RAINFALL FIELDS IN ISRAEL AND JORDAN AND THE EFFECT OF CLOUD SEEDING ON THEM.

Abstract

Spatial correlation functions of daily rainfall were derived separately for various parts of the study area and for unseeded and seeded days. The structure of respective rainfall fields was studied by means of the relationship between the geometry of iso-correlation contours of daily rainfall and the average geometry and/or kinematics of cloud systems that produce the rainfall. Results were obtained on 1) the prevalent direction of storm movement over the study area and 2) the change in size of rainfall areas under varying conditions. Evidence is presented of an average increase of about 10 km in the dimensions of rainfall areas on seeded days. It is suggested that the size of rainfall areas is one of the fundamental factors controlling regional variations of rainfall as well as variations resulting from cloud seeding.