Sand And Dust Storm

Sand and Dust Storm

Parts of the world experience sand and dust storms, the Sahara Desert are an obvious example. But changing climate, increasing cultivation and overgrazing are increasing the incidence of sand and dust storms worldwide. Many cities, notably Beijing, China are regularly blanketed by choking dust that reduces visibility, clogs machinery, contaminates food and even kills.

There are five ingredients essential to the development of sand and dust storms:-

1. A source of fine dust or sand particles that can be lifted and transported,

2. Winds of sufficient force and velocity in a direction that will raise and carry the particles,

3. Weather conditions that can form convection cells of sufficient energy to develop the winds,

4. Landform features that help concentrate the force of the wind, and

5. Exposed soil surfaces susceptible to wind erosion, such as in deserts and over-cropped and disturbed semi-arid lands.

Characteristics of Dust Storms

A dust storm usually arises suddenly in the form of an advancing dust wall that may be many miles long and a thousand yards (1 km) or so deep. Ahead of the dust wall the air is very hot and the wind is light.

The US weather watches classify dust storms according to visibility:-

1. If blowing dust reduces visibility to between 5/8 and 5/16 mile (1.0 and 0.5 km), a dust storm is reported.

2. If the visibility is reduced to below 5/16 mile (500 m), it is reported as severe.

Dust storm winds can also be associated with thunderstorm outflows and gust fronts. Vertical downdrafts of chilled air during thunderstorms may locally strike the ground with velocities of 25 to 50 miles per hour (40 – 80 km/h). Under such conditions, fine particles may also be swept upward hundreds or thousands of feet into the air. The average height of a dust storm is 3,000 to 6,000 feet (900 – 1800m) and stronger storms have dust to 8,000 – 10,000 feet (2400- 3000 m). Haze and dust from extreme storms have been documented as high as 35,000 to 40,000 feet (10,700 – 12,200 m). While these are often shorter, lived than wind-forced dust storms, they can be quite intense, with an impressive leading edge, called a dust wall. Dust storms on Mars can reach 130,000 feet (40 km) high.

North Africa is a source of dust that is transported to Southern Europe, and the Sahara region is the main global source of wind- blown dust. About 10 million tons of dust particles can be transported and brought to Britain from the Sahara Desert during a Single dust storm. Arid and semi-arid regions around the Arabian Sea are other significant sources of dust. India, Pakistan, Iran and the Arabian Peninsula Contribute to Arabian Sea dust deposition and dust from China contributes to sediment in the Pacific Ocean. Storms regularly occur in the arid and semi-arid regions of the Earth, particularly in subtropical latitudes. Sand and dust storms are natural events that have occurred throughout Earth`s history. The geological record shows that changes in the growth and decline of desert sand surfaces over time are characterized by evidence of sand and dust storms, making the storms useful indicators of climate during past eras.

In recent times the action of humans has greatly increased the desert sand surface area through poor land management, which has destabilized the desert margins. Such actions include overgrazing vegetation beyond its carrying capacity, gathering firewood for fuel and clearing to plant crops. Corresponding to these areas of accelerated desertification is an increase in the severity and frequency of the many major sand- dust storms throughout several regions of the world. As in past geological eras, they could be considered indicators of current climate change.

 

Precautions to take during a Sand and Dust Storm:-

1. During threatening weather, listen for dust storm warnings on radio or television.

2. Dust can cause respiratory failure, so stay indoors with windows and doors closed.

3. If you are driving pull over as far as possible when you see dust blowing across or approaching a roadway, stop and drivers might try to follow you and run into you.

4. If there is nowhere you can pull over, then proceed at a safe speed, turn on your lights and sound your horn occasionally. Use the painted centre line to help guide you look for a safe place to pull off the roadway. Never stop on the road.