| Summary: | 碩士 === 國立成功大學 === 測量工程學系 === 88 === This research is a simulation study for the COSMIC project, which provides a simulated error analysis of the GPS occultation technique for the earth atmosphere temperature and pressure retrieval. The principle of the GPS occultation technique is to use the Doppler frequency shift, received by a low earth orbiting satellite, to profile the earth atmosphere temperature and pressure, for the application of weather prediction and weather and climate research. The error sources of the GPS occultation technique are complicated. However, knowing different effects of the error sources, we can evaluate the quality of the retrieved quantities.
The GPS/MET retrieval algorithms, the effects of the truncation error, orbit error of the GPS and COSMIC satellites, and observation error are discussed and summarized in this study. Experimental results indicate that various errors have little effects on atmosphere pressure retrieval. The effect of the truncation error on atmosphere temperature retrieval grows gradually with increasing altitude. The effect is less than 0.1K at troposphere, and the mean temperature error is ~1K at stratosphere. The maximum effect can reach ~3K at stratopause. The orbit error will not influence the retrieval if one-meter level accuracy orbit is available. The effect of the observation error on atmosphere temperature retrieval grows rapidly with increasing altitude. The effect is less than 0.1K at troposphere, and the mean temperature error is ~1K at stratosphere. The maximum effect can reach ~7K at stratopause.
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