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Inclusion of GNSS radio occultation data into CPTEC LETKF using ROPP as an observation operator


The Local Ensemble Transform Kalman Filter (LETKF) is a system for Data Assimilation (DA) 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 observations systems because determining the observation operator does not involve inverse problems. The refractivity profile from the GNSS (Global Navigation Satellite System) Radio Occultation technique is an example of an additional source of unconventional observation with promising results over regions with low data coverage. To assimilate Radio Occultation profiles using the LETKF system at CPTEC/INPE, the Radio Occultation Processing Package (ROPP) from ROM SAF/Eumetsat (Radio Occultation Meteorology Satellite Applications Facilities/European Organization for the Exploration of Meteorological Satellites) has been used as an observation operator. The goal of this work is to investigate the impact on the Atmospheric General Circulation Model of the CPTEC using ROPP as an operator of the assimilation of radio occultation 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 of the CPTEC presents better results. (AU)

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