As shown above, an afternoon sandstorm engulfs Kuwait’s Ali Al Salim Airbase on March 25, 2011. The encampment was battered by gusty winds (up to 70 mph or 112 kmh) carrying sand and dust for about eight hours, making it difficult to walk, breathe or see.  Photographer: Rob Sheridan

This soldier is staggering through the gusts, well before sunset when visibility should be excellent. He’s holding a cloth to his face to facilitate breathing and minimize the damage to his eyes. Gusting winds are nearly ripping apart the heavy-duty tent.

Sandstorms are typically triggered by cool surface gusts out-flowing from thunderstorms or by cold dry surface air masses in rapid motion. The forces that suspend the heavy dust and sand are a combination of saltation and static repulsion. Strong surface winds passing over fine loose particles of sand and dust cause them to begin vibrating or “saltating“. If winds are strong enough, the particles will repeatedly strike the ground, loosening others, and eventually become suspended in the air and moving with the wind. The density of the resulting air-particle suspension depends on the wind speed and particle mass. Friction between individual particles generates a static charge — the suspended particles becoming negative relative to the ground. This charge acts to increase the suspension density. Convection currents generated when the cold air masses move over hot ground further fuels the density of the suspension and contributes significantly to the height of sandstorms, which can reach an altitude of approximately two miles (a little over three km).Sandstorm

Sandstorms possess an enormous amount of energy and can move huge volumes of sand and dust, changing local topographies in hours. Prolonged exposure to the finely suspended dusts, mostly finely eroded silicon dioxide, can lead to silicosis and corneal injury in humans and other animals. Sandstorms increase in frequency and severity in semiarid and arid climates whenever dry-land farming techniques are widely adopted. Large tracks of central North America were beleaguered by sandstorms in the 1930s — the U.S. southern plains were referred to as the Dustbowl. North Africa has been dealing with similar problems in recent decades.

via epod