Abstract:

On the basis of data from 14 radiosonde stations and their corresponding surface meteorological automatic observation stations in Xinjiang, China, from 2010 to 2019, the temporal and spatial distribution characteristics of air mixing depth, ventilation rate, mean wind speed in boundary layer, and air self-cleaning ability index in the past 10 years were analyzed. The correlation between meteorological parameters and air quality was discussed based on the air quality index (AQI) data of 10 air quality monitoring stations in Xinjiang from 2015 to 2019. Results show that (1) the monthly distributions of the maximum mixing depth, the ventilation rate, the mean wind speed in the boundary layer, and the index of atmospheric self-cleaning ability had an inverted “V” shape, thereby indicating that the atmospheric diffusion ability of Xinjiang is strong in summer and weak in winter. (2) With regard to the spatial distribution of atmospheric diffusion conditions in Xinjiang, two different diffusion areas are found in southern and northern Xinjiang due to different topographies. The atmospheric diffusion conditions in southern Xinjiang are generally better than those in northern Xinjiang. Whether in winter or summer, southern Xinjiang has greater self-cleaning ability, ventilation capacity, and mixing depth than northern Xinjiang does, but the mean wind speed in the boundary layer is the same in southern and northern Xinjiang. This condition is mainly due to the great difference of non-adiabatic heating on the ground caused by different sunshine duration and intensity. (3) An analysis of the correlation between the above parameters and AQI shows that the atmospheric diffusion conditions of stations in northern Xinjiang are significantly negatively correlated with AQI except Altay station, and they all passed the 0.01 confidence test. The conditions are not consistent in southern Xinjiang; only Hotan station passed the 0.01 confidence test, thus indicating a significantly positive correlation, which is the opposite of northern stations in Xinjiang. This result occurred because the causes of air pollution in northern and southern Xinjiang are different. The main pollution sources in southern Xinjiang during spring are sand and dust, especially at Hotan statio station, where sand and dust increase under good atmospheric diffusion conditions, resulting in poor air quality. In northern Xinjiang, pollution is mostly due to the stable atmospheric stratification, which results in failed coal smoke emission from urban factories. The strong atmospheric diffusion ability will help the dilution and diffusion of pollutants and improve the air quality.

Key words: atmospheric diffusion conditions, self-cleaning ability index, ventilation, mixing depth