Atmospheric rivers — long corridors with high concentrations of water vapour that move from tropical regions towards higher latitudes — play a significant role in rainfall across the Iberian Peninsula, accounting for up to around 30 percent of annual precipitation in northern regions. This is one of the main conclusions of a study developed in collaboration with researchers from the University of Aveiro (UA).
The study provides a detailed analysis of the influence of these atmospheric systems on regional precipitation patterns and was carried out by Diogo Luís, a PhD student at CESAM/DAO, Carla Gama, a researcher at CESAM/DAO, Cátia Gonçalves, and José M. Castanheira, a CESAM researcher and professor at the Department of Physics of the University of Aveiro. The work also involved researchers from the Karlsruhe Institute of Technology, in Germany, and the Swiss Federal Institute of Technology Zurich, in Switzerland. It was led by Irina Gorodetskaya, who initiated this line of research on atmospheric rivers at UA and is currently a researcher at the Interdisciplinary Centre of Marine and Environmental Research (CIIMAR) of the University of Porto.
To better understand the impact of these meteorological systems, the team analysed 42 years of climate data, from 1979 to 2020, using high-resolution ERA5 reanalysis data from the European Centre for Medium-Range Weather Forecasts (ECMWF), E-OBS data — a dataset produced by the European Climate Assessment & Dataset (ECA&D) project — and meteorological station records. In total, 580 persistent atmospheric rivers were identified, defined as events lasting at least 18 hours, corresponding to an annual average of 13.8 episodes affecting the Iberian Peninsula.
The results show that the northwestern coastal areas of the Iberian Peninsula are frequently affected by these moisture corridors. Among the years analysed, 2013 stood out as the most active, with the highest number of persistent episodes recorded.
The study also examined the relationship between these moisture corridors and associated meteorological systems, concluding that atmospheric rivers occur more frequently in connection with cold fronts than with warm fronts of extratropical cyclones. The highest precipitation values associated with this phenomenon were also more frequently observed near cold fronts. To further investigate this dynamic, the researchers analysed three significant episodes in detail: a storm that occurred in October 1979, Storm Gong, and Storm Ana.
By combining observational data with high-resolution reanalysis datasets, the study reinforces the importance of atmospheric rivers in shaping regional rainfall patterns. In addition, their association with extratropical systems highlights the need for more fundamental studies on the thermohydrodynamics of the atmosphere, in order to better understand the genesis of these events, extend the forecasting window for extreme precipitation, and support the earlier issuing of warnings.
Original news: UA Notícias, 25 May 2026.