: WPLBN0003999541
Format Type: PDF Article :
File Size: Pages 9
Reproduction Date: 2015

Title: Champ Climate Data Based on the Inversion of Monthly Average Bending Angles : Volume 7, Issue 12 (02/12/2014)  
Author: Danzer, J.
Volume: Vol. 7, Issue 12
Language: English
Subject: Science, Atmospheric, Measurement
Collections: Periodicals: Journal and Magazine Collection (Contemporary), Copernicus GmbH
Historic
Publication Date:
2014
Publisher: Copernicus Gmbh, Göttingen, Germany
Member Page: Copernicus Publications

Citation

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Danzer, J., Gleisner, H., & Healy, S. B. (2014). Champ Climate Data Based on the Inversion of Monthly Average Bending Angles : Volume 7, Issue 12 (02/12/2014). Retrieved from http://www.ebooklibrary.org/


Description
Description: Wegener Center for Climate and Global Change (WEGC), University of Graz, Graz, Austria. Global Navigation Satellite System Radio Occultation (GNSS-RO) refractivity climatologies for the stratosphere can be obtained from the Abel inversion of monthly average bending-angle profiles. The averaging of large numbers of profiles suppresses random noise and this, in combination with simple exponential extrapolation above an altitude of 80 km, circumvents the need for a statistical optimization step in the processing. Using data from the US–Taiwanese COSMIC mission, which provides ~1500–2000 occultations per day, it has been shown that this average-profile inversion (API) technique provides a robust method for generating stratospheric refractivity climatologies.

Prior to the launch of COSMIC in mid-2006, the data records rely on data from the CHAMP (CHAllenging Mini-satellite Payload) mission. In order to exploit the full range of available RO data, the usage of CHAMP data is also required. CHAMP only provided ~200 profiles per day, and the measurements were noisier than COSMIC. As a consequence, the main research question in this study was to see if the average bending-angle approach is also applicable to CHAMP data.

Different methods for the suppression of random noise – statistical and through data quality prescreening – were tested. The API retrievals were compared with the more conventional approach of averaging individual refractivity profiles, produced with the implementation of statistical optimization used in the EUMETSAT (European Organisation for the Exploitation of Meteorological Satellites) Radio Occultation Meteorology Satellite Application Facility (ROM SAF) operational processing.

In this study it is demonstrated that the API retrieval technique works well for CHAMP data, enabling the generation of long-term stratospheric RO climate data records from August 2001 and onward. The resulting CHAMP refractivity climatologies are found to be practically identical to the standard retrieval at the DMI (Danish Meteorological Institute) below altitudes of 35 km. Between 35 and 50 km, the differences between the two retrieval methods started to increase, showing largest differences at high latitudes and high altitudes. Furthermore, in the winter hemisphere high-latitude region, the biases relative to ECMWF (European Centre for Medium-range Weather Forecasts) were generally smaller for the new approach than for the standard retrieval.


Summary
CHAMP climate data based on the inversion of monthly average bending angles

Excerpt
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