Green, D. N.

The relationship between Mediterranean precipitation and North Atlantic and European sea level pressure fields has been studied using statistical techniques to investigate the variability within the data. A principal component analysis shows the major winter precipitation variability is described by a see-saw fluctuation between the Western and Eastern Mediterranean. The pressure-precipitation relationships indicate that a highly variable, pressure region situated to the south of Britain dominates this major precipitation pattern. The large-scale pressure fields which facilitate the precipitation patterns have been isolated using a canonical correlation analysis. Although the well-known major pressure centres of action in the North Atlantic are important, pressure changes in the east are found to also control the transport of moisture across the Mediterranean to a large degree, as the presence of a large high over Kazakhstan causes meridonial flow and impedes the passage of moisture across the Mediterranean. The pressure-precipitation relationships are found to be very consistent over multi-decadal,seasonal, monthly and daily time-scales with trajectory analysis confirming many of the features of the average seasonal pressure charts. This steadiness and regularity indicates that the Mediterranean precipitation teleconnection is a robust phenomenon that is affected by large-scale pressure changes to both the east and west.