基于层析和无线电掩星的电离层数据同化方法及建模研究

Ionospheric assimilation modeling has been playing an indispensable role in the quantitative and qualitative analysis of the dynamic process and characteristics of the ionosphere, which can effectively compensate for the shortage of traditional ground-based or satellite-based technique of ionospheric probing and can efficiently eliminate the deviation of theoretical or empirical models. It is of key importance in radio communication and satellite navigation to implement real-time monitoring and inversion of ionospheric TEC and electron density and thereafter building assimilation models. In the current study, the technique of data assimilation will be used to combine the physics-based models of the ionosphere with observations of ground-based GPS networks, ionosonde, and COSMIC data. First of all, the information of carrier phase and pseudo-range from the dual-frequency ground-based networks of GPS will be collected to calculate ionospheric TEC, and a regional GPS-based ionospheric TEC model will be developed accordingly. Secondly, the methodology of ionospheric tomography will be applied to reconstruct the profile of electron density from GPS signals. Thirdly, the radio occultation technique will be used to retrieve the ionospheric electron density along the tangent points during the occultation event when then GNSS receiver onboard COSMIC receive the GPS signals. Last but not least, with the Variational assimilation method and the Kalman filter technique being used, the processed data will be assimilated into a background empirical model (The IRI Model) and a theoretical model (The TIEGCM Model) respectively. Ultimately a data assimilation model of ionospheric TEC and electron density will be established to provide near real-time now-casting for the region of China and surrounding area.

电离层同化模型是对电离层结构和动力学过程进行定量分析和定性研究的重要方法，可以有效的弥补天基、地基观测数据的时空局限性以及经验模型和理论模型的精度偏差。对电离层电子密度和TEC进行实时监测、准确反演、同化建模是研究电离层对无线电通讯、卫星导航影响的关键问题。本项目将使用地基GPS台网、测高仪、COSMIC掩星等数据，针对我国及周边地区电离层区域变化特征进行数据同化建模研究。首先利用地基GPS台网进行区域TEC高精度解算并建立TEC区域模型；其次采用电离层层析方法对信号传播斜向TEC进行电子密度剖面反演；接着采用无线电掩星技术和COSMIC星座数据反演电子密度三维分布结构；最终依据上述解算和反演的TEC及电子密度，结合部分测高仪数据，分别选择IRI和TIEGCM作为电离层背景模型，采用变分法、Kalman滤波等手段进行数据同化方法研究，并针对中国及周边区域构建电离层三维电子密度和TEC模型。

电离层作为日地空间环境的关键一环，既是电磁波传播的物理载体，又是影响电波传输特性的重要媒介。电离层受到太阳辐射、地磁扰动、大气活动等多种空间环境因素作用，呈现出复杂的气候学和天气学变化特征，会对卫星导航、雷达成像、短波通信等涉及电波传播和电磁环境的技术手段产生严重影响。故而亟需开发高精度高分辨率的电离层模型，为电子装备、军事航天、空间环境现报预报等工程和科学应用提供及时、准确、有效的电离层误差修正信息。. 电离层数据同化是在基于物理机制的背景模型上，同化融合时空不规则分布的观测数据，使模型与数据相互匹配以达到更精确的现报预报结果。 数据同化是对电离层结构和动力学过程进行定量分析和定性研究的重要方法，可以有效的弥补天基、地基观测数据的时空局限性以及经验模型和理论模型的精度偏差。. 本研究利用中国及周边区域地基GNSS监测网络的TEC解算数据、COSMIC星座的天基掩星数据、地基测高仪等多源电离层数据，开发了基于三维变分和Gauss-Markov卡尔曼滤波算法的电离层同化现报预报方法。构建了中国及周边区域电离层高分辨率二维总电子含量和三维电子密度同化模型，开发了针对中国及周边区域的业务化电离层TEC和延迟修正服务产品。该模型可为卫星导航、雷达成像、短波通信等科学研究和工程应用提供相对及时、准确、有效的电离层TEC和误差修正信息，为电离层空间环境现报预报提供多维度、多参量的精确现报预报产品，能够有力保障我军民各项信息装备的效能发挥和安全运行，具有重要的科学意义和工程应用价值。