Inclusion of Global Navigation Satellite System radio occultation data into Center for Weather Forecast and Climate Studies Local Ensemble Transform Kalman Filter (LETKF) using the Radio Occultation Processing Package as an observation operator

The Local Ensemble Transform Kalman Filter (LETKF) is a system for data assimilation in the testing phase at the Center for Weather Forecast and Climate Studies of the Brazilian Institute for Space Research (CPTEC/INPE). This system introduces significant advantages over the traditional variational methodology in the inclusion of new observation systems because determining the observation operator does not involve inverse problems. The refractivity profile from the Global Navigation Satellite System (GNSS) radio occultation (RO) technique is an example of an additional source of unconventional observation with promising results over regions with low data coverage. To assimilate RO profiles using the LETKF system at CPTEC/INPE, the Radio Occultation Processing Package (ROPP) from Radio Occultation Meteorology Satellite Applications Facilities/European Organization for the Exploration of Meteorological Satellites (ROM SAF/EUMETSAT) was used as an observation operator. The goal of this work was to investigate the impact on the Atmospheric General Circulation Model of the CPTEC using ROPP as an operator of the assimilation of RO data into the LETKF system. The results showed that positive impacts were obtained in several evaluated variables, including humidity, particularly over South America, where the model used by the CPTEC produces better results.