Evaluation and Assimilation of the COSMIC‐2 Radio Occultation Constellation Observed Atmospheric Refractivity in the WRF Data Assimilation System

This paper evaluates atmospheric refractivity observations from the COSMIC-2 (C2) radio occultation (RO) mission by comparing them with radiosonde (RS) observations, the European Center for Medium-Range Weather Forecasts (ECMWF) ERA5 reanalysis, and the National Centers for Environmental Prediction (NCEP) Global Forecast System (GFS) analysis for the period October 2019 to December 2020. C2 refractivity is overall in good agreement with the RS observations as well as the GFS and ERA5 analyses. The mean and standard deviations of the differences between C2 and RS, ERA5, and GFS refractivity are within ±0.3% and less than 2% respectively, with slightly higher differences (both systematic and random), in the lower levels of the troposphere.