On the analysis of the temporal precipitation distribution over Greece using the Precipitation Concentration Index (PCI): annual, seasonal, monthly analysis and association with the atmospheric circulation

The investigation and analysis of precipitation concentration on an annual and seasonal basis, over Greece, motivated the present study. To achieve this objective, the Precipitation Concentration Index (PCI) was implemented for various stations over the domain of interest, for a 43-year period starting from 1958 up to 2000. On an annual basis, the results showed that northern Greece is characterized by a moderate precipitation concentration while moving to the southern parts of the country, PCI values increase. The stations over the western and central Greece present a moderate concentrated distribution, while in the Cyclades areas and southeastern Aegean Sea, precipitation amounts are concentrated in only a few months of the year with a prolonged dry period. In winter and spring, the whole Greece is characterized, in general, by a moderate concentrated distribution, and the seasonal amounts are relatively even distributed among the three season's months. Contrarily, in summer, the results are less coherent and the index values are much higher. Finally in autumn, according to the PCI values, continental Greece is characterized by moderate concentrated distribution while the islands of the Aegean Sea by a high concentrated distribution. Overall, Greece seems to be shifting during the time period under study to a more concentrated precipitation contribution especially regarding the annual, winter, spring, and autumn totals. This change can be partially related to the changes of the atmospheric circulation over the country due to the decrease of the frequency of the wettest circulation types on an annual basis.