Mediterranean hurricanes (Medicanes) are intense cyclones that acquire tropical characteristics, associated with extreme winds and rainfall, thus posing a serious natural hazard to populated areas along Mediterranean coasts. Understanding how Medicanes will change with global warming remains, however, a challenge, because coarse resolution and/or the lack of atmosphere‐ocean coupling limit the reliability of numerical simulations. Here we investigate the Medicanes' response to global warming using a recently developed 25‐km global coupled climate model, which features a realistic representation of Medicanes in present climate conditions. It is found that despite a decrease in frequency, Medicanes potentially become more hazardous in the late century, lasting longer and producing stronger winds and rainfall. These changes are associated with a more robust hurricane‐like structure and are mainly confined to autumn. Thus, continued anthropogenic warming will increase the risks associated with Medicanes even in an intermediate scenario (Representative Concentration Pathway, RCP4.5), with potential natural and socioeconomic consequences.
Medicanes are tropical-like cyclones that develop in the Mediterranean Sea. Due to their harmful potential, the study of medicanes has captured great attention from the scientific community. In the context of a changing climate, their future climatological characterization can only be achieved using climate model output. A frequently used method to characterize the thermal structure of medicanes is the cyclone phase space (CPS) described by Hart (2003). This requires geopotential data from 300 to 900 hPa every 50 hPa. However, in long, high-resolution climate simulations, model output requires very high storage space and only data from a few geopotential levels are saved. To overcome the lack of geopotential data at some levels, available data are vertically interpolated to obtain data for the 13 levels required. In this work, we use high horizontal resolution data from the ERA-5 reanalysis (1979-2018) to analyse the climatology of medicanes simulated using the 13 vertical levels required according to Hart (2003), as well as different combinations of geopotential data from a few selected levels. Our results allow us to propose, for the first time, a limited set of recommended geopotential levels required for an adequate climatological characterization of medicanes in the perspective of long climate change simulations, taking into account the associated limitations of output data storage.
Cyclones with tropical characteristics called medicanes (“Mediterranean Hurricanes”) eventually develop in the Mediterranean Sea. They have large harmful potential and a correct simulation of their evolution in climate projections is important for an adequate adaptation to climate change. Different studies suggest that ocean–atmosphere coupled models provide a better representation of medicanes, especially in terms of intensity and frequency. In this work, we use the regionally‐coupled model ROM to study how air‐sea interactions affect the evolution of medicanes in future climate projections. We find that under the RCP8.5 scenario our climate simulations show an overall frequency decrease which is more pronounced in the coupled than in the uncoupled configuration, whereas the intensity displays a different behaviour depending on the coupling. In the coupled run, the relative frequency of higher‐intensity medicanes increases, but this is not found in the uncoupled simulation. Also, this study indicates that the coupled model simulates better the summer minimum in the occurrence of medicanes, avoiding the reproduction of unrealistically intense events that can be found in summer in the uncoupled model.
<p>Several Medicanes, which have been previously analyzed in the literature, have been studied using ERA-5 reanalyses to identify the environment in which they develop and possibly distinguish tropical-like cyclones from warm seclusions. Initially, the cyclone phase space was analyzed to identify changes in the environmental characteristics. Subsequently, the temporal evolution of several parameters was considered, including sea surface fluxes, CAPE, coupling index, potential intensity, baroclinicity.</p> <p>Although the results are not consistent for all cyclones, some general characteristics can be identified: cyclones develop in areas of moderate-to-high baroclinicity associated with intense jet streams, while in the mature stage the environment becomes less baroclinic. A general reduction in the horizontal extent of the cyclone can be observed as the cyclones begin to show a shallow warm core. In this phase a progressive reduction of the CAPE can be observed in proximity of the cyclone center. Finally, the wind speed appears strongly underestimated compared to the observations, raising some concerns about the applicability of ERA-5 for the detection of wind features.</p>
<p><span><span>Medicanes are tropical-like cyclones that </span></span><span><span>form</span></span><span><span> in the Mediterranean Sea. Due to their harmful potential, the </span></span><span><span>characterization</span></span><span><span> of medicanes has </span></span><span><span>become an increasingly-studied topic within the</span></span><span><span> scientific community. In the </span></span><span><span>current</span></span><span><span> context of </span></span><span><span>climate change</span></span><span><span>, their future characterization </span></span><span><span>from a climatological perspective</span></span><span><span> can only be </span></span><span><span>attained</span></span><span><span> using </span></span><span><span>high resolution </span></span><span><span>climate model output. </span></span><span><span>T</span></span><span><span>he thermal structure of medicanes is </span></span><span><span>generally examined with</span></span><span><span> the Cyclone Phase Space (CPS) described </span></span><span><span>in</span></span><span> </span><span><span>Hart (2003)</span></span><span><span>. This </span></span><span><span>necessitates</span></span><span><span> geopotential data from 300 hPa to </span></span><span><span>9</span></span><span><span>00 hPa every 50 hPa. </span></span><span><span>Notwiths</span></span><span><span>t</span></span><span><span>anding</span></span><span><span>, in long, high-resolution climate simulations, model output requires very high storage space and only data from a few geopotential levels are </span></span><span><span>typically</span></span><span><span> saved. To overcome the lack of geopotential data at some levels, available </span></span><span><span>model</span></span><span><span> data are vertically interpolated </span></span><span><span>in order </span></span><span><span>to obtain data for the 13 levels required. In this work, we use high</span></span><span><span> horizontal </span></span><span><span>resolution data from the ERA-5 reanalysis (1979 - 2018) to analyze the climatology of medicanes simulated using the 13 vertical levels required </span></span><span><span>based on</span></span><span> </span><span><span>Hart (2003)</span></span><span><span>, as well as different combinations of geopotential data from a few selected levels. Our results allow us to propose, for the first time, a limited se</span></span><span><span>t</span></span><span><span> of recommended geopotential levels </span></span><span><span>needed</span></span><span> </span><span><span>to adequately </span></span><span><span>detect</span></span><span><span> medicanes in long, </span></span><span><span>high resolution</span></span><span><span> climate change simulations, taking into account the associated limitations of output data sto</span></span><span><span>rage</span></span><span><span>.</span></span></p>
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