A Framework for Convection-Permitting Climate Downscaling over Southern Italy

Projecting climate change impact in southern Italy is particularly challenging because this region is located in the center of the Mediterranean basin, which is a recognized climate change hotspot, and is characterized by steep and complex orography requiring analysis at high spatial resolution. Therefore, climate models at the convection-permitting scale considerably improve the ability to simulate water cycle trends in that region, especially severe events.

This note introduces the modeling framework on which climate simulations are being carried out for southern Italy using CMIP6 projections and presents the first results related to the comparison of the historical simulation with observational datasets. A preliminary analysis revealed that the best CMIP6 global climate model (GCM) for reproducing the interannual cycle of precipitation and temperature over the study area is the High-Resolution MPI-ESM-1-2 model (1°x1° as horizontal resolution). Such a GCM was chosen to provide 6-hour boundary conditions for dynamic downscaling with the WRF (Weather Research and Forecasting) limited-area model with two domains one-way nested: the external one D01, with a horizontal resolution of about 20km, covering the entire Mediterranean area (209x214 grid points), and the internal one D02, with a horizontal resolution of about 4km, centered on southern Italy (285x265 grid points). The historical simulation extends from 1995 to 2014. The future simulations cover the period 2025 to 2045. The first future simulation employs the SSP 5-8.5 scenario.

Total precipitation and near-surface air temperature resulting from the historical simulation are compared with both observational datasets (namely, the spatially distributed products BigBang, SCIA, E-OBS, and validated weather station time series) and reliable downscaled reanalyses (e.g., ERA5-Land, MERIDA, MERIDA HRES, SPHERA, CERRA, VHREA_IT), which are increasingly available for the Italian peninsula. The results highlight that the evaluation of the performance of the historical simulation is partially affected by the selection of the reference dataset.

 

 

Acknowledgments: This study was funded by the Next Generation EU - Italian NRRP, Mission 4, Component 2, Investment 1.3, project WaterWISE - Water Management Strategies and Climate Change Adaptation in Southern Italy, n. PE00000005, CUP D43C22003030002; and by the Next Generation EU - Italian NRRP, Mission 4 ‘Education and Research’ - Component C2, Investment 1.1, Research Project of National Interest (PRIN 2022 PNRR) ­- An integrated modeling approach for mitigating climate CHANge effects through enhanCEd weathering in Southern Italy (CHANCES, CUP H53D23011260001), Italian Ministry of University and Research.