Particle-related

A dust storm is an ensemble of particles of dust or sand energetically lifted to great heights by a strong and turbulent wind (WMO, 2017). 

Fog is a suspension of very small, usually microscopic water droplets in the air, reducing visibility at the Earth’s surface (WMO, 2017). 

Haze is a suspension in the air of extremely small, dry particles invisible to the naked eye and sufficiently numerous to give the air an opalescent appearance (WMO, 2017).

A dust haze (or sand haze) is a suspension in the air of dust or small sand particles, raised from the ground prior to the time of observation by a dust storm or sandstorm. The dust storm or sandstorm may have occurred either at or near the observation site or far from it (WMO, 2025).  

Smoke is a suspension in the air of small particles produced by combustion (WMO, 2017).