The 17-year Radio Occultation Meteorology Satellite Application Facility (ROM SAF) Radio Occultation Climate Data Record

The Radio Occultation (RO) technique is based on measurements of phase shifts of GNSS radio waves onboard a low-Earth orbiting satellite. The processing of the measurements yields the refractive index of the Earth’s atmosphere, from which the temperature, pressure, and humidity fields can be retrieved. It is a limb-sounding technique, with a high vertical resolution, and with observational information retrieved from near-surface to the upper stratosphere. Numerous studies have demonstrated the accuracy of GNSS RO data, and their usefulness as a stable climate reference. Homogeneity of the data records are obtained by processing of the data using uniform processing software and a priori data throughout the length of the climate record.

We here present results from a validation of the 17-year ROM SAF RO Climate Data Record (CDR), based on processing of Metop, CHAMP, GRACE, and COSMIC data using excess-phase and amplitude data from EUMETSAT (the Metop mission) and UCAR (the CHAMP, GRACE, COSMIC, and Metop missions), and show examples of usage of the RO data, e.g., monitoring of the Quasi-Biennial Oscillation (QBO) and Sudden Stratospheric Warming (SSW) phenomena. We further discuss how RO measurements provide a direct means of measuring the geopotential heights of upper-troposphere and lower-stratosphere pressure surfaces and, hence, mean tropospheric temperatures.

The Radio Occultation Meteorology Satellite Application Facility (ROM SAF) is a decentralized operational processing facility under EUMETSAT. The main objective of the ROM SAF is to generate and deliver operational radio occultation products from GNSS RO instruments onboard Metop, Metop-SG, Jason-CS/Sentinel-6 and from other satellites for NWP and climate applications. The 17-year ROM SAF CDR is publically available from: http://www.romsaf.org. Further information about the ROM SAF products and services are available at the website.