The Polarimetric Radio Occultation (PRO) technique tracks GPS signals captured by Low-Earth-Orbit (LEO) satellites as they rise or set behind the Earth's limb. This method extends the capabilities of the traditional Radio Occultation (RO) approach by not only measuring the vertical profiles of thermodynamic variables but also incorporating polarimetric information. Unlike standard RO, PRO uses two orthogonal linear polarizations, horizontal (H) and vertical (V), offering relevant insights into atmospheric conditions.
Since its deployment aboard the PAZ satellite in 2018, the GNSS-PRO concept has been successfully demonstrated. In 2023, it was further implemented aboard three of Spire Global’s commercial CubeSats. The polarimetric capability of PRO allows it to retrieve the vertical profiles of differential phase shift (ΔΦ), the difference in phase delay between H and V polarizations. Heavy precipitation events, dominated by oblate spheroid-like hydrometeors, induce a positive differential phase shift as PRO signals traverse these conditions, enabling unique information into the microphysical properties of these precipitation events.
The primary hypothesis that PRO onboard PAZ is sensitive to oblate raindrops was validated; also, its response to frozen hydrometeors was unexpectedly demonstrated. The technique's performance was corroborated through comparisons with two-dimensional data like IMERG-GPM products and three-dimensional data from NEXRAD weather radars.
Ongoing analyses focus on evaluating the sensitivity of the Polarimetric Radio Occultation (PRO) technique to various microphysical parameterizations derived from the Weather Research and Forecasting (WRF) model and particle habits simulated using the Atmospheric Radiative Transfer Simulator (ARTS). This research is particularly centered on Atmospheric Rivers, aiming to examine how variations in microphysical parameterizations influence the PRO technique's ability to detect and characterize hydrometeors. These findings will contribute to a more comprehensive understanding of the phenomena associated with extreme weather systems, ultimately advancing the application of PRO in atmospheric science.
