Multi-Physics Ensemble approach to investigate two summer 2021extreme Heat Waves over central Mediterranean basin
Authors: Ricchi Antonio , Sangelantoni Lorenzo , Redaelli Gianluca , Ferretti Rossella 
Published: June 2022

&lt;p&gt;&lt;span&gt;H&lt;/span&gt;&lt;span&gt;eatwaves (HWs) is&amp;#160;&lt;/span&gt;&lt;span&gt;high-impact phenomena that may have devastating impacts on &lt;/span&gt;&lt;span&gt;societies and ecosystems&lt;/span&gt;&lt;span&gt;.&lt;/span&gt; &lt;span&gt;In the context of &lt;/span&gt;&lt;span&gt;numerical &lt;/span&gt;&lt;span&gt;modeling&lt;/span&gt;&lt;span&gt;, despite&lt;/span&gt;&lt;span&gt;&amp;#160;&lt;/span&gt;&lt;span&gt;driving &lt;/span&gt;&lt;span&gt;synoptic scale &lt;/span&gt;&lt;span&gt;dynamics &lt;/span&gt;&lt;span&gt;are generally well caught&lt;/span&gt;&lt;span&gt;,&lt;/span&gt; &lt;span&gt;local&lt;/span&gt;&lt;span&gt;-&lt;/span&gt;&lt;span&gt;scale&lt;/span&gt; &lt;span&gt;forcing&amp;#160;&lt;/span&gt;&lt;span&gt;representation &lt;/span&gt;&lt;span&gt;is &lt;/span&gt;&lt;span&gt;still &lt;/span&gt;&lt;span&gt;challenging, embodying a source of uncertainty and errors&lt;/span&gt;&lt;span&gt;. &lt;/span&gt;&lt;span&gt;In this work we &lt;/span&gt;&lt;span&gt;study&lt;/span&gt;&lt;span&gt; two&lt;/span&gt; &lt;span&gt;HW&lt;/span&gt;&lt;span&gt;s&lt;/span&gt; &lt;span&gt;occurring &lt;/span&gt;&lt;span&gt;in&lt;/span&gt;&lt;span&gt; 2021 summer season &lt;/span&gt;&lt;span&gt;(02-05 Aug and 11-14 Aug), on the Italian territory. &lt;/span&gt;&lt;span&gt;The first&lt;/span&gt;&lt;span&gt; event&lt;/span&gt;&lt;span&gt;, &lt;/span&gt;&lt;span&gt;is &lt;/span&gt;&lt;span&gt;characterized by &lt;/span&gt;&lt;span&gt;strong &lt;/span&gt;&lt;span&gt;South-West&lt;/span&gt;&lt;span&gt;erly winds&lt;/span&gt; &lt;span&gt;and&lt;/span&gt; &lt;span&gt;albeit with&lt;/span&gt;&lt;span&gt;out&lt;/span&gt;&lt;span&gt;&amp;#160;high &lt;/span&gt;&lt;span&gt;geopotential&lt;/span&gt;&lt;span&gt; and 850 &lt;/span&gt;&lt;span&gt;h&lt;/span&gt;&lt;span&gt;P&lt;/span&gt;&lt;span&gt;a &lt;/span&gt;&lt;span&gt;temperature &lt;/span&gt;&lt;span&gt;caused&lt;/span&gt; &lt;span&gt;2 m &lt;/span&gt;&lt;span&gt;temperatures &lt;/span&gt;&lt;span&gt;above&lt;/span&gt;&lt;span&gt; 40 &amp;#176;C &lt;/span&gt;&lt;span&gt;in the central Italy east cost &lt;/span&gt;&lt;span&gt;(&lt;/span&gt;&lt;span&gt;e.g., &lt;/span&gt;&lt;span&gt;in the urban area of &lt;/span&gt;&lt;span&gt;Pescara&lt;/span&gt;&lt;span&gt;), mainly &lt;/span&gt;&lt;span&gt;driven&lt;/span&gt; &lt;span&gt;by &lt;/span&gt;&lt;span&gt;katabatic&lt;/span&gt; &lt;span&gt;winds&lt;/span&gt; &lt;span&gt;(&lt;/span&gt;&lt;span&gt;i.e., &lt;/span&gt;&lt;span&gt;Fhoen&lt;/span&gt;&lt;span&gt; dynamics). The second &lt;/span&gt;&lt;span&gt;HW&lt;/span&gt;&lt;span&gt;, &lt;/span&gt;&lt;span&gt;has been triggered by a strong advection &lt;/span&gt;&lt;span&gt;of hot air from the North African territory and &lt;/span&gt;&lt;span&gt;with &lt;/span&gt;&lt;span&gt;a major impact on the western coasts of the Italian territory.&lt;/span&gt;&amp;#160;&lt;span&gt;Here, &lt;/span&gt;&lt;span&gt;we &lt;/span&gt;&lt;span&gt;leverage a &lt;/span&gt;&lt;span&gt;WRF (Weather Research and Forecasting system) &lt;/span&gt;&lt;span&gt;numerical model &lt;/span&gt;&lt;span&gt;at &lt;/span&gt;&lt;span&gt;1 km resolution &lt;/span&gt;&lt;span&gt;over&lt;/span&gt;&lt;span&gt; central Italy&lt;/span&gt;&lt;span&gt; multi-physics ensemble&lt;/span&gt;&lt;span&gt;, &lt;/span&gt;&lt;span&gt;including &lt;/span&gt;&lt;span&gt;various&lt;/span&gt; &lt;span&gt;Planetary Boundary Layer (&lt;/span&gt;&lt;span&gt;PBL&lt;/span&gt;&lt;span&gt;)&lt;/span&gt;&lt;span&gt;, &lt;/span&gt;&lt;span&gt;land-surface-model&lt;/span&gt;&lt;span&gt; (LSM)&lt;/span&gt;&lt;span&gt;, radiative and surface &lt;/span&gt;&lt;span&gt;numerical scheme&lt;/span&gt;&lt;span&gt;s&lt;/span&gt;&lt;span&gt;. The simulations &lt;/span&gt;&lt;span&gt;are&lt;/span&gt; &lt;span&gt;performed using an approach that takes into account the evolution of sea &lt;/span&gt;&lt;span&gt;surface &lt;/span&gt;&lt;span&gt;temperature &lt;/span&gt;&lt;span&gt;and &lt;/span&gt;&lt;span&gt;Marine Mixed&lt;/span&gt;&lt;span&gt; Layer Depth &lt;/span&gt;&lt;span&gt;(&lt;/span&gt;&lt;span&gt;at &lt;/span&gt;&lt;span&gt;high resolution, 4.5 km), according to the OML numerical scheme,&amp;#160;&lt;/span&gt;&lt;span&gt;in order to represent the air-sea interactions&lt;/span&gt;&lt;span&gt; more realistically&lt;/span&gt;&lt;span&gt;. The preliminary results show a &lt;/span&gt;&lt;span&gt;relevant&lt;/span&gt; &lt;span&gt;impact &lt;/span&gt;&lt;span&gt;exerted &lt;/span&gt;&lt;span&gt;by&lt;/span&gt;&lt;span&gt; numerical parameterizations, in the prediction of the maximum temperature and humidity, especially in the urban area&lt;/span&gt;&lt;span&gt;s&lt;/span&gt;&lt;span&gt;. A notable impact is also observed &lt;/span&gt;&lt;span&gt;for&lt;/span&gt; &lt;span&gt;the simulation of the minimum temperature values. The greatest &lt;/span&gt;&lt;span&gt;modulation&lt;/span&gt; &lt;span&gt;of HWs reproduction &lt;/span&gt;&lt;span&gt;results from the choice of LSM&lt;/span&gt;&lt;span&gt;and PBL &lt;/span&gt;&lt;span&gt;schemes&lt;/span&gt;&lt;span&gt;,&lt;/span&gt;&lt;span&gt; and their combinations. These results highlight that&lt;/span&gt;&amp;#160;&lt;span&gt;the multi-physics approach is &lt;/span&gt;&lt;span&gt;also &lt;/span&gt;&lt;span&gt;useful to highlight most relevant processes driving local-scale modulation and &lt;/span&gt;&lt;span&gt;related&lt;/span&gt;&lt;span&gt; uncertainty representing &lt;/span&gt;&lt;span&gt;a valuable tool to foster local-scale HWs-related risk mitigation.&lt;/span&gt;&lt;/p&gt;