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https://doi.org/10.5194/amt-2018-29
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.
Research article
12 Feb 2018
Review status
This discussion paper is a preprint. It is a manuscript under review for the journal Atmospheric Measurement Techniques (AMT).
Comparison study of COSMIC RO dry air climatologies based on average profile inversion
Julia Danzer1,2, Marc Schwärz1,2, Veronika Proschek1,2, Ulrich Foelsche2,1, and Hans Gleisner3 1Wegener Center for Climate and Global Change (WEGC), University of Graz, Graz, Austria
2Institute for Geophysics, Astrophysics, and Meteorology/Institute of Physics (IGAM/IP), University of Graz, Graz, Austria
3Danish Meteorological Institute (DMI), Copenhagen, Denmark
Abstract. Recently a new approach for the production of GNSS radio occultation climatologies has been proposed. The idea is to perform the averaging of individual profiles already in bending angle space and propagating the mean bending angle profiles through the Abel transform. Climatological products of refractivity, density, pressure, and temperature are directly retrieved from the mean bending angles.

The averaging of a large number of profiles suppresses noise in the data, enabling observed bending angle data to be used up to 80 km without the need of a priori information. Above that altitude some background information for the Abel integral is still necessary.

This work is a follow up study, having the focus on the comparison of the average profile inversion climatologies (API) from the two processing centers WEGC and DMI, studying monthly COSMIC data from January to March 2011. The impact of different backgrounds above 80 km is tested, and different implementations of the Abel integral are investigated. Results are compared for the climatological products against ECMWF analysis, MIPAS, and SABER data.

It is shown that different implementations of the Abel integral have only little impact on the average profile inversion climatologies. On the other hand, different expansions of the bending angle profile above 80 km play a key role on the resulting monthly mean refractivities above 35 km altitude. Below that respective altitude the API climatologies show a good agreement between the two processing centers WEGC and DMI. Due to the downward propagation within the retrieval, effects of the upper initialization lead to differences in dry temperature climatologies already at 20 km altitude.

Applying at both centers an exponential extrapolation to the bending angles above 80 km, dry temperature climatologies agree between WEGC, DMI, ECMWF analysis, and MIPAS up to 35 km altitude within ± 0.5 K, and up to 40 km altitude within ± 1 K. We conclude that up to the lower stratosphere the average profile inversion is a valid – and in computation time much faster – alternative for the production of dry atmospheric RO climatologies.

Citation: Danzer, J., Schwärz, M., Proschek, V., Foelsche, U., and Gleisner, H.: Comparison study of COSMIC RO dry air climatologies based on average profile inversion, Atmos. Meas. Tech. Discuss., https://doi.org/10.5194/amt-2018-29, in review, 2018.
Julia Danzer et al.
Julia Danzer et al.
Julia Danzer et al.

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Short summary
Recently a new approach for the production of RO climatologies has been proposed. The idea is to propagate mean bending angle profiles through the processing and retrieve directly climatological products of refractivity, density, pressure, and temperature. The averaging suppresses noise in the data, allowing the bending angles to be used up to 80 km without the need of background information. This work has the focus on the comparison of the new climatologies between two processing centers.
Recently a new approach for the production of RO climatologies has been proposed. The idea is to...
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