Variational Assimilation Of GPS Occultation Observation Technique

We are short of the knowledge about the variations and structure of eath's atmosphere because of the limited spatiotemporal resolution of routine sounding technique. GPS/LEO occultation technique supplies a new sounding way with global distribution, high precision, high vertical resolution, long-time stability, low cost and all weather. This technique will have a huge promotion on the probing of neutral atmosphere and ionosphere. Also, it is very important for the numerical weather prediction and the climate research.This thesis focuses on the retrieval algorithm of neutral atmosphere by GPS radio occultation and the application of the variational assimilation. Then discuss the technique using for the numerical weather prediction. The main work can be summarized as follow:1. Simply introduce the earth's atmosphere and radio occultation technique. Describe the significance, history and development of this technique, and values on the GPS meteorology using for defence construction and national economy.2. Discuss the radio occultation technique in details. Take the COSMIC (the Constellation Observing System for Meteorology, Ionosphere and Climate) project for example, introduce the occultation observation system (including the GPS and LEO satellites), the observation data processing (including data acquisition, accurate orbit determination, correction and retrieval processing ), also about the characteristics of occultation observation.3. Talk about the atmospheric refraction and the radio waves transmission in the neutral atmosphere. Then give the details about the standard retrieval algorithm of neutral atmosphere by GPS occultation, with the assumption of spherical symmetry. The retrieval technique about ionosphere are also discussed.4. Use the variational assimilation in order to resolve the problems in standard retrieval technique. Introduce the history and development of data assimilation, and different assimilation systems. For 1-Dimension VARiation, give two methods to resolve the minimum problem about cost function.: Newton-iteration and Levenberg-Marquardt way. Also discuss the defects and benefits using different assimilation parameters. Then introduce the 4-Dimension VARiation, which is popula(?)...