Preliminary analysis of error characteristics in atmospheric inversion of GPS radio occultation
大气掩星反演误差特性初步分析

GPS radio atmospheric occultation technique can measure the profiles of the global meteorological fields of the neutral atmosphere, from which we can obtain the atmosphere refractivity, pressure, density, temperature, and water vapor. The basic theory of the technique is the inversion method of Abel integration. Some factors such as the Earth's oblateness, the ionospheric dalay, the large-scale horizontal refractive index gradients in the atmosphere,and atmospheric multipath can influence the precision of retrieval. In this paper, we discuss the effect of the Earth's oblateness and ionosphere on the retrieval, and analyze the result of the local curvature correction and the ionosphere calibration. The excess phase delay is simulated by using the observed CHAMP orbit data, the ionospheric model and experiential atmospheric model, and the method of 3D-tracing technology. Inversion errors of the height from 0 to 60 km are obtained by comparison of the retrieval parameter profile and model profile, and studied by using statistical methods for several occultations. The result shows that local curvature calibration and ionosphere calibration are very important for GPS occultation inversion of high precision. Ionospheric residual influence is the main reason of restricting the retrieval precision from 30 km to 60 km, and it is necessary to develop new ionosphere calibration methods for atmosphere inversion of higher precision.