What does the weather symbol composed of three curves mean?

As a sandstorm disaster, sand blowing does not happen in all windy places, but only in those areas with dry climate and sparse vegetation. Sand blowing mostly occurs in April-May every year. Mainly distributed in the western and northern regions, Inner Mongolia, Tibet and Xinjiang are the most serious.

Sand blowing and floating dust are two similar weather phenomena. In my work, I found that some observers were vague about the boundary between the two, which led to record deviation. Therefore, the weather forecaster on the ground should distinguish the two phenomena from the causes, the influence on visibility, color, wind power, and the time of occurrence to ensure accurate records.

relevant information

Sand blowing is caused by local or nearby dust blown by the wind, and the dust concentration in different directions is inconsistent; Most of the floating dust comes from distant dust spread by high-altitude airflow (non-local dust is blown by the wind), or from fine particles floating in the air after dust storms and sand blowing, and the dust content in all directions is relatively uniform.

The appearance of floating dust always lags behind sand blowing, that is, when floating dust appears, it must be sand blowing or sandstorm in remote or local areas. If it is local sand blowing, then the sand blowing phenomenon must have ended when floating dust is recorded.