OVERVIEW OF ROSA RADIO OCCULTATION PROFILING CAPABILITIES ON-BOARD OCEANSAT-2

This contribution focuses on results obtained by processing, for the first time, ROSA Radio Occultation observations performed on-board the Indian mission OCEANSAT-2. It summarizes an in-depth quality check of ROSA data, performed during a Visiting Scientist activity funded by the ROM-SAF (Radio Occultation Meteorology – Satellite Application Facility) and in close cooperation with EUMETSAT and the Italian Space Agency. The focus here is on the potential use for operational weather forecasting. A set of ROSA raw data was processed using the EUMETSAT YAROS processor, a prototype created to develop new algorithms and to test them before introducing them into the operational chain. YAROS outputs are phases-amplitudes (at level 1a) and bending angles over impact parameter (at level 1b). Robust bias and standard deviation of bending angles against forward propagated ECMWF atmospheric data are used to evaluate the quality of the ROSA observations. Moreover, the ROM-SAF ROPP (Radio Occultation Processing Package) processor was also used for ROSA data processing. This second part focuses in addition on bending angles, refractivity and higher level products obtained from the YAROS level 1a input data. The validation was again based on ECMWF and also on co-located occultation profiles. The main issue affecting the ROSA data quality is tracking of the second GPS frequency L2. L2 data is often only acquired at altitudes above 20km, which makes the extrapolation of this data problematic. This currently severely limits the usefulness of the ROSA data (at least on OCEANSAT-2) and requires the development of more robust ionospheric correction algorithms and an investigation and possible mitigation of the problems onboard the satellite.