DATE2022-05-26 23:24:34
TITLENext-generation atmospheric-ocean climate modelling for extreme sea level hazard projections in the Adriatic Sea
AUTHORSCléa Denamiel (1) ,Ivica Vilibić (1)
  1. 1) Ruđer Bošković Institute, Zagreb (Croatia)
ABSTRACTToday, about 10% of the world population lives not more than 10 km from the coastline, being extremely vulnerable to coastal floods and extreme sea-levels. Aside from mean sea level rise, extreme sea levels are strongly influenced by local processes driven by coastal topographies and geomorphologies. For example, in the Adriatic Sea, sirocco-driven storm surges may vary substantially within the lagoons (e.g., Venice Lagoon) or meteorologically-driven tsunami waves may change for several times over a few kilometres, like in Vela Luka Bay. Adriatic storm surge models are nowadays capable to provide coastal flood forecasts (with some reliability) at (sub-)kilometre-scale resolution in operational mode. However, till recently, climate projections of extreme sea levels at kilometre-scale (or higher) resolutions, were relying on atmospheric forcing coming from regional climate models available at about 10 km resolution and thus strongly underestimating local processes, such as the bora wind, in the Adriatic Sea. Consequently, we developed the AdriSC (Adriatic Sea and Coast) coupled atmosphere-ocean kilometre-scale climate model to better assess extreme sea level hazards along the Adriatic coast. The AdriSC climate modelling suite is composed of two modules, which can be used independently or together to quantify a variety of climate-related processes. The general circulation module – coupling online an atmospheric model (Weather Research and Forecasting, WRF) at up to 3 km resolution and an ocean model (Regional Ocean Modelling System, ROMS) at up to 1 km resolution – has been run for 31-year long periods at an extreme computational cost (i.e., each simulation took 18 months using 260 CPUs on the European Centre for Middle-range Weather Forecast (ECMWF) supercomputing facility). Further, the extreme event module – coupling offline the WRF model downscaled to 1.5 km resolution and the unstructured ADCIRC-SWAN storm surge model at up to 10 m resolution – has been used for the most extreme sea level events previously extracted from the long-term simulations following classical hazard assessment techniques (i.e. about 80 short-term simulations). In this talk, we will present (1) the evaluation of the extreme sea-levels provided by the AdriSC model, (2) the changes in kilometer-scale extreme sea-levels under extreme climate warming over the whole Adriatic, inside some vulnerable sub-basins, and along the coastline, (3) the present and projected kilometer-scale extreme sea level hazard assessments and finally, (4) the resulting sub-kilometer scale distributions of wind speed, wind direction, sea level, significant wave height, peak wave period, etc. With this study we will also demonstrate the importance to use higher-resolution climate model to help local decision makers better mitigate the impact of extreme sea-level under climate warming.