Atmospheric circulation types and floods' occurrence; A thorough analysis over Greece

Floods have a direct impact on the society and the environment, causing human losses, affecting individual incomes and national economic activity including infrastructure damages. Atmospheric circulation is strongly related to both mean and extreme climate, with the latter being the driving force of adverse phenomena, such as inundations. The overarching goal of the research is the identification of those atmospheric circulation patterns that are associated with catastrophic flood events over Greece. An updated atmospheric classification scheme consisted of 12 circulation types (5 anticyclonic and 7 cyclonic) is implemented to detect and highlight the flood-dominant circulation types over the domain of interest. It is established that for a 7-year period (from 2012 to 2018), where reliable flood inventories are available as a derivative of the European Union (EU) Flood Directive implementation process, the dominant circulation type is the cyclonic type C with its center to be located over the Cyclades area. The study also reveals that during the most severe floods, the prevailing cyclonic types are substantially deeper than their mean anomaly field. Finally, out of the 14 River Basin Districts of Greece, Thrace (EL14) is the more flood prone area, while Eastern Macedonia (EL11) is far less flood affected. The introduced Floods' Frequency Vulnerability index (FFVI) showed that in the case of significant floods, Western Peloponnese (EL01) and Epirus (EL05) are the most vulnerable River Basin Districts. The proposed methodology of coupling circulation types with flood occurrences can be applied in all EU Member-States and set the base of effective floods' prediction mechanisms at River Basin Districts scales.