New meteorological products based on Sentinel-1 and GNSS

Recently, the SAR Meteorology technique has demostrated the advantages of assimilating Sentinel-1 maps of Precipitable Water Vapor (PWV) in high resolution Numerical Weather Models (NWP) when forecasting extreme weather events [1]. The impact of Sentinel-1 information on NWP forecast depends on the acquisition parameters of Sentinel-1 images and the physical status of atmosphere [2]. Besides meteorological applications, enhancing NWP forecast could have an impact also on the mitigation of atmospheric artifacts in SAR interferometry applications based on NWP simulations [3].

This work describes a methodology to provide measurements of microwave propagation delay in troposphere. The proposed methodology is based on the processing of Sentinel-1 and GNSS data. In particular, Sentinel-1 images are processed by means of SAR Interferometry technique to get measurements of propagation delay in troposphere over land assuming that phase contribution due terrain displacements can be neglected. To fulfil this condition, the interferometric processing is carried out on Sentinel-1 images having the shortest temporal baseline of six days. Interferometric coherence is used to select portions of the interferogram where to estimates of PWV and the corresponding precision are provided. GNSS measurements of propagation delay in atmosphere are used to validate the Sentinel-1 measurements and derive a quality figure of PWV maps. A procedure is presented to concatenate PWV maps in time in order to derive a time series of spatially dense PWV measurements and the corresponding precisions.

Furthermore, Radio Occultation (RO) profiles are obtained by processing GNSS data. Profiles will be used to derive an estimate of propagation delay in troposphere over sea. In such a way, maps of propagation delay in atmosphere over both land and sea, even though characterized by a different spatial density of measurements, will be provided.

The study area includes the Basilicata, Calabria and Apulia regions and the Gulf of Taranto, southern Italy.

This work was supported by the Ministero dell'Istruzione, dell'Università e della Ricerca (MIUR), Italy, under the project OT4CLIMA.

References

[1] P. Mateus, J. Catalão, G. Nico, “Sentinel-1 interferometric SAR mapping of precipitable water vapor over a country-spanning area”, IEEE Transactions on Geoscience and Remote Sensing, 55(5), 2993-2999, 2017.

[2] P.M.A. Miranda, P. Mateus, G. Nico, J. Catalão, R. Tomé, M. Nogueira, “InSAR meteorology: High‐resolution geodetic data can increase atmospheric predictability”, Geophysical Research Letters, 46(5), 2949-2955, 2019.

[3] G. Nico, R. Tome, J. Catalao, P.M.A. Miranda, “On the use of the WRF model to mitigate tropospheric phase delay effects in SAR interferograms”, IEEE Transactions on Geoscience and Remote Sensing, 49(12), 4970-4976, 2011.