Diabatic influences on current and future hazardous Mediterranean cyclones
Lead Research Organisation:
University of Reading
Department Name: Meteorology
Abstract
The Mediterranean basin is home to diverse storms from weak systems generated by air interacting with mountains to intense cyclones (also termed "depressions"). A subset of cyclones, medicanes (Mediterranean hurricanes), resemble hurricanes and can be particularly devastating; e.g., the winds of medicane Ianos were equivalent to a category two hurricane on its landfall in Greece in 2020 causing infrastructure damage and fatalities. Mediterranean cyclones have been far less studied than their relatives crossing the North Atlantic, despite being responsible for up to 80% of the local winter-time extreme precipitation. They are more challenging to forecast due to their typically smaller scale and shorter lifetime; the effects of the nearby mountains and warm, semi-enclosed Mediterranean Sea on their development and impacts; and the influence of both the subtropical and extratropical climatic zones. These cyclones are driven by interactions between processes occurring at different spatial scales: fluxes of heat and moisture from the ocean surface together with latent heat fluxes from deep convective clouds (so-called diabatic processes), and planetary-scale deviations of the polar jet at about 10km altitude that cause the intruding air streamers that commonly precede their genesis. Studies indicate that the Mediterranean region is particularly vulnerable to climate change and as the climate warms there will likely be fewer, but more hazardous, medicanes. We propose to generate new knowledge of the role of diabatic processes in driving the development of hazardous Mediterranean cyclones in both the current and future climate.
The aims are to
* Quantify the influence of diabatic processes on intense Mediterranean cyclones and determine how they modify the track and intensity of cyclones and their hazardous winds and rainfall;
* Simulate and analyse changes in plausible worst case Mediterranean cyclones with climate change and quantify the changing importance of diabatic influences; and
* Synthesize the knowledge gained considering implications for forecasting and climate change mitigation and applicability to related weather systems beyond the Mediterranean, particularly subtropical cyclones.
Importantly, the atmospheric numerical model we use will have a model grid with points separated by just a few km, fine enough to be able to directly represent deep convection without the approximations that are known to misrepresent interactions between convection and larger scales. We will combine this atmospheric model with an ocean model, so-called coupling, to assess the importance of changes in the sea surface temperatures through ocean mixing. Such km-scale coupled modelling is state-of-the-art and is only now possible through advances in environmental prediction modelling. We will interrogate our model output using advanced diagnostic tools to trace the diabatic processes from their generation to weather impacts. For our climate change work we will leverage new community large-ensemble climate change simulations to drive our km-scale cyclone forecasts.
The benefits will be (1) new process-level knowledge of the importance of diabatic processes across spatial scales, (2) insight into plausible worst-case future cyclones, (3) cost-benefit analysis of km-scale coupled models for cyclone representation, (4) a synthesis that includes the implications of the findings for related weather systems across the globe, and (5) a new UK research capability for km-scale coupled modelling over the Mediterranean basin. These benefits will translate into impacts through our close collaboration with our project partners (including the Met Office) and engagement in active Mediterranean cyclones interdisciplinary research networks funded by EU COST Actions.
The aims are to
* Quantify the influence of diabatic processes on intense Mediterranean cyclones and determine how they modify the track and intensity of cyclones and their hazardous winds and rainfall;
* Simulate and analyse changes in plausible worst case Mediterranean cyclones with climate change and quantify the changing importance of diabatic influences; and
* Synthesize the knowledge gained considering implications for forecasting and climate change mitigation and applicability to related weather systems beyond the Mediterranean, particularly subtropical cyclones.
Importantly, the atmospheric numerical model we use will have a model grid with points separated by just a few km, fine enough to be able to directly represent deep convection without the approximations that are known to misrepresent interactions between convection and larger scales. We will combine this atmospheric model with an ocean model, so-called coupling, to assess the importance of changes in the sea surface temperatures through ocean mixing. Such km-scale coupled modelling is state-of-the-art and is only now possible through advances in environmental prediction modelling. We will interrogate our model output using advanced diagnostic tools to trace the diabatic processes from their generation to weather impacts. For our climate change work we will leverage new community large-ensemble climate change simulations to drive our km-scale cyclone forecasts.
The benefits will be (1) new process-level knowledge of the importance of diabatic processes across spatial scales, (2) insight into plausible worst-case future cyclones, (3) cost-benefit analysis of km-scale coupled models for cyclone representation, (4) a synthesis that includes the implications of the findings for related weather systems across the globe, and (5) a new UK research capability for km-scale coupled modelling over the Mediterranean basin. These benefits will translate into impacts through our close collaboration with our project partners (including the Met Office) and engagement in active Mediterranean cyclones interdisciplinary research networks funded by EU COST Actions.
