Preliminary assessment of the scalability of GPS radio occultations impact in numerical weather prediction

Abstract

This work evaluates the scalability of the impact of the GPS radio occultation (GPSRO) measurements on the reduction of Numerical Weather Prediction forecast errors. We first show that the GPSRO bending angles from the eight satellites FORMOSAT‐3/COSMIC, CHAMP, and GRACE‐A lead to a reduction in geopotential height and temperature forecast Root Mean Square errors in Météo‐France global data assimilation system of a few percents in the Northern troposphere and larger in the Southern troposphere. As we double the number of GPSRO data assimilated, the forecast mean square error reduction grows by a factor between 1.1–1.8 for humidity and 1.3–2.4 for geopotential height, temperature, and wind. We do not observe any evidence of forecast impact saturation, though hints of leveling are apparent.