GNSS掩星中大气水汽的非线性反演

A non-linear inversion method for retrieval of water vapour from radio occultation measurements

研究利用无线电掩星探测数据反演大气水汽参数 .文中使用一维非线性方法 ,反演对流层水汽压廓线 .首先 ,定义了一维目标函数 ,并以几何光学假设为前提 ,反演出电波弯曲角 ;将电波弯曲角作为掩星探测量 ,大气模式输出的温、湿参量作为初始场 ,代入目标函数 ,对目标函数求最优反演出水汽压廓线 .文中给出了部分反演结果 ,经讨论分析认为 :非线性方法反演水汽压对初始场的精度依赖较小 ,能够同时反演出大气温度、水汽压廓线及相应的误差分布 ,对数值天气预报的应用及数据同化研究具有重要意义 .

A non-linear inversion method to retrieve water vapor profiles in the troposphere with radio occultation measurements is presented in this paper. We define a one-dimensional cost function, and retrieve bending angles by the approximation of geometric optics, with excess phase delay and orbit data of the GNSS and LEO satellites. And then the retrieved bending angle as a vector of occultation measurements, with priori state vectors composed of temperature and humidity from models are put into the cost function. The water vapor is retrieved with minimizing the cost function. By analysis of these retrieved profiles, it is suggested that the present method can simultaneously retrieve both temperature and water vapor profiles and the corresponding error covariance. This method is less sensitive to errors in the a priori state. These advantages would be favorable to the application of this method to assimilation in numerical forecasting models.