Multi-Physics Ensemble approach to investigate two summer 2021extreme Heat Waves over central Mediterranean basin

Heatwaves (HWs) is high-impact phenomena that may have devastating impacts on societies and ecosystems. In the context of numerical modeling, despite driving synoptic scale dynamics are generally well caught, local-scale forcing representation is still challenging, embodying a source of uncertainty and errors. In this work we study two HWs occurring in 2021 summer season (02-05 Aug and 11-14 Aug), on the Italian territory. The first event, is characterized by strong South-Westerly winds and albeit without high geopotential and 850 hPa temperature caused 2 m temperatures above 40 °C in the central Italy east cost (e.g., in the urban area of Pescara), mainly driven by katabatic winds (i.e., Fhoen dynamics). The second HW, has been triggered by a strong advection of hot air from the North African territory and with a major impact on the western coasts of the Italian territory. Here, we leverage a WRF (Weather Research and Forecasting system) numerical model at 1 km resolution over central Italy multi-physics ensemble, including various Planetary Boundary Layer (PBL), land-surface-model (LSM), radiative and surface numerical schemes. The simulations are performed using an approach that takes into account the evolution of sea surface temperature and Marine Mixed Layer Depth (at high resolution, 4.5 km), according to the OML numerical scheme, in order to represent the air-sea interactions more realistically. The preliminary results show a relevant impact exerted by numerical parameterizations, in the prediction of the maximum temperature and humidity, especially in the urban areas. A notable impact is also observed for the simulation of the minimum temperature values. The greatest modulation of HWs reproduction results from the choice of LSMand PBL schemes, and their combinations. These results highlight that the multi-physics approach is also useful to highlight most relevant processes driving local-scale modulation and related uncertainty representing a valuable tool to foster local-scale HWs-related risk mitigation.