Abstract
Both the Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) Data Analysis and Archival Center (CDAAC) and the European Radio Occultation Meteorology Satellite Application Facility (ROM) process the radio occultation data from the Global Navigation Satellite System Receiver for Atmospheric Sounding (GRAS) onboard the MetOp-A/-B satellites. CDAAC- and ROM-processed GRAS data from 2015 are compared here. A three-step sequential quality control (QC) procedure is applied to both CDAAC and ROM data. Another QC check on the vertical sampling interval of the bending angle is applied to ROM data, which has a varying vertical sampling interval that is much higher than the CDAAC’s constant 20 m vertical sampling interval and causes a significant number of outliers below 10 km. The mean of the fractional difference in bending angle between CDAAC and ROM is reduced from ± 0.4 to ± 0.2%, and the standard deviation of the fractional difference in bending angle between CDAAC and ROM is reduced from 3 to 2% after QC in the upper troposphere and lower stratosphere (UTLS). The mean differences in temperature and specific humidity derived by CDAAC and ROM are within ± 0.4 K and ± 0.02 g kg−1 in the UTLS, respectively. The mean fractional difference in refractivity retrievals between CDAAC and ROM is on the order of 0.05% in the UTLS, and 2% below and 0.4% above it. There is a significant latitudinal dependence of the mean fractional difference in refractivity retrievals in the lower troposphere (below 400 hPa). The mean fractional difference is the largest near 850 hPa at the equator (about 2.7%).
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Acknowledgements
The author was supported by the National Key R&D Program of China (Grant 2018YFC1507302), and the Mathematical Theories and Methods of Data Assimilation supported by the National Science Foundation of China (Grant No. 91730304).
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Xu, X., Zou, X. Comparison of MetOp-A/-B GRAS radio occultation data processed by CDAAC and ROM. GPS Solut 24, 34 (2020). https://doi.org/10.1007/s10291-019-0949-5
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DOI: https://doi.org/10.1007/s10291-019-0949-5