Abstract:

Using conventional meteorological data, particulate matter monitoring and laser radar detection data, the causes and transmission characteristics of a severe sandstorm weather event in Hohhot in March 2021 were analyzed by methods of weather analysis, and air quality trajectory tracking models.The results showed that there were two peaks of pollutant concentration during this pollution process, which can be divided into two stages.From March 14 to 15, under the combined influence of an upper-level trough and a surface cold front, Hohhot experienced strong winds, blowing sand, sandstorms, and severe sandstorms.The PM_2.5 rose to 1382 mg·m^-3 at 03:00 on the 15th, and the duration of severe pollution reached 15 h.From March 16 to 18, under the weak west-ridge in the upper level and weakened surface pressure field, the near-surface diffusion conditions were relatively poor, resulting in the accumulation and return of pollutants and the prolonged duration of severe pollution.Laser radar data showed that during the daytime of March 14, there were a large number of fine particles gathered in the upper air over Hohhot.In the early morning of the 15th, the primary pollutant in this area changed from PM_2.5 to PM₁₀.At 12:00, the PM₁₀ concentration rose to 4099 mg·m^-3.On the 16th, dust returned, causing severe pollution again.On the 17th, the pollutant concentration began to decrease, and the dust weather ended at 05:00 on the 18th.Backward trajectory analysis showed that Mongolia was the main source area for this severe dust pollution.

Key words: Laser radar, Extinction coefficient, Depolarization ratio, Backward trajectory