GPS Radio Occultation Technique And CHAMP Occultation Data Retrieval

Radio occultation technique can provide the Earth's ionospheric and neutral atmosphere with high accuracy, high vertical resolution and global coverage. It has advantages of all-weather capability, low expense, long-term stability etc. The first GPS/MET experiment Micro Lab1 demonstrated the potential of GPS radio occultation technique for a global monitoring Earth's atmosphere during the period of time from April 1995 to March 1997.This thesis focuses on some aspects of the radio occultation technique and its applications. The main works can be summarized as following:1. Introduce the international GPS radio occultation plans which have or will be carried out occultation research system and occultation data processing system in detail, that is going to promote occultation technique development in China.2. On the basis of the standard inverse algorithm for neutral atmospheric of GPS occultation data developed in JPL and GFZ, a computation process of neutral atmospheric retrieval was developed in SHAO. The retrieved atmospheric profiles from CHAMP data were compared with the ECMWF analysis data. This thesis presents the statistic and analysis results by the comparisons between these datasets, and discusses the data quality of CHAMP radio occultation data. The calculation results fairly approve the potential of GPS occultation data which might become an extremely valuable data source for the numerical weather prediction (NWP) and long-term monitoring of the Earth's climate.3. Based on one dimensional variational (1DVAR) retrieval technique, the refractivity or the bending angle profiles from GPS/LEO occultation is possibly used to be assimilated into NWP model, and then the atmospheric temperature and water vapor profiles, as well as the surface pressures are retrieved. Applying Levenberg-Marquardt algorithm associated with the background field from the ECMWF analyses we calculated some profile samples from CHAMP occultation refractivity observations. As a further discussion, the retrieved profiles are compared with the radiosonde data nearby the GPS/LEO occultation sounding...