Definition

Clouds of blowing sand or dust.

Description

Common in arid or semi-arid areas, particularly the Sahara and the Arabian peninsula, a sand storm is created by:

• An advancing Gust Front
  • ahead of a Cumulonimbus (Cb) cloud (typical in the Sahara);
  • along a cold front where cool air passing over hot ground creates instability in the air above (typical in the US mid-west).
• Strong winds: when the wind speed increases above the threshold speed needed to lift and transport surface particles.

An advancing sand storm associated with a gust front is a spectacular sight and looks like an advancing wall of swirling sand. The height of this wall can be 1 nm or more; in situations where there is significant atmospheric instability, dust can reach as high as 20,000 feet.

Sand storms move material by three mechanisms: