开展GPS/LEO掩星低对流层大气反演关键技术研究，理论上和实践上改进目前低层大气GPS/LEO掩星反演算法,并在反演方法上有新的突破。低层大气GPS/LEO掩星反演精度主要受大气多路径、折射率水平分布不均匀和信噪比低等因素的影响。本项目结合全球大气分析场资料提供的折射率水平分布信息，开发新的中性大气掩星非球对称反演算法，降低折射率水平分布不均的影响；利用模拟仿真和COSMIC掩星资料，改进目前使用的无线电全息反演技术，最大程度地减少大气多路径的影响；建立识别折射率廓线中大气边界层顶高算法，并用于GPS/LEO掩星资料反演的质量控制，改善低对流层的反演精度。低层大气中包含了总水汽含量的绝大部分，它们的信息对于数值天气预报极为重要。GPS掩星低对流层大气反演精度的改进，可提高GPS/LEO掩星资料同化对全球数值天气预报的作用。

We will carry out a key technology research for GPS/LEO radio occultation inversion in the low troposphere, improve inversion algorithm in the theory and practice, and make a new breakthrough for radio occultation inversion method. The accuracy of GPS/LEO radio occultation inversion is mainly affected by atmospheric multi-path, horizontal gradient of refractive index, the lower signal to noise ratio, and other factors in the low troposphere. This project is to develop a new neutral atmosphere occultation inversion algorithm of non-spherically symmetry combined with the refractive index horizontal gradient information provided by the global atmospheric analysis field, to reduce the impact of the refractive index horizontal gradient; improve the radio holographic inversion technique using simulation and COSMIC radio occultation data to minimize the impact of atmospheric multi-path; to develop a new algorithm for automatic detection of the atmospheric boundary layer depth based on radio occultation refractive profile, which is used for the quality control of GPS/LEO radio occultation inversion to improve retrieval accuracy in the low troposphere. The most of the total water vapor content contained in the lower atmosphere is extremely important information for numerical weather prediction. GPS radio occultation retrieval accuracy improvements in the low troposphere can increase the assimilation of GPS/LEO occultation data the role of global numerical weather prediction.