is a mission of opportunity: The Spanish Earth Observation PAZ satellite, ready for launch, was initially designed to carry a Synthetic Radar Aperture (SAR) as primary and sole payload. It included an advanced Global Navigation Satellite System (GNSS) receiver for precise orbit determination. The design of this particular GNSS receiver allows the tracking of 'occulting' signals, that is, signals transmitted by navigation satellites setting below the horizon of the Earth (or rising above it). The Spanish Ministry for Science and Innovation (MICINN) approved a proposal aimed to modify the original plans of PAZ, by including a polarimetric GNSS Radio-Occultation (RO) payload, the ROHP-PAZ experiment.
ROHP-PAZ is a proof-of-concept experiment: for the first time ever, GNSS RO measurements will be taken at two polarizations, to exploit the potential capabilities of polarimetric radio occultation for detecting and quantifying heavy precipitation events and other de-polarizing atmospheric effects (e.g. cloud ice). If the concept is proved, PAZ will mean a new application of the GNSS Radio-Occultation observations, by providing coincident thermodynamic and precipitation information with high vertical resolution within regions with thick clouds.
ROHP-PAZ potential impact: Coincident thermodynamic and precipitation information with high vertical resolution within regions with thick clouds might help understanding the thermodynamic conditions underlying intense precipitation, which is relevant because these events remain poorly predicted with the current climate and weather model parametrization. A better understanding of the thermodynamics of heavy precipitation events is necessary towards improving climate models and quantifying the impact of climate variability on precipitation. The particular advantage of GNSS polarimetric RO is that their signals are in the microwave spectrum which, unlike infrared sensing technology, is little influenced by clouds, not even by the thick clouds that are typically associated with heavy precipitation.
During 2016 the final results of the ground-based experiment have been published, together with a new approach to invert the observables. During this year, the team has also developed the algorithms which will be used in actual data to separate the hydrometeor component of the observables (of interest) from other undesired components (systematic effects).
Padullés, R., Cardellach, E., de la Torre Juárez, M., Tomas, S., Turk, F. J., Oliveras, S., Ao, C. O., Rius, A., Atmospheric polarimetric effects on GNSS Radio Occultations: the ROHP-PAZ field campaign,Atmospheric Chemistry and Physics, 16, pp. 635-649, 2016, jan, doi:10.5194/acp-16-635-2016
Padullés, R., Cardellach, E., Rius, A., Untangling rain structure from polarimetric GNSS Radio Occultation observables: a 2D tomographic approach, European Journal of Remote Sensing, 49, pp. 571-585, 2016, doi:10.5721/EuJRS20164930
Senior Institute's members involved
, S. Ribó, A. Rius