Consistency and structural uncertainty of multi-mission GPS radio occultation records

Abstract

Abstract. Atmospheric climate monitoring requires observations of high quality that conform to the criteria of the Global Climate Observing System (GCOS). Radio occultation (RO) data based on Global Positioning System (GPS) signals are available since 2001 from several satellite missions with global coverage, high accuracy, and high vertical resolution in the troposphere and lower stratosphere. We assess the consistency and long-term stability of multi-satellite RO observations for use as climate data records. As a measure of long-term stability, we quantify the structural uncertainty of RO data products arising from different processing schemes. We analyze atmospheric variables from bending angle to temperature for four RO missions, CHAMP, Formosat-3/COSMIC, GRACE, and Metop, provided by five data centers. The comparisons are based on profile-to-profile differences aggregated to monthly medians. Structural uncertainty in trends is found to be lowest from 8 to 25 km of altitude globally for all inspected RO variables and missions. For temperature, it is < 0.05 K per decade in the global mean and < 0.1 K per decade at all latitudes. Above 25 km, the uncertainty increases for CHAMP, while data from the other missions – based on advanced receivers – are usable to higher altitudes for climate trend studies: dry temperature to 35 km, refractivity to 40 km, and bending angle to 50 km. Larger differences in RO data at high altitudes and latitudes are mainly due to different implementation choices in the retrievals. The intercomparison helped to further enhance the maturity of the RO record and confirms the climate quality of multi-satellite RO observations towards establishing a GCOS climate data record.

Initial Assessment of the COSMIC-2/FORMOSAT-7 Neutral Atmosphere Data Quality in NESDIS/STAR Using In Situ and Satellite Data

“…The data quality of these RO missions (except for COSMIC-2), including precision, stability, and structural uncertainty owing to inversion implementations, has been intensively validated in previous studies (i.e., [30][31][32]). All the RO data, including COSMIC-2 data, are downloaded from UCAR CDAAC (http://cosmic.cosmic.ucar.edu/cdaac/index.html).…”

“…The upper troposphere and lower stratosphere (UT/LS) is a critical region for understanding the radiative balance and climate processes. Studies have demonstrated that COSMIC temperature profiles in the lower stratosphere are very accurate (+/− 0.1K comparing with RS92 [46]) and stable (with a structural uncertainty of +/− 0.3 K in the trend [31]).…”

New insights into Rossby wave packet properties in the extratropical UTLS using GNSS radio occultations

“…6b). Recent studies using meridional winds and the Hilbert transform have shown the benefits of refining the methodology with semi-geostrophic coordinate adjustment Wirth, 2015, 2017) and even using wave activity flux (Takaya and Nakamura, 2001) for RWP diagnostics and optimizing the envelope's shape. Our approach to describe the phase and envelope propagation of an RWP in Fig.…”

Tropical cyclones vertical structure from GNSS radio occultation: an archive covering the period 2001–2018

“…With the advent of the RO, the scientific community was able to better understand the TC inner thermal structure and water vapour (WV) content at different layers. The TC track and intensity predictions, until 2006, were almost completely based on parameters such as surface temperature, cloud top temperature and surface winds at the outer radius (Brueske and Velden, 2003;Demuth et al, 2004;Dvorak, 1975;Kidder et al, 1978;Velden et al, 2006) from different remote sensing techniques such as infrared and microwave sounders and imagers (King et al, 1992), lidar (Poole et al, 2003), reflected light polarization (Knibbe et al, 2000), and oxygen A-band technique (Koelemeijer et al, 2002). Anthes et al (2003) were the first, comparing RO soundings with radiosonde observations during the Typhoon Toraji in 2001.…”