Downscaling ERA5 reanalysis for coastal climate applications in the Mediterranean area: preliminary results

The management of coastal zones requires accurate data concerning past wind/wave regimes and future climate trends. Previous studies are mostly intended to establish the intersection of the expected mean sea level with the current shore profile. Nevertheless, it is important to consider that any morphodynamic equilibrium response of the coasts has time scales shorter than those of climate change. Many studies have been based on low resolution reanalyses that cannot allow a detailed description of the variability induced by local conditions. We present a feasibility study where a simple dynamical downscaling of ERA5 reanalysis data is applied through a cascade of regional atmospheric/wave models. The final goal of this study is to identify the long-term trends in the last 30-35 years in order to better understand the past impacts of climate change along the coast. The methodology applied is based on: a high resolution atmospheric model (WRF-ARW), run at a horizontal resolution of about 3 km and a finite element wave model (WW3), able to compute high-resolution waves along the coast, at a resolution up to 500 meters. The target area is the North-Western Mediterranean. We present the preliminary results regarding the characteristics of such high-resolution wind/wave data and a comparison with local observed data and global reanalyses. This work is part of the activities foreseen in the framework of the MAREGOT Project (www.lamma.rete.toscana.it/en/maregot), funded by the EU (Italian-France Cross-border program), to which the LaMMA Consortium is involved as a partner