 The Sirocco ("Gibleh" or "Ghibli"), a hot desert wind, blows clouds of fine sand, which reduces visibility to a few yards and coats eyes, lungs, machinery, food and equipment; motor vehicles and aircraft need special oil filters and the barren ground means that water and food as well as military stores have to be transported from outside.The area between Sollum, Maddalena, Bir el Gubi and Tobruk is larger than East Anglia and except near the coast, has a hard, flat and open surface, easy for desert-worthy vehicles to cross, except after rain.From Bardia west to El Adem the ground undulates with several east–west ridges, the north-facing sides usually being escarpments only passable by vehicles in a few places.