Spatiotemporal Statistical Analysis of Slant Wet Delays From Ground-Based GNSS Stations Over China

Slant wet delays (SWDs) are delays of radio wave signals caused by water vapor in the neutral atmosphere along the signal paths. Their direct analysis provides statistical information that cannot be derived through the traditional precipitable water modeling, which only gives information about the vertical atmospheric column. In this study, we modeled the SWDs correlation lengths in space and time relative to 32 global navigation satellite system (GNSS) stations well distributed over China for the whole year 2018, based on series expansions in space and time of these SWDs for each standalone GNSS station. We found that the correlation length in angular separation in the sky seen from the station ranges from 12° to 20° and that the temporal correlation length varies within 2–7 days, with a strong dependence on climate types over China. Specifically, for the correlation length in angular separation in the sky, the latitude, temperature, and precipitation for each GNSS station were found to be highly correlated, while the longitude, altitude of the station, and pressure were found to be highly correlated with the correlation length in time. To the best of our knowledge, it is the first statistical analysis of this kind of SWDs over a large range of GNSS stations.