Although developed for positioning, Global Navigation Satellites Systems (GNSS) can be also exploited for troposphere sounding.
When a positioning accuracy below a centimeter level is requested, delays affecting GNSS signals in the tropospheric layer have to be properly accounted for. More specifically, the component of such delays due to the troposphere water vapor content, hardly to be modeled for the high temporal and spatial variability, have to be estimated in the adjustment of GNSS observations.
This is done in terms of time and station dependent ‘ancillary parameters’ called Zenith Wet Delays (ZWDs).
Since many years, the meteorological community has started to consider these by-product of high accuracy positioning as ‘observations’ of water vapor and to assimilate them in Numerical Weather Prediction models in some cases in a routinely way.
Moreover, a mixed community of meteorologist and GNSS experts has been exploring a dedicated use of GNSS for meteorological purposes, by designing and implementing ad hoc experimental networks .
Reaserches on this topic have been conducted within the geodesy and geomatic group since almost a decade, starting within an ESA funded project called METAWAVE.
Currently GEOlab is mainly working on the spatio-temporal stochastic characterization of GNSS water vapor delays derived from dense networks of permanent stations.
Basili P, Bonafoni S, Mattioli V, Pelliccia F, Ciotti P, Carlesimo G, Pierdicca N, Venuti G, Mazzoni A( 2010) Neural-network retrieval of integrated precipitable water vapor over land from satellite microwave radiometer. Microrad10, 11th Specialist Meeting on Microwave Radiometry and Remote Sensing of the Environment, 1-4 March 2010 Washington, DC, USA
Perissin D, Rocca F, Pierdicca N, Pichelli E, Cimini D, Venuti G, Rommen B (2011) Mitigation of atmospheric delay in INSAR: the ESA METAWAVE project, 2011 IEEE International Geoscience And Remote Sensing Symposium (IGARSS). Book Series: IEEE International Symposium on Geoscience and Remote Sensing IGARSS, pp. 2558-2561
Pierdicca N, Rocca F, Basili P, Bonafoni S, Carlesimo G, Cimini D, Ciotti P, Ferretti R, Marzano FS, Mattioli V, Montopoli M, Notarpietro R, Perissin D, Pichelli E, Rommen B, Venuti G (2011) Synergic use of EO, NWM and ground based measurements for mitigation of vapour artefacts in SAR interferometry, 2011 IEEE International Geoscience And Remote Sensing Symposium (IGARSS), Book Series: IEEE International Symposium on Geoscience and Remote Sensing IGARSS, pp. 2566-2569
Notarpietro R., Cucca M., Gabella M., G. Venuti, Perona G. (2011) Tomographic reconstruction of wet and total refractivity fields from GNSS receiver networks. Advances in space research, Volume 47, Issue 5, 1 March 2011, Elsevier, pp. 898-912.