The air is a restless medium, prone to discontent, surging from place to place in wild, unruly pirouettes. Computers nowadays have allowed us to devise adventurous ways of depicting it on television, a common one being to show a broad river of arrows, sweeping along in the general direction of the flow of air. The arrow's width approximates the speed of wind; broadshafted arrows tell of gale-force winds, while slender shafts foretell a gentle breeze.
Very noticeable on Middle Eastern weather charts at present is a very broad arrow surging southwards over the sunshine symbols of Arabia. It is sufficiently prominent and common for the forecaster to give it special mention: it represents a wind called the shamal.
The shamal is not a pleasant wind. The searing heat in this part of the world is exacerbated by the fact that the average relative humidity in the afternoon is only 13 per cent, dry enough to cause vegetation to wither underneath the burning sun.
The dry, persistent, blustery shamal adds to the unpleasantness, sweeping from the northwest, day after day, down the western flank of the Mesopotamian corridor to the Persian Gulf; it throws up a powdery, choking dust that invades every pore of the human body.
Many parts of Africa and the Middle East are affected by their own brand of these very hot, dry, dusty winds known in general by the term sirocco. The wind takes its character from the desert: the temperature of the air rises as it flows across the hot surface, it gathers up dust and sand, and its humidity drops to a very low level. The name comes from the Arabic for "east wind" although not all siroccos blow from the east.
In the vicinity of Tripoli in north Africa, for example, the sirocco is known locally as the ghibli, and comes from the south. The harmattan, on the other hand, blows from the north bringing the parched air of the Sahara to the coasts of tropical west Africa north of the equator.
In Egypt, the equivalent phenomenon is called the khasmin, and it, too, comes from the deserts of Arabia: it is so hazy with fine dust that lights are sometimes required at midday. Another form of the sirocco is the leveche which originates in the North African desert and approaches Spain from the southeast.
Perhaps the most exotic of all is that mentioned by Michael Ondaatje in The English Patient, "the -------, the secret wind of the desert, whose name was erased by a king after his son died within it".