Use of Global Positioning Satellites (GPS) Occultation Data in Numerical Weather Prediction

为了将传统数据稀疏的公海遥感大气数据正确纳入数值预测模型中，人们做出了广泛的努力。 沿着这条线，PI寻求通过改进旧方法以及探索新方法来推进全球定位卫星（GPS）掩星数据的同化。 GPS发射的无线电信号的折射程度取决于信号传播的大气的特性，因此可以用来获取大气热力学状态的知识。 该研究项目分为四个领域：1）提高PI在先前研究中使用的射线追踪方法（一种将弯曲角度剖面与观测剖面相匹配的正向建模计算）的计算效率，并提高其在对流层低层的性能； 2）开发一种高效的折射率同化方法，通过估计沿射线路径的平均大气折射率信息，获得折射率的综合效果； 3) 评估和量化 GPS 得出的屈光度数据中的误差； 4) 使用 GPS 数据检索的信息评估和检查现有的物理参数化方案。 考虑到 GPS 数据在未来可能发挥的作用，这项研究对天气预报的潜在影响是重大的。

Extensive efforts have been made to properly incorporate remotely sensed atmospheric data from open oceans where conventional data are sparse into the numerical prediction models. Along this line, the PI seeks to advance the assimilation of the Global Positioning Satellites (GPS) occultation data by improving old approaches as well as exploring a new method. The degree of refraction of the radio signals transmitted by the GPS depends on the properties of the atmosphere through which the signals travel, and thus can be used to gain the knowledge of the atmospheric thermodynamic state. This research project is divided into four areas: 1) Improve the computational efficiency of the raytracing approach (a forward modeling calculation to match the bending angle profile with the observed profile) used by the PI in her previous study and improve its performance in the lower troposphere; 2) Develop an efficient refractivity assimilation method by estimating the averaged atmospheric refractivity information along the ray path to obtain the integrated effect of refractivity index; 3) Assess and quantify errors in the GPS-derived refractivity data; 4) Evaluate and examine existing physical parameterization schemes using the information retrieved by the GPS data. The potential impact of this study on weather predictions is significant considering the role that GPS data likely will play in the future.