Precipitation extremes in the Mediterranean region and associated upper-level synoptic-scale flow structures

A non-stationary analysis of daily precipitation extremes over the Mediterranean region and the associated upper-level atmospheric dynamics is presented for autumn, winter and spring. An Extreme Value Theory approach is applied to identify homogeneous areas in terms of precipitation extremes and to characterise the spatio-temporal behaviour of precipitation extremes. Results reveal a high spatial variability of extremes in the region as a whole, while the eastern Mediterranean shows a lower variability compared to the western part. The temporal variability of the estimated 5-year return levels also varies significantly across the basin especially in autumn. The synoptic-scale flow structures associated with these extreme events are then investigated. Significant upper-level flow anomalies in the form of troughs and cut-offs are found for all regions/seasons. Moreover, in many areas the associated low-level flow is directed against the local topography pointing to the relevant role of orographic lifting. Finally, significant precursor signals, 2-3 days before the events, are identified for most of the areas.