Analysis and validation of Challenging Minisatellite Payload (CHAMP) radio occultation data

Abstract

We performed statistical comparisons of data from Challenging Minisatellite Payload (CHAMP) with European Centre for Medium‐Range Weather Forecasting (ECMWF) analyses. Our data processing technique includes: (1) radio holographic (radio optics) and canonical transform analysis of wave fields, (2) visualization of the local spatial spectra of wave fields for interactive data quality control, (3) ionospheric correction and noise reduction based on statistical optimization, (4) Abel inversion, and (5) comparison of CHAMP and ECMWF data based on forward modeling and inversion of artificial radio occultation data. In the tropics and midlatitudes at heights below 10 km, the CHAMP‐ECMWF differences are significantly greater than the GPS Meteorology (GPS/MET)‐ECMWF differences. Because big systematic negative differences between observed and simulated refraction angles are also observed in this region, we can explain that by poor quality of the CHAMP data in multipath regions due to signal tracking errors. Elsewhere, systematic CHAMP‐ECMWF differences do not exceed 1 K in the tropics and polar latitudes, and 0.5 K in midlatitudes, and deviations of CHAMP data from ECMWF analyses are smaller than those of GPS/MET data. This can be explained by enhancement in the latest ECMWF analyses.