1,1,3,4- 1National Research Council of Italy—Institute of Atmospheric Sciences and Climate (CNR-ISAC), National Research Council of Italy—Institute of Atmospheric Sciences and Climate (CNR-ISAC), Rome (RM), Italy (s.federico@isac.cnr.it)
- 2Geomatics Research & Development srl (GReD), via Cavour 2, 22074 Lomazzo, Italy
- 3Politecnico di Milano, DICA, Milano, Italy
- 4University of Rome “La Sapienza” - Faculty of Civil and Industrial Engineering, via Eudossiana, 18 - 00184 Rome - Italy
The ICREN and NEW-ARGENT projects aim at studying the impact of GNSS data assimilation on the precipitation forecast over Italy. Specifically, the assimilation of GNSS-ZTD together with lightning was studied in the ICREN project, while NEW-ARGENT considered the assimilation of GNSS along slant paths.
The approach used in both projects is the VSF (Very Short-term Forecast) in which a 6h data assimilation phase is followed by a 6h forecast. In addition, both projects used the WRF model and the 3DVar data assimilation system of CNR-ISAC (Federico, 2013; Torcasio et al., 2024).
The ICREN project focuses over northern Italy, where intense convective events occur since late spring to early fall. More than 100 case studies were considered and GNSS-ZTD was assimilated with and without lightning data. Different strategy of simulations were considered and results show the important role of the VSF forecast and data assimilation in predicting convective rainfall. Specifically, the assimilation of lightning was very useful for the first hours of forecast improving substantially the prediction of intense precipitation (higher than 30 mm/3h). In any case, assimilating lightning was useful also at lower precipitation thresholds. The GNSS-ZTD data assimilation had a lower impact on the precipitation forecast, nevertheless it improved the forecast for all precipitation thresholds. However, the combination of both data had the largest impact on the precipitation forecast, especially for the forecast period from 1h to 4h after the ending of the assimilation phase. Finally, the ICREN project showed a significant impact of the GNSS-ZTD and lightning data assimilation up to 6h forecast.
The NEW-ARGENT project considered four months (May, June and October 2023, and September 2022) and focused on the assimilation of GNSS along slant paths for three regions: Lazio, Lombardy and Sicily. This problem was firstly solved assimilating GNSS gradient that partially recover the anisotropy of GNSS observations. Specifically, we compared the precipitation forecast at the short-range in four different experiments set-up: CTRL (control), without GNSS data assimilation, GNSS-ZTD, with the assimilation of GNSS zenith delay, GNSS-GRA, in which the gradients are assimilated, and GNSS-ZTD-GRA, in which both the gradients and the zenith total delay are assimilated.Results show that the assimilation of the gradients, both alone and with the GNSS-ZTD, is beneficial for the improvement of precipitation forecast of convective events over Italy.
References
Federico, S.: doi:10.5194/amt-6-3563-2013, 2013.
Torcasio, R.C.; et al.: https://doi.org/10.3390/rs16101769, 2023.
Acknowledgments
This work has been realized in the projects PRIN-PNRR NEW-ARGENT (MUR contract- P20228LMA2) and ICREN-PRIN project (MUR- CUP: D53D23004770006).
How to cite: Federico, S., Realini, E., Torcasio, R. C., Transerici, C., Venuti, G., Song, X., and Crespi, M.: Assimilation of GNSS data over Italy: the results of ICREN and NEW-ARGENT projects, EMS Annual Meeting 2025, Ljubljana, Slovenia, 7–12 Sep 2025, EMS2025-520, https://doi.org/10.5194/ems2025-520, 2025.
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