Reply on RC1

Abstract

The Radio Occultations and Heavy Precipitation (ROHP) experiment aboard the Spanish PAZ satellite was deployed in 2018 with the objective of demonstrating the ability of Polarimetric Radio Occultation measurement (PRO) concept in detecting rain (liquid-phase precipitation). Analysis of these data since that time have also demonstrated the ability of PRO for detection of horizontally oriented frozen-phase precipitation. To verify these observations, a global climatological comparison is performed using the Cloudsat (94-GHz) radar as a reference, for different heights and taking into account the radio occultation (limb-based) viewing geometry. A robust relationship (e.g. high correlation coefficient) is found between the polarimetric radio occultation observable ΔΦ and the integrated ice water content along the rays for heights above the freezing level. The relationship is specially good over ocean, where the major precipitation features and the signatures of the Inter-Tropical Convergence Zone are well captured by the PAZ observations. Differences between over ocean and over land point towards different characteristics of the convective clouds above the freezing level, involving the orientation of frozen particles. The ratios between ΔΦ and along-ray integrated ice water content are further validated with single particle forward scattering simulations, and the results indicate that a combination of horizontally oriented aggregated ice particles and tilted pristine ice plates agree well with the observations. Overall, the global climatological results obtained in this study show the presence of horizontally oriented particles across the whole globe, and for a wide range of height layers. Furthermore, the relationship between ΔΦ and along-ray integrated ice water content can be used to attempt an inversion of the polarimetric radio occultation observations towards a potential retrieval of such water content.