GNSS observations as a numerical weather prediction data source, first results for ZTD/IWV assimilation over Poland

Abstract:

The GNSS signal propagating from the satellite to the receiver is subjected to the phase delay due to the presence of the atmosphere. The signal’s troposphere phase delay is linked with the density of all gaseous constituencies, including one of the most important - water vapour. Current GNSS processing methodology does not provide a framework for effective estimation of line-of-sight troposphere delay between satellite and receiver because of that a new functional and stochastic modelling should be introduced. The project founded by National Science Foundation is looking to fill that gap by providing both: effective estimation procedure and assimilation methodology for line-of-sight GNSS observations.

This paper shows first results of the: validation and assimilation of GNSS data into NWP model. The investigated case studies cover severe weather events, such as : intensive storms, prolonged intensive rains, gusty winds. We applied the 3DVAR and 4DVAR assimilation schemes and used Integrated Water Vapour and Zenith Troposphere Delay from GNSS network in Poland

The results show impact of the newly introduced data on the location and intensity of the rain field the correction to the temperature and water vapour field is visible. Obtained data are validated against radiosonde profiles, automatic weather stations ground-based measurements and radar images.