Retrieval of Tropospheric Refractivity Profiles Using Slant Tropospheric Delays Derived From a Single Ground-Based Global Navigation Satellite System Station

Abstract

The Global Navigation Satellite System (GNSS) has proved to be a powerful tool for applications in meteorology. In this study, we propose a novel slant tropospheric delay (STD) model to obtain the vertical distribution of atmospheric refractivity based on a single ground-based GNSS receiver. The new model is used to convert the STD into a function of the vertical gradient of temperature, and it is divided into two layers (above and below the tropopause) for integration. The optical vertical gradient of temperature can be estimated according to the STD obtained from the GNSS observations from a higher satellite elevation angle. The distribution of atmospheric refractivity can then be derived from the vertical gradient of temperature and the surface atmospheric refractivity. Moreover, to further improve the accuracy of the STD model-derived atmospheric refractivity, we correct it using a “theoretical retrieval” method based on the STDs obtained at a lower elevation angle. The optical ranges of theoretical retrieval are obtained above and below 5 km. Finally, a search is performed for the value of atmospheric refractivity that best fits the model equations, and this value is taken as the final inversion result. Data collected from eight GNSS stations and nearby radiosonde stations in 2016 were used to verify the new method. Using the radiosonde-derived values as a reference, the accuracy of the STD model-derived atmospheric refractivity was improved by 13.4% compared with the traditional technique. In addition, again using the radiosonde-derived values as a reference, the accuracy of the atmospheric refractivity derived with the optically corrected method was improved by 20.4% compared with the uncorrected STD model.