GNSS Water Vapor Tomography

The spatial distribution of the atmospheric humidity is difficult to observe, especially for larger domains with dimensions of tens or hundreds of kilometers. The signals of satellite positioning systems like GPS or Galileo are modified by the atmospheric water vapor, and a combination of a large number of such signals provides an opportunity to observe the humidity distribution with high temporal resolution under all weather conditions. The positioning signals are collected by ground-based receiver networks and processed in a certain way in order to separate the humidity information. The information obtained in this way is a nonlocal path-integrated quantity, and tomographic techniques are required to obtain spatially and temporally resolved humidity fields. The whole processing chain from signal detection and signal processing to the final tomographic reconstruction of the atmospheric humidity distribution is presented.