Retrieval Analysis and Methodologies in Atmospheric Limb Sounding Using the GNSS Radio Occultation Technique PhD Defence by Stig Syndergaard

Content of presentation The GNSS radio occultation principle Data processing and exemplar results ----------------------------------------------- Violation of spherical symmetry assumption Severe weather gradients Earth’s oblateness Ionosphere calibration of data Conclusion and prospects

The GPS constellation 24 satellites Six 12 hour orbits Altitude: 20200 km Inclination: 55º Transmit dual frequency signals

Content of presentation The GNSS radio occultation principle Data processing and exemplar results ----------------------------------------------- Violation of spherical symmetry assumption Severe weather gradients Earth’s oblateness Ionosphere calibration of data Conclusion and prospects

Content of presentation The GNSS radio occultation principle Data processing and exemplar results ----------------------------------------------- Violation of spherical symmetry assumption Severe weather gradients Earth’s oblateness Ionosphere calibration of data Conclusion and prospects

Content of presentation The GNSS radio occultation principle Data processing and exemplar results ----------------------------------------------- Violation of spherical symmetry assumption Severe weather gradients Earth’s oblateness Ionosphere calibration of data Conclusion and prospects

Correcting for the Earth’s oblateness

Earth’s oblateness Before correction After correction

Content of presentation The GNSS radio occultation principle Data processing and exemplar results ----------------------------------------------- Violation of spherical symmetry assumption Severe weather gradients Earth’s oblateness Ionosphere calibration of data Conclusion and prospects

Model calculation of retrievals of the temperature in the case of a typical day-time, solar maximum ionosphere

GPS/MET occultation no. 259, day 35, 1997

Content of presentation The GNSS radio occultation principle Data processing and exemplar results ----------------------------------------------- Violation of spherical symmetry assumption Severe weather gradients Earth’s oblateness Ionosphere calibration of data Conclusion and prospects

14 days of GPS/MET occultations