Advances in the Use of Global Navigation Satellite System (GNSS) Polarimetric Radio Occultation (PRO) Measurements for NWP and Weather Applications

Conventional radio occultations (RO) are performed by tracking the phase delay induced in Global Navigation Satellite System (GNSS) signals as they propagate through the Earth’s atmosphere. Standard RO products such as bending angle profiles are routinely assimilated from the Constellation Observing System for Meteorology, Ionosphere and Climate (COSMIC-2) (Schreiner et. al., 2020) and commercially available RO into operational Numerical Weather Prediction (NWP) forecast models. The positive impact to forecasts of temperature, winds and precipitation when RO data are included in the model data assimilation (DA) system has been demonstrated (Ruston and Healy, 2021; Singh et. al., 2021, Prive et. al., 2022, Cucurull, 2023; IROWG, 2023).Polarimetric RO (PRO) enhances standard RO by receiving the GNSS signals with a dual-polarization RO receiver. The PRO concept has been flight-proven via the Radio Occultations and Heavy Precipitation (ROHP) experiment, operating onboard the Spanish PAZ satellite since May 2018 (Cardellach et. al., 2018). In addition to the capabilities of the conventional RO, PRO can provide an indication of precipitation at each vertical level, offering a potential to advance the assimilation of satellite data in precipitating conditions. Furthermore, these observations also provide unique diagnostics and observations for investigating the thermodynamic environment in and near convective precipitation (Neelin et. al., 2023), and assumptions underlying parameterizations used by operational NWP forecast models (Kidd et. al., 2013).This hybrid-format “2nd GNSS Polarimetric Radio Occultation workshop” follows on to the first (online-only) workshop from 2021. It represented a forum for addressing multiple uses and applications that have been studied in the nearly six years that PRO data have been available. The objectives of the workshop were threefold: (1) To provide potential users with an understanding of the PRO measurement concept, the available data, and the geophysical content within the PRO profile; (2) to provide data providers with a forum to better understand the requirements of scientific, NWP and climate model users, and (3) to connect these communities to develop new products and further the use of PRO in science and weather applications. Since many readers may be unfamiliar with the PRO concept, a brief description is provided, followed by summaries of presentations, discussion and ways forward on these three objectives is presented.