The Negev Desert
The Negev (meaning "dry") makes up about 60% of the modern state of Israel (4600 sq. miles out of 8100 total). A narrow strip of it north of Beersheba gets, in good years, up to 14 inches (350 mm.) of annual rainfall, enough to grow barley. This northern Negev saw a fair amount of settlement in antiquity. South of Beersheba, though, the annual rainfall drops below 8 inches. As far as the Ramon Crater (see map), wild plants still cover at least 10% of the surface, and this is grazing desert (midbar in Hebrew, which comes from davar, an ancient term for "grazing"). South of the Ramon Crater, however, plants are found only in the wadis. Here the desert can support no flocks.
Why so little rain? First, at 31 degrees latitude the Negev is well within the belt where deserts tend to form in the Northern Hemisphere. There are two such belts, north and south. The reason is as follows: The region of the equator gets the most direct sunlight, which heats the air. "Hot air has two important qualities: it can hold enormous quantities of moisture, and it rises up into the atmosphere. So hot tropical air tends to be moist and rise into the atmosphere. As this air rises it cools, condensing the moisture and converting it to water where it falls as rain. This is why rain forests tend to occur near the equator. What goes up must come down, and gravity pulls this mass of rising air back to the ground. Tropical air typically falls at about 30 degrees latitude on either side of the equator and along the desert belt, but robbed of its moisture it is now hot and dry. The result is often persistent high pressure systems that tend to block incoming storms, or push them into other regions." (U.S. National Park Service.)
Furthermore, the great supplier of rain for the Holy Land is the Mediterranean. Yet the part of the Negev that is south of the Ramon Crater lacks this sea to its west. Instead it has the Sinai desert and, farther west, the Sahara. What's more, even when the wind blows from the northwest, most of the Negev lies too far from the sea to receive much rain.
There are spectacular examples of erosion in the Negev, but falling rain had only a small part in their making. They are rather the result of fallen rain (springs and pools), together with other factors, among them the steep decline of the central and eastern Negev toward the Syro-African Rift Valley – in other words, toward the lowest place on earth, the Dead Sea. Driving southward, the first example we encounter is the deep cut in the riverbed called Zin. (The modern Israelis gave it that Biblical name.) From the grave of David Ben Gurion, Israel's first Prime Minister, we can get a good view of this rift, as in the picture.
Scripture taken from the NEW AMERICAN STANDARD BIBLE(r), (c) Copyright 1960, 1962, 1963, 1968, 1971, 1972, 1973, 1975, 1977, 1995 by The Lockman Foundation. (www.Lockman.org)