Preprints
https://doi.org/10.5194/amt-2021-241
https://doi.org/10.5194/amt-2021-241

  25 Aug 2021

25 Aug 2021

Review status: this preprint is currently under review for the journal AMT.

An Assessment of Reprocessed GPS/MET Observations Spanning 1995–1997

Anthony James Mannucci1, Chi On Ao1, Byron A. Iijima1, Thomas K. Meehan1, Panagiotis Vergados1, E. Robert Kursinski2, Sean Healy3, Andras Horányi3, and William S. Schreiner4 Anthony James Mannucci et al.
  • 1Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, 91109, USA
  • 2PlanetiQ, Golden, CO, 80401, USA
  • 3European Centre for Medium-Range Weather Forecasts, Reading, RG2 9AX, United Kingdom
  • 4University Corporation for Atmospheric Research, Boulder, CO, 80307, USA

Abstract. We have performed an analysis of reprocessed GPS/MET data spanning 1995–1997 generated by CDAAC in 2007. CDAAC developed modified dual-frequency processing methods for the encrypted data (AS-on) during 1995–1997. We compared the CDAAC data set to the MERRA-2 reanalysis, separately for AS-on and AS-off, focusing on the altitude range 10–30 km. MERRA-2 did not assimilate GPS/MET data in the period 1995–1997. To gain insight into the CDAAC data set, we developed a single-frequency data set for GPS/MET, which is unaffected by the presence of encryption. We find excellent agreement between the more limited single frequency data set and the CDAAC data set: the bias between these two data sets is consistently less than 0.25 % in refractivity, whether or not AS is on. Given the different techniques applied between the CDAAC and JPL data sets, agreement suggests that the CDAAC AS-on processing and the single frequency processing are not biased in an aggregate sense greater than 0.25 % in refractivity, which corresponds approximately to a temperature bias less than 0.5 K. Since the profiles contained in the new single frequency data set are not a subset of the CDAAC profiles, the combination of the CDAAC data set, consisting of 9,579 profiles, and the new single-frequency data set, consisting of 4,729 profiles, yields a total number of 11,531 unique profiles from combining the JPL and CDAAC data sets. All numbers are after quality control has been applied by the respective processing activities.

Anthony James Mannucci et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on amt-2021-241', Anonymous Referee #1, 29 Oct 2021
  • RC2: 'Review of amt-2021-241', Anonymous Referee #2, 14 Nov 2021

Anthony James Mannucci et al.

Anthony James Mannucci et al.

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Short summary
The Global Positioning System (GPS) radio occultation (RO) technique is a satellite-based method for producing highly accurate vertical profiles of atmospheric temperature and pressure. RO profiles are used to monitor global climate trends, particularly in that region of the atmosphere that includes the lower stratosphere. Two data sets spanning 1995–1997 that were produced from the first RO satellite are highly accurate and can be used to assess global atmospheric models.