LES2GNSS: Large Eddy Simulations to Model Turbulent Fluctuations in GNSS Wet Delay

• Applicants: Dr. Gael Kermarrec; Professor Dr.-Ing. Harald Schuh
• Subject Area: Geodesy, Photogrammetry, Remote Sensing, Geoinformatics, Cartography
• Term: since 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 547859686

Global warming is associated with extreme weather events such as droughts or intense precipitations. Their best possible forecasts for the coming minutes up to the next few hours (nowcasting) should provide early warning for the population and rely on spatially and temporally highly resolved observations, with a rapid update cycle. Zenith Wet Delay (ZWD) from the Global Navigation Satellite Systems (GNSS) is related to the integrated precipitable water vapor (WV) and can provide information about fast-changing processes in the atmosphere such as cloud formation and convective initiation. The fluctuations of ZWD are associated with turbulent processes occurring in the lower part of the atmospheric boundary layer. They play an important role in the redistribution of trace gases, aerosols, heat, and momentum. Enhancing the description of those fluctuations will provide more accurate turbulence parameterizations in numerical weather forecast models and, thus, more trustworthy nowcasts. Radiative Transfer Models, which simulate the radiative transfer interactions of light scattering and absorption through the atmosphere, will also benefit from an improved understanding of WV fluctuations by correcting airborne/satellite data and allowing retrieving atmospheric composition. The spectral content of ZWD should also provide new insights into non-Kolmogorov turbulence, which is still not fully understood. Not only will the knowledge of physical processes benefit from such investigations but also the stochastic modeling of GNSS or VLBI observations, known to be correlated due to atmospheric turbulence. The unique combination of Large Eddy Simulations (LES), accurately retrieved ZWD, and meteorological observations such as radio soundings from the FESSTVaL experiment in Germany can provide solid foundations for understanding WV fluctuations and the related energy structures. Through the rigorous development of new innovative statistical estimators and retrieval methodologies, the project "LES2GNSS: Large Eddy Simulations to model turbulent fluctuations in GNSS wet delay" will lay the groundwork for monitoring spatio-temporal WV fluctuations and validating a model for use in weather, climate, and air quality applications.

• DFG Programme: Research Grants
• Co-Investigator: Dr.-Ing. Zhiguo Deng