BRACING FOR DUST STORMS

The possibility of a shamal --a major sandstorm on the Arabian Peninsula--has U.S. military strategists worried, because its dusty, blinding winds could ground allied warplanes and halt troop movements for hours or even days at a time. Although it is still early in the season, the military is on alert; early signs of a shamal were detected several times in January. “Basically, it would shut down operations at any (air) base that was affected,” says Capt. Judy Dickey, a meteorologist for the 1st Tactical Fighter Wing in Saudi Arabia. Here are some facts about the shamal:

--The hot, dry wind sweeps from southern Iraq across the Saudi peninsula. Forecasters can predict its onset only three days before it arrives. --Winds travel up to 45 m.p.h. and can carve a path 60 miles long and 100 miles wide. In worst-case conditions, the storm can generate a wall of flying sand up to 14,000 feet high. -- Shamals usually arrive in March and April, but an unusually warm and dry December may mean that they’ll show up early. --Stinging sand, as fine as talcum powder, can clog air filters, overheat the engines on military vehicles and aircraft, scratch and erode rotor blades and other moving parts, and jam sensitive weaponry. Static electricity from the storms can also interfere with radio communications, making it tricky to coordinate ground forces. --Visibility in some storms is reduced to as little as a sixteenth of a mile, making accurate targeting of Iraq’s troops extremely difficult. --The dry winds are physically hard on the troops. Besides being nearly blinding, they sear the mucus passages of the eyes, nose and throat. --Even without shamal conditions, dust storms on a smaller scale are a daily problem. Any wind in such an arid, treeless terrain can fill the air with sand and dust. The Shamal wind: The wind funnels down from the northwest, starting around the Turkish-Iraqi border and ending near the northern part of the Persian Gulf. A high-pressure system forms over the Black Sea and Turkey, causing the winds to blow in a clockwise direction. The pressure funnels the warmer, dry winds downward, blowing sand and dust and creating a shamal. A low-pressure system over the Pakistan area with counterclockwise winds helps to trap the dusty flow. THE WINDS OF THE WORLD The shamal has its counterparts around the globe--seasonal winds that in one way or another shape the landscape and lives of the people they touch. Among the most famous: FOEHN: Characteristic of Central Europe, it blows upward over mountains or hills, which dries the air, then rushes downslope, growing warmer and drier as it goes. CHINOOK: A dry, warm wind that blows from a westerly direction down the east slopes of the Rockies in North America. MONSOON: In winter, a consistent cool-to-cold dry wind flowing southward across India to the Tibetan plateau. In summer, it is a warm, humid flow of air northward over India from the Indian Ocean. NOR’EASTER: A chilly or cold wind with moisture that blows with moderate to strong force from the northeast over the New England coastal regions. SANTA ANA: A foehn-type wind that blows from the deserts and plateaus of eastern California, across the southern mountain ranges, and descends--compressed and heated--through the Cajon and Santa Ana passes into Southern California. SIROCCO: A warm Mediterranean-area wind that usually sweeps northward from the hot and dry Sahara and Arabian deserts. SONORA: A warm wind that crosses Arizona from Mexico and California. ZEPHYR: A soft, gentle Mediterranean breeze, mostly from the west.