Federico et al. (2025) Forecasting convective precipitation over northern Italy: A comparison of lightning and GNSS-ZTD data assimilation

Identification

• Journal: Atmospheric Research
• Year: 2025
• Date: 2025-12-09
• Authors: Stefano Federico, Rosa Claudia Torcasio, Claudio Transerici, Eugenio Realini, Xiangyang Song, G. Venuti
• DOI: 10.1016/j.atmosres.2025.108687

Research Groups

• National Research Council of Italy, Institute of Atmospheric Sciences and Climate (CNR-ISAC), Rome, Italy
• Department of Civil and Environmental Engineering, Politecnico di Milano, Italy
• Geomatics Research & Development srl (GReD), Lomazzo, Italy

Short Summary

This study evaluates the impact of assimilating lightning and Global Navigation Satellite System – Zenith Total Delay (GNSS-ZTD) data on short-range (up to 6 hours) forecasts of intense convective precipitation over Northern Italy, demonstrating that both data sources, particularly when combined, significantly enhance forecast accuracy.

Objective

• To assess the impact of lightning and GNSS-ZTD data assimilation, individually and combined, on short-range (up to 6 hours) forecasts of intense convective precipitation events over Northern Italy.

Study Configuration

• Spatial Scale: Northern Italy, with radar observations focused on the Lombardy Region.
• Temporal Scale: 116 convective precipitation cases from April to September 2019, with forecasts extending up to 6 hours.

Methodology and Data

• Models used: Weather and Research Forecast (WRF) model. Data assimilation techniques included nudging for lightning data and 3DVar for GNSS-ZTD data.
• Data sources: Lightning data, Global Navigation Satellite System – Zenith Total Delay (GNSS-ZTD) data for assimilation. Radar observations over the Lombardy Region were used for verification.

Main Results

• Both lightning data assimilation and GNSS-ZTD data assimilation individually improved short-range convective precipitation forecasts.
• A statistical test confirmed that the forecast improvement was significant across several precipitation thresholds and time ranges.
• Assimilating both lightning and GNSS-ZTD data concurrently yielded a greater positive impact on forecasts compared to assimilating either data source alone.
• Forecast performance exhibited a slight decrease with increasing forecast time, while the positive impact of data assimilation decreased more rapidly.
• A sensitivity test aimed at reducing false alarms produced contradictory results.

Contributions

• Provides a comprehensive comparison of the individual and combined impacts of lightning and GNSS-ZTD data assimilation on short-range convective precipitation forecasts over Northern Italy.
• Demonstrates the synergistic benefits of assimilating both lightning and GNSS-ZTD data for enhanced forecast accuracy of intense rain events.
• Quantifies the statistical significance of forecast improvements across various precipitation thresholds and forecast lead times.

Funding

• Not explicitly mentioned in the provided text.

Citation

@article{Federico2025Forecasting,
  author = {Federico, Stefano and Torcasio, Rosa Claudia and Transerici, Claudio and Realini, Eugenio and Song, Xiangyang and Venuti, G.},
  title = {Forecasting convective precipitation over northern Italy: A comparison of lightning and GNSS-ZTD data assimilation},
  journal = {Atmospheric Research},
  year = {2025},
  doi = {10.1016/j.atmosres.2025.108687},
  url = {https://doi.org/10.1016/j.atmosres.2025.108687}
}