The best combination for dust is windy conditions, dry conditions and a dry climate. A dry climate has a significant amount of exposed earth. There is not much vegetation and moisture to hold the dirt in place. Dry conditions allows the wind to better erode the dirt and makes the dirt lighter and thus easier for the wind to loft. Windy conditions allows the dust to be lofted into the air. The size of the dust will depend on wind speed and the type of earth exposed to the wind. Very fine dust is typical of lofted materials since the wind is strong enough to overcome gravity bringing it back down to the ground. Larger particles of dust and sand require a stronger wind speed to keep them aloft. Sand storm: These can occur in arid environments in which a long fetch of wind is able to pick up sand and dust particles and blow them downwind. These storms can cut visibility to near zero and get sand and dust into everything. Blowing dust: This occurs in a arid or semi-arid region in which strong winds pick up dust particles. These events are common when the winds are strong behind a dryline passage. Blowing dust can also occur anytime the wind is strong. In moist climates, blowing dust is not as common since the soil moisture and plants prevent the wind from lofting dust particles. On visible satellite, blowing dust looks like thin wispy gray clouds. Look for dust in the dry sector of a mid-latitude cyclone such as behind a dryline. Examples will be posted below as they come up. |