Study of climate regime and near-surface temperature inversion of Dalanzadgad city, South Mongolia

Даланзадгад орчмын уур амьсгалын горим, газрын гадарга орчмын температурын инверсийн судалгаа

Abstract

Under the combined effect of global warming, dryness and human activities, the characteristics of climatic phenomena and elements are changing significantly, and their impact on the environment, society, and economy is increasing. The inversion of surface temperature and its changes can be mentioned here, which is a natural phenomenon that accumulates air pollution for a long time in the cold season. By creating a stable atmospheric condition, the temperature inversion significantly weakens the horizontal wind speed, vertical air movement or convection, as well as the intensity of vertical air mixing or turbulent exchange. Therefore, it is one of the climatic phenomena that should be studied, which is necessary to choose the place of wintering and springing and to assess the microclimate of the region accurately. For the scope of this research, the regime and changes of climate parameters that affect the near-surface temperature inversion layer have been determined in Dalanzadgad, Umnogov Province, as well as has been tried to determine the regime and its characteristics of the surface temperature inversion parameters over Dalanzadgad that occur in the cold season. Then, the relationships between the temperature inversion and the air quality are studied. The average monthly air temperature values for 1991-2020 exceeded the norm of 1961-1990 by 0.4-2.3°C, which is a condition for weakening the temperature inversion parameters. However, the number of windless cases reach 23% of total measurements in winter, 11% in spring, 14% in summer, and 17-18% in autumn, which will be a favourable condition for the formation and intensification of surface temperature inversion. According to radiosonde measurements, the near-surface temperature inversion with an intensity of 4.9-7.1°C and a thickness of 190-240 meters is observed in Dalanzadgad during the cold season on 22-26 days. The correlation coefficient for the intensity of the temperature inversion is r=0.42-0.62, p<0.0001 with sulfur dioxide (SO₂), r=0.31-0.52, p<0.0001 with nitrogen dioxide (NO₂), r=0.62-0.69, p<0.0001 with PM_2.5 concentrations, and r=0.69-0.75, p<0.0001 with PM₁₀ concentrations, it can be concluded that it has a moderate to strong correlation on air pollution and particle accumulation.