Hazardous Mediterranean cyclones in the current and future climate

Mediterranean cyclones are far less understood than cyclones over major ocean basins yet can lead to devastating socio-economic impacts. The processes often associated with their cyclogenesis (southwards intrusions of cold stratospheric air extending over several 1000 km from the midlatitudes) necessitate large model domains but processes associated with their intensification (such as air-sea interactions and deep convection) typically require "convection-permitting" resolutions with grid boxes < around 6 km to be adequately simulated.

In addition, coupling of an atmospheric model to other model components such as those representing ocean, waves or dust may also be important for skilful forecasting. The range of atmospheric processes involved and their interaction with the underlying sea surface makes simulating Mediterranean cyclones challenging, limiting our current forecast skill and projections of how these cyclones may change in the future.

The overarching aim is to quantify and characterize the importance of air-sea interactions and deep convection in driving the development of hazardous Mediterranean cyclones in both the current and future climate.

1. How do processes generating heat (ocean surface fluxes, convective clouds, atmospheric radiation) modify Mediterranean cyclones and their associated hazards (winds and rain)?

2. How sensitive are Mediterranean cyclones to typical uncertainties in sea surface temperatures and the locations of mid-latitude features such as streamers or cut-off lows that are critical for their cyclogenesis? 3. How important are interactions between the atmosphere and oceans, waves and dust to obtaining skilful forecasts?

4. How do the answers to the above questions change in a future warmer climate?

The Met Office operationally performs convection-permitting forecasting over the UK, and in selected other locations, e.g., Southeast Asia, but does not have an operational configuration over the Mediterranean basin. This region is challenging due to the complex orography, strong surface fluxes from the sea, and intruding mid-latitude weather features.

The student will begin with an (atmosphere-only) convection-permitting configuration of the Met Office's weather forecast model (the MetUM), developed and successfully used by the Met Office co-supervisor, Sánchez, to simulate Mediterranean "hurricane" Ianos. They will further develop this configuration, including evaluating the importance of resolution and the representation of the ocean surface, and understand its capabilities and limitations.

The applicability of the Met Office's "new unified physics approach" (rather than separate tropical and mid-latitude regional configurations) will be explored in this region which has mixed tropical and mid-latitude characteristics. The effects of new Met Office deep convection and microphysics schemes will also be explored. We will exploit new community large-ensemble climate change simulations (performed by the NERC-funded CANARI project) to quantify the changing diabatic influence. Convection-permitting future climate cases will be simulated by downscaling these simulations.