Radar analysis of cloud systems and their rainfall yield in Israel

This study documents the climatological occurrence of rainfall from different types of rain cloud systems over Israel and the adjacent seas. The rain cloud types are: (a) cold front; (b) cloud systems that develop in the cold sectors of cyclones; and (c) cloudiness of the cyclone center (vortex). The cloud systems within the cold sector include: (a) convection lines; (b) open Benard cells and unorganized cells; (c) the coastal front; and (d) cloud streets. While the warm front rain yield is negligible, the Red Sea trough adds about 5% to the total precipitation in the Mediterranean climate region of the country. The main rainfall yield contribution in the north of the country comes from cold fronts and vortices, while the southern part is dominated by less dynamically and more air-mass-convection-controlled rain cloud systems, such as Benard cells and coastal fronts. Analysis of the cloud pattern on a monthly basis reveals that the cold front is more active during November-December, with the climax of the coastal front in December, and the main vortex activity starts in January. We checked rainy/dry year variations and found that during rainy years, the vortex rain contribution is larger than that of the cold front. The coastal front also contributes more rain during wet years and tends to follow a more southerly route. In dry years, the proportion of vortex/cold front is reversed, and the coastal front rain yield is meager and has a more northerly route.