A study on the effects of heavy precipitation on Polarimetric Radio Occultation (PRO) bending angle observations
Presenter:
Kuo-Nung Wang
Jet Propulsion Laboratory
1. Jet Propulsion Laboratory, California Institute of Technology 2. Institut de Ciències de l’Espai, Insitut d’Estudis Espacials de Catalunya
Poster
Characterizing the near-surface moisture structure in extreme precipitation environments remains a challenging task with current remote sensing technology. To assimilate both moisture and precipitation information in the forecasting operation, the Spanish PAZ mission began the proof of concept experiment “Radio-Occultation and Heavy Precipitation with PAZ (ROHP-PAZ)” since February 2018. The on-board GPS-RO receiver used in this experiment is equipped with dual-orthogonal polarization capability to receive the signal in separate horizontal and vertical channels. The polarimetric phase difference observation between the two channels can be related to the asymmetric shape of the hydrometeors along the propagation path. This unique observation gives the Polarimetric RO (PRO) system the ability to detect and quantify heavy precipitation while simultaneously providing high vertical resolution moisture profiles that are retrievable from the standard GPS-RO measurements.
Up to now, the PRO concept has been studied using polarimetric phase shift assuming geometric optics propagation (e.g., analyzed through ray tracing techniques). It is known, however, that GPS-RO bending angle observations are more commonly used in data assimilation process. In addition, the propagation of the PRO signals is likely to suffer the multipath effect due to large moisture variance at lower troposphere, which is difficult to be simulated by classical ray tracing algorithms. In this research, we studied the polarimetric bending angle difference retrieved by the radio-holographic (RH) method to mitigate the multipath effect. The results are validated using the multiple phase screen (MPS) forward modeling method. The retrieval process is then applied to the cases from actual PAZ data collocated with Global Precipitation Measurement (GPM) Dual Polarization Radar (DPR) measurements and Integrated Multi-satellitE Retrievals for GPM (IMERG). We will present results for both, the individual and statistical comparison of polarimetric bending angle shifts in the PAZ instrument data, and discuss the strengths and limitations of this retrieval product.
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