Validation of Cloud Profiling Radar (CPR) measurements from the EarthCARE mission using observations from the Multi-Parameter Phased Array Weather Radar (MP-PAWR)

This thesis analyses the reflectivity measurements acquired by the Cloud Profiling Radar (CPR) onboard the EarthCARE satellite, operated by the European Space Agency (ESA) in collaboration with the Japan Aerospace Exploration Agency (JAXA), and those provided by the Multi-Parameter Phased Array Weather Radar (MP-PAWR), located in the Osaka region, Japan. The main objective is to quantitatively evaluate the level of agreement between the two data sources, identifying the main sources of discrepancy due to instrumental, geometric, and physical factors, and to assess the ability of the phased array radar to accurately represent the vertical structure of clouds and precipitation compared to a spaceborne reference system. In the first phase, a detailed technical study of the operational characteristics of both radar systems was carried out, with particular attention to the minimum detectable sensitivity of the MP-PAWR. This analysis allowed determining the detectability threshold of reflectivity as a function of distance, atmospheric attenuation, and the receiver system specifications. In parallel, algorithms were developed for the visualization, processing, and comparison of EarthCARE and MP-PAWR radar data, including procedures to identify satellite overpasses above the ground-based radar scanning volume, determined through an accurate analysis of the ground track repeat cycle. To ensure geometric consistency between the two datasets, MP-PAWR data were transformed into the same reference system as the CPR, including correction for Earth's curvature. After verifying the spatio-temporal correspondence, the effective intersection volume was selected, and a direct comparison of reflectivity measurements was conducted. For validation purposes, a volumetric matching approach based on the method of Schwaller and Morris was implemented, taking into account both spatial proximity and the similarity of radar reflectivity values between points in the two datasets. The mean bias, Root Mean Square Error (RMSE), and Pearson correlation coefficient were calculated, accompanied by graphical representations including scatter plots and latitude–altitude cross-sections. Analysis of multiple case studies revealed that, despite spatial and temporal consistency between observations, the reflectivity measured by MP-PAWR differs significantly from that of the CPR. This discrepancy is partly attributable to the operating frequency difference between the two instruments: the CPR operates at 94 GHz (W-band), sensitive to ice particles and small droplets, while the MP-PAWR operates at 9.71 GHz (X-band), more suited to detecting larger hydrometeors. This spectral divergence induces variations in scattering response, amplified by non-Rayleigh scattering effects, signal attenuation, and the application of the Moving Target Indication (MTI) filter in the phased array system. Overall, the results indicate that the MP-PAWR cannot be considered a direct validation tool for EarthCARE CPR observations, due to the physical and operational differences between the two systems. However, this work highlights the importance of the phased array radar as an experimental platform for algorithm testing and the development of methodologies for comparing spaceborne and ground-based radar observations.