The Relationship of Rainfall Patterns in the Galilee, Israel, to Regional Circulation Patterns.

The spatial distribution of rainfall in the Galilee, Israel, is attributed to the roles of different mechanisms of production, intensification and distribution. The relative importance of explanatory mechanisms changed from 1931 -60 to 1951-80. A decrease in the role of distance from the main storm track, and a shift of isohyets to a more N-S direction, is attributed to a shift of mesoscale circulation toward more meridionality. Cloud-seeding operations since the 1960s may also be a contributory cause. The peak of the rainfall season occurred later in the second period. The seasonal pattern of the roles of the different mechanisms is seen in individual years as well. Average rainfall over the region is shown to decrease when altitude is the most important factor, or when the importance of longitude decreases. The study of monthly mean sea level pressure over Europe, the Mediterranean, and the Middle East, showed that the patterns in 1961-80 were similar to those in 1931 -60, but the magnitudes were different. The major change in the seasonal regime of pressure between the two periods was a retardation in the building of high pressure over western Soviet Union in the second period. An anomaly center in both sea level pressure and 700 mb height fields over the eastern Mediterranean was the most prominent feature. Rainfall in the Galilee varied from dry to wet according to the signs of these centers.