The role of Mediterranean cyclone structure in modulating convective activity

 

Deep convection in the Mediterranean is favoured by warm sea surface temperatures and complex topography, but its occurrence is further modulated by synoptic-scale systems such as Mediterranean cyclones (MEDCs). In this study we investigate how MEDCs influence the frequency and intensity of convective environments and associated hazards. The analysis combines ERA5 reanalysis data, modelled hail and lightning probabilities, and lightning detections from the ATDNet network. A recent classification of MEDCs into nine clusters based on upper-level dynamical structure (Givon et al., 2024) provides a framework for linking cyclone types to convective activity.

For each MEDC cluster, we examine the evolution of convective environments, highlighting key differences in their spatial distribution and timing relative to the cyclone centre. In general, convective activity is most frequent northeast of the cyclone centre and within the warm sector, typically peaking before the time when the minimum central pressure is reached. Among the clusters, small and deep cyclones in the northern Mediterranean during autumn show the highest potential for severe convection, followed by weaker systems occurring in the southern Mediterranean during autumn, spring and summer.

We further identify mesoscale features within MEDCs and show that regions of warm conveyor belt ascent are more strongly linked to deep convection than cold frontal zones. This pattern is consistent across all cyclone types. Our findings advance the understanding of convective processes associated with MEDCs and offer valuable insights for improving weather forecasting and risk communication in the Mediterranean region.

Givon, Y., Hess, O., Flaounas, E., Catto, J. L., Sprenger, M., and Raveh-Rubin, S.: Process-based classification of Mediterranean cyclones using potential vorticity, Weather Clim. Dynam., 5, 133–162, https://doi.org/10.5194/wcd-5-133-2024, 2024.