Seminar: High-resolution regional reanalyses over Italy: motivation, validation, applications and perspectives

Part of the Cycle of seminars: Understanding and managing climate risk

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High-resolution regional reanalyses over Italy: motivation, validation, applications and perspectives

Atmospheric reanalyses provide an optimal reconstruction of past atmospheric states by combining Numerical Weather Prediction (NWP) simulations with observational data of the global observing system through data assimilation. This combination overcomes the inherent limitations of the singular components and exploits the benefits of both, delivering temporal consistent, physically coherent and homogeneous datasets over multiple decades. While global reanalyses have become a key tool for the study of climate and weather, regional reanalyses over limited-area domains are increasingly recognized as essential for representing atmospheric processes at high spatial and temporal resolution. In particular, such datasets enable a realistic representation of local-scale processes, including convection and land-atmosphere interactions over complex topography.

Over Italy, several convection-permitting regional reanalyses have been developed in recent years through the dynamical downscaling of the global ERA5 reanalysis using different numerical models (COSMO, WRF, MOLOCH). Further developments are foreseen, including the production of ITINERE, a new high-resolution reanalysis planned by the ItaliaMeteo Agency, based on the ICON model framework and a state-of-the-art data assimilation technique.

This seminar will provide a comprehensive overview of these high-resolution regional reanalyses. The motivations behind the developments of these convection-permitting retrospective datasets will be presented, with a particular focus towards the multi-year validation results for both daily and hourly temperature and precipitation fields, highlighting the systematic improvements achieved with respect to the global reanalysis ERA5, currently considered the state of the art. The seminar will also illustrate a range of applications, demonstrating the added value of the convection-permitting datasets for a variety of processes.

Finally, future perspectives will be discussed, including the role of multi-decadal high-resolution atmospheric reanalyses in supporting the development of next-generation data-driven models based on machine-learning techniques. Indeed, this approach is already reshaping the world of weather prediction, as shown by the emergence of the first artificial intelligence forecasting systems trained on reanalysis datasets, such as AIFS or AICON, which complement traditional physics-based modelling frameworks.

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Contact: Marco Gaetani — marco.gaetani@iusspavia.it