Observing upper troposphere–lower stratosphere climate with radio occultation data from the CHAMP satellite

Foelsche, Ulrich; Borsche, Michael; Steiner, Andrea; Gobiet, Andreas; Pirscher, B.; Kirchengast, Gottfried; Wickert, Jens; Schmidt, T.

doi:10.1007/s00382-007-0337-7

Cited by 113 publications

(143 citation statements)

References 52 publications

Supporting

Mentioning

141

Contrasting

Order By: Relevance

“…Previous studies have reported the oscillatory vertical structure over the Antarctica in the ECMWF temperature (e.g., Randel et al, 2004;Uppala et al, 2005;Manney et al, 2005). RO-derived temperature also captured similar features (e.g., Gobiet et al, 2005;Foelsche et al, 2008). Although both the phase measurement and the derived RO temperature are able to detect the oscillations, the important distinction between them is that the phase path offers a higher level of transparency when the focus is on identifying NWP errors.…”

Section: Resultsmentioning

confidence: 70%

A perspective on the fundamental quality of GPS radio occultation data

Wee

Kuo

2015

Atmos. Meas. Tech.

View full text Add to dashboard Cite

Abstract. Radio occultation (RO) is a promising source of observation for weather and climate applications. However, the uncertainties arising from imperfect retrieval algorithms may weaken the overall confidence in the data and discourage their use. As an alternative approach of assessing the quality of RO data while avoiding the nuisance of retrieval errors, this study proposes to use minimally processed data (measurement) instead of derived RO data. This study compares measured phase paths with their model counterparts, simulated with an effective ray tracer for which the refractive indices along the complete ray path linking the transmitter and the receiver are realistically specified. The comparison of phase measurements with the European Centre for Medium-Range Weather Forecasts (ECMWF) data made in the observation space shows that the RO measurements are of sufficient accuracy to uncover regional-scale systematic errors in ECMWF's operational analysis and the 45-year reanalysis (ERA40), and to clearly depict the error growth of short-term ERA40 forecasts. In the southern hemispheric stratosphere, in particular, the RO measurements served as a robust reference against which both of the two analyses were significantly biased in opposite directions even though they were produced by the same center using virtually the same set of data. The measurement and ECMWF analyses showed a close agreement in the standard deviation except for the regions and heights that the quality of the ECMWF data is controversial. This confirms the high precision of RO measurements and also indicates that the main problem of the ECMWF analyses lies in their systematic error.

show abstract

Section: Resultsmentioning

confidence: 70%

A perspective on the fundamental quality of GPS radio occultation data

Wee

Kuo

2015

Atmos. Meas. Tech.

View full text Add to dashboard Cite

show abstract

“…Our experience of building atmospheric climatologies utilizing RO data (e.g., Foelsche et al, 2008;Scherllin-Pirscher et al, 2011a) showed that 10 • zonal bands were a reasonable choice for calculating mean atmospheric profiles from RO data. These bands range from 90 • S to 90 • N, resulting in 18 zonal bands.…”

Section: Average Over High-quality Profilesmentioning

confidence: 99%

“…Finally, errors in BAROCLIM are caused by discrete sampling times and locations of RO measurements (sampling error; see, e.g., Foelsche et al, 2008;Scherllin-Pirscher et al, 2011a). The sampling error depends on the number of profiles and atmospheric variability and can be estimated from reference data that reflect true spatial and temporal variability.…”

Section: Error Sourcesmentioning

confidence: 99%

Generation of a bending angle radio occultation climatology (BAROCLIM) and its use in radio occultation retrievals

et al. 2015

View full text Add to dashboard Cite

Abstract. In this paper, we introduce a bending angle radio occultation climatology (BAROCLIM) based on Formosat-3/COSMIC (F3C) data. This climatology represents the monthly-mean atmospheric state from 2006 to 2012. Bending angles from radio occultation (RO) measurements are obtained from the accumulation of the change in the raypath direction of Global Positioning System (GPS) signals. Best quality of these near-vertical profiles is found from the middle troposphere up to the mesosphere. Beside RO bending angles we also use data from the Mass Spectrometer and Incoherent Scatter Radar (MSIS) model (modified for RO purposes) to expand BAROCLIM in a spectral model, which (theoretically) reaches from the surface up to infinity. Due to the very high quality of BAROCLIM up to the mesosphere, it can be used to detect deficiencies in current state-of-the-art analysis and reanalysis products from numerical weather prediction (NWP) centers. For bending angles derived from European Centre for Medium-Range Weather Forecasts (ECMWF) analysis fields from 2006 to 2012, e.g., we find a positive bias of 0.5 to 1 % at 40 km, which increases to more than 2 % at 50 km. BAROCLIM can also be used as a priori information in RO profile retrievals. In contrast to other a priori information (i.e., MSIS) we find that the use of BAROCLIM better preserves the mean of raw RO measurements. Global statistics of statistically optimized bending angle and refractivity profiles also confirm that BARO-CLIM outperforms MSIS. These results clearly demonstrate the utility of BAROCLIM.

show abstract

“…Due to their high accuracy, RO data have significantly reduced systematic errors in global weather analyses (e.g., Healy and Thépaut, 2006;Cardinali, 2009) and their potential for 5 climate monitoring has been demonstrated with simulations studies (e.g., Leroy et al, 2006;Ringer and Healy, 2008;Foelsche et al, 2008b) and analyses (e.g., Foelsche et al, 2008aFoelsche et al, , 2009Ho et al, 2012;Steiner et al, 2013).…”

Section: Introductionmentioning

confidence: 99%

Comparison study of COSMIC RO dry air climatologies based on average profile inversion

Danzer¹,

Schwärz²,

Proschek³

et al. 2018

Preprint

Self Cite

View full text Add to dashboard Cite

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. 5The 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 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 20 much faster -alternative for the production of dry atmospheric RO climatologies.

show abstract

Observing upper troposphere–lower stratosphere climate with radio occultation data from the CHAMP satellite

Cited by 113 publications

References 52 publications

A perspective on the fundamental quality of GPS radio occultation data

A perspective on the fundamental quality of GPS radio occultation data

Generation of a bending angle radio occultation climatology (BAROCLIM) and its use in radio occultation retrievals

Comparison study of COSMIC RO dry air climatologies based on average profile inversion

Contact Info

Product

Resources

About