Today atmospheric remote sensing of the neutral atmosphere with space geodetic techniques is an established field of research and applications. This is largely due to the technological advances and development of models and algorithms as well as, the availability of regional and global ground-based networks, and satellite-based missions. Water vapour is under sampled in current operational meteorological and climate observing systems. Advancements in Numerical Weather Prediction Models (NWP) to improve forecasting of extreme precipitation, requires GNSS troposphere products with a higher resolution in space and shorter delivery times than are currently in use. Homogeneously reprocessed GNSS observations on a regional and global scale have high potential for monitoring water vapour climatic trends and variability, and for assimilation into climate models. Unfortunately, these time series suffer from inhomogeneities (for example instrumental changes, changes in the station environment), which can affect the analysis of the long-term variability. NWP data have recently been used for deriving a new generation of mapping functions and in Real-Time GNSS processing these data can be employed to initialise Precise Point Positioning (PPP) processing algorithms, shortening convergence times and improving positioning. At the same time, GNSS-reflectometry is establishing itself as an alternative method for retrieving soil moisture.
We welcome, but not limit, contributions on the subjects below: Physical modelling of the neutral atmosphere using ground-based and radio-occultation data. Multi-GNSS and multi-instruments approaches to retrieve and inter-compare tropospheric parameters. Real-Time and reprocessed tropospheric products for forecasting, now-casting and climate monitoring applications. Assimilation of GNSS measurements in NWP and in climate models. Methods for homogenization of long-term GNSS tropospheric products. Studies on mitigating atmospheric effects in GNSS positioning and navigation, as well as observations at radio wavelengths. Usage of NWP data in PPP processing algorithms. Techniques on retrieval of soil moisture from GNSS observations and studies of ground-atmosphere boundary interactions.