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. 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 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). 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. A three-step sequential quality control (QC) procedure is applied to both CDAAC and ROM data. CDAAC- and ROM-processed GRAS data from 2015 are compared here.
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.