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Article

Verification and Validation of the COSMIC-2 Excess Phase and Bending Angle Algorithms for Data Quality Assurance at STAR

1
CISESS, Earth System Science Interdisciplinary Center, University of Maryland, College Park, MD 20740, USA
2
Center for Satellite Applications & Research (STAR), NESDIS/NOAA, College Park, MD 20740, USA
*
Author to whom correspondence should be addressed.
Academic Editors: Xiaoming Wang, Suelynn Choy, Kefei Zhang, Karina Wilgan and Haobo Li
Remote Sens. 2022, 14(14), 3288; https://doi.org/10.3390/rs14143288
Received: 17 May 2022 / Revised: 24 June 2022 / Accepted: 5 July 2022 / Published: 8 July 2022
In recent years, Global Navigation Satellite System (GNSS) radio occultation (RO) has become a critical observation system for global operational numerical weather prediction. Constellation Observing System for Meteorology, Ionosphere, Climate (COSMIC) 2 (COSMIC-2) has been a backbone RO mission for NOAA. NOAA also began to purchase RO data from commercial sources in 2020. To ensure the consistent quality of RO data from different sources, NOAA Center for Satellite Applications and Research (STAR) has developed capabilities to process all available RO data from different missions. This paper describes the STAR RO processing systems which convert the pseudo-range and carrier phase observations to excess phases and bending angles (BAs). We compared our COSMIC-2 data products with those processed by the University Corporation for Atmospheric Research (UCAR) COSMIC Data Analysis and Archive Center (CDAAC). We processed more than twelve thousand COSMIC-2 occultation profiles. Our results show that the excess phase difference between UCAR and STAR is within a few centimeters at high altitudes, although the difference increases towards the lower atmosphere. The BA profiles derived from the excess phase are consistent with UCAR. The mean relative BA differences at impact height from 10 to 30 km are less than 0.1% for GLObal NAvigation Satellite System (GLONASS) L2C signals and Global Positioning System (GPS) L2C and L2P signals. The standard deviations are 1.15%, 1.15%, and 1.32% for GLONASS L2C signal and for GPS L2C and L2P signals, respectively. The BA profiles agree with those derived from European Center for Medium-range Weather Forecast (ECMWF) reanalysis version 5 (ERA5). The Signal-to-Noise-Ratio (SNR) plays an essential role in the processing. The STAR BA profiles with higher L1 SNRs (L1 at 80 km) tend to yield more consistent results than those from UCAR, with a negligible difference and a smaller deviation than lower SNR profiles. Profiles with lower SNR values tend to show a more significant standard deviation towards the surface during the open-loop stage in the lower troposphere than those of higher SNR. We also found that the different COSMIC-2 clock solutions could contribute to the significant relative BA difference at high altitudes; however, it has little effect on the lower troposphere comparisons given larger BA values. View Full-Text
Keywords: radio occultation; bending angle; excess phase; precise orbit determination; COSMIC-2 radio occultation; bending angle; excess phase; precise orbit determination; COSMIC-2
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MDPI and ACS Style

Zhang, B.; Ho, S.-p.; Cao, C.; Shao, X.; Dong, J.; Chen, Y. Verification and Validation of the COSMIC-2 Excess Phase and Bending Angle Algorithms for Data Quality Assurance at STAR. Remote Sens. 2022, 14, 3288. https://doi.org/10.3390/rs14143288

AMA Style

Zhang B, Ho S-p, Cao C, Shao X, Dong J, Chen Y. Verification and Validation of the COSMIC-2 Excess Phase and Bending Angle Algorithms for Data Quality Assurance at STAR. Remote Sensing. 2022; 14(14):3288. https://doi.org/10.3390/rs14143288

Chicago/Turabian Style

Zhang, Bin, Shu-peng Ho, Changyong Cao, Xi Shao, Jun Dong, and Yong Chen. 2022. "Verification and Validation of the COSMIC-2 Excess Phase and Bending Angle Algorithms for Data Quality Assurance at STAR" Remote Sensing 14, no. 14: 3288. https://doi.org/10.3390/rs14143288

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