A Method to Sophisticate the Water Vapor Tomography Model by Combining the ECMWF Grid Data

  Objectives  GNSS tomography technique is one of the most important methods to obtain the three-dimensional water vapor information. However, due to lack of enough initial prior information in the process of building the tomography model, the design matrix of tomography model is unstable and the tomographic result is poor, which has become an urgent problem to be resolved.

  Methods  First of all, the grid data derived from European Center for Medium-Range Weather Forecasting (ECMWF) is used to calculate the initial value of water vapor density in every voxel of interest area. And then, sophisticating the traditional tomography modeling using the calculated initial water vapor values. Finally, the influence of weightings of different equations in tomography model on tomographic result is also considered.

  Results  Comparing to the traditional methods, the proposed approach can enhance the accuracy of tomographic result by 41.2%, and its root mean squared error (RMSE) decreases from 1.82 g/m³ to 1.07 g/m³. Additionally, the mean absolute error (MAE), Bias and standard deviation (STD) also show a better performance than those of the traditional methods.

  Conclusions  The purpose is to improve the accuracy of tomographic water vapor profiles and used to sophisticate the established tomography model.