Dust Storms

Introduction

Dust storms occur when sustained high winds blow near Earth’s surface in arid regions, pick up large quantities of fine sand or dust, and transport the materials over great distances. More than 40% of the world’s land surface is arid, either already desert land or in the process of desertification. These desert margins undergoing desertification are prone to dust storms. Human activities—particularly mismanagement of land use in marginal arid regions—and climate change that is causing desert areas to get even drier are contributing to an increase in dust storms. Dust storms arise most frequently in Central Asia, North America, Africa, and Australia.

Airborne particles in dust storms are a health hazard and can cause considerable damage because of their abrasive effect on objects in the storm’s path. When dust storms pass over industrial areas, emissions from the combustion of fossil fuels can be incorporated in the storm, causing even more serious health hazards.

Historical Background and Scientific Foundations

Core samples taken from ocean floors and studies of glaciers indicate that dust storms have occurred for at least 70 million years. The term “dust storm” also includes sand storms, the difference being the size of the soil particles involved. Sand particles are about 0.02 in (0.5 mm) in diameter, while dust particles are smaller. The size of the particles transported and the wind speed determine the character of a dust storm.

Blown sand generally reaches a height up to about 49 ft (15 m) in winds of 10 mph (16 km/h). Heavy sand particles tend only to creep along the surface moving sand dunes from one location to another. At higher wind speeds, sand particles are lifted and then bounce along the surface, a process called saltation. This process can loosen finer particles and trigger a more extensive dust storm. Very fine dust particles can be lifted by turbulent air hundreds or thousands of miles into the atmosphere and be carried many thousands of miles with the prevailing winds. Dust from extreme storms has been documented as high as 35,000 ft (10,668 m). Fine clay dust particles that are extremely small (0.00004 in/0.001 mm in size) can remain in the atmosphere for years.

Dust clouds prevent solar radiation from reaching the ground temporarily, causing a cooling effect at Earth’s surface. However, dust clouds also absorb solar radiation thereby heating the cloud itself. Dust storms are most likely to occur in the spring when weather systems are most turbulent. Once a dust storm begins, the dust cloud can travel thousands of miles across the globe. Dust from the Sahara region of Africa is the source of much of the wind-blown dust around the world, although some dust storms that originated on the Mongolian-China border have reached the United States and Canada.

Impacts and Issues

Dust from the Sahara region can travel across the Atlantic Ocean. The change in solar heating associated with a dust cloud temporarily alters Earth’s climate; cooling at the surface can occur far downwind from the dust cloud. The U.S. National Aeronautics and Space Administration Goddard Institute of Space Studies has researched the effect of major dust storms on climate. The cooling effect from one major Arabian dust storm was observed to extend to regions from northern Asia to the Pacific and North America. The average surface temperature was reduced by 1.8°F (1°C).

The relationship between climate change and dust storms continues to be a focus of research. Recent stud-

WORDS TO KNOW

DESERT: A land area so dry that little or no plant or animal life can survive.

DESERTIFICATION: Transformation of arid or semiarid productive land into desert.

SALTATION: The intermittent, leaping movement of small particles due to the force of wind or running water.

ies using data from the Advanced Very High Resolution Radiometer on U.S. National Oceanic and Atmospheric Administration (NOAA) polar-orbiting satellites indicate there is a correlation between increased dust storm activity in the Sahara region of North Africa and a reduction of Atlantic Ocean hurricanes. Dust storms and sand storms are seen easily by instruments on NOAA satellites. For the past 25 years, NOAA has used the data gathered by these satellites to monitor the sources of dust storms and sandstorms and track their movements.

Dust storms are a common occurrence on Mars; clouds of dust have been observed to cover almost the entire surface of the planet for weeks at a time. Although Venus and Saturn’s largest moon, Titan, also have significant atmospheres, neither is known to experience dust storms.

IN CONTEXT: BLACK BLIZZARDS

Beginning around the 1880s, pioneer settlers started to extensively farm the former short grasslands of the Great Plains with improper agricultural practices for such a semi-arid climatic environment. With the removal of these stable grasses, a sustained period of drought and perpetually strong and destructive wind and dust storms (often called Black Blizzards) caused severe soil erosion, removal of topsoil, and nutrient leaching in the latter half of the 1930s in many areas of eastern Colorado, western Kansas, eastern New Mexico, the Oklahoma Panhandle, and western Texas. As conditions wors-ened, any soil conservation measures that had been previously used were drastically cut or eliminated in order to reduce costs. In order to make more money, farmers often expanded onto poorer lands that caused even more vulnerability to loss of soil moisture, depletion of soil nutrients, wind erosion, and other environmental problems.

See Also Desertification; Deserts; Drought; Land use; Overgrazing

BIBLIOGRAPHY

Web Sites

NOAA (National Oceanic and Atmospheric Administration) Magazine. “Dust Storms, Sand Storms and Related NOAA Activities in the Middle East.” April 7, 2003. http://www.magazine.noaa.gov/stories/mag86.htm (accessed March 29, 2008).

United Nations Convention to Combat Desertification. “Dust and Sandstorms from the World’s Drylands.”http://www.unccd.int/publicinfo/duststorms/menu.php (accessed March 29, 2008).

U.S. Geological Survey. “Desertification.” http://pubs.usgs.gov/gip/deserts/desertification/ (accessed March 29, 2008).