Mediterranean cyclones can lead to devastating socio-economic impacts but are far less studied and understood than cyclones tracking over the open ocean basins. One reason for these differences is the modelling challenge of including a good representation of diabatic processes, such as convection and heat/moisture fluxes from the ocean, in domains large enough to capture important synoptic-scale dynamics such as potential vorticity streamers as well as interactions with the surrounding complex orography. Diabatic process representation is likely to be particularly important for the medicane (“Mediterranean hurricane”) subset of Mediterranean cyclones; medicanes are intense cyclones that share characteristics with tropical cyclones such as a cloudless eye in satellite imagery. While previous research has assessed the role of diabatic processes in individual case studies and/or using resolutions that require parametrization of convection, it remains unclear whether the sensitivity of modelled Mediterranean cyclones to explicit representation of convection is robust across cyclone types.

Here I present our recent work from two studies on Mediterranean cyclones. The first study addresses forecast dependence to model resolution and physics across seven cyclones with a range of characteristics; convection-permitting km-scale resolution simulations are compared to simulations using resolutions typical of operational global forecast models which require a convection parametrization scheme. The second study considers two contrasting cyclones and addresses the range of cyclone intensities possible for plausible changes in sea surface temperatures. We demonstrate that (1) the forecast skill of hazardous Mediterranean cyclones depends critically on the interaction between model resolution and physical parameterisations, implying that improvements in kilometre-scale forecasting require advances in model physics as well as increased resolution, and (2) plausible sea surface temperature changes can have a significant impact on medicanes but that other cyclone types are much less impacted, implying that the impact of future changes in sea surface temperatures will be dependent on cyclone type.

Suzanne Gray (Professor at Univ. Reading, meteorology department).

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