Circulation indices over the Mediterranean and Europe and their relationship with rainfall conditions across the Mediterranean

Circulation types were identified by means of zonal and meridional indices calculated separately over ten different regions of 20 degrees x 20 degrees over the Mediterranean and Europe. Seasonal and annual rainfall totals in four stations Lisbon, Luqa (Malta), Athens and Jerusalem, were compared with circulation types for the period 1873-1991. Correlation coefficients of circulation indices with precipitation, for each station in each season were calculated and mapped. An oscillation in the meridional index during the winter and the spring, between the western and eastern Mediterranean, was detected. Time series analysis of the circulation indices demonstrates a significant reduction in zonality and an increase in meridionality mainly in spring and in summer, over most of the study area.