Study of near-surface and elevated temperature inversion layers over Ulaanbaatar city, Mongolia

Abstract

Intensifications of global warming, climate change, aridity, and human activities are causing significant changes in the regime of atmospheric phenomena and processes. The accumulation of air pollution in settlements during the cold season is a natural phenomenon driven by surface, elevated, and double temperature inversions, as well as their fluctuations. By creating a stable atmospheric state, temperature inversion significantly weakens horizontal wind speed, vertical air movement (convection), and turbulent exchange. Consequently, it is an essential meteorological phenomenon for urban planning, air quality assessment, and the accurate analysis of local microclimates. This research investigated characteristics, specifically frequency, thickness, and intensity of near-surface and elevated temperature inversions over Ulaanbaatar, utilizing radiosonde data from the 'Ulaanbaatar' station and automatic meteorological station records from 2012 to 2024. The results indicate that in Ulaanbaatar, the highest frequency of surface inversions occurs in January (reaching 68%), while elevated inversions are observed year-round with an average frequency of 49%. Notably, the simultaneous occurrence of both surface and elevated inversions in winter reaches 35%, forming a stable atmospheric layer with a total thickness of approximately 700 meters. In recent years (specifically since 2022), an increase in average air temperatures and wind speeds during the cold season has been observed. This trend has had a favorable impact on the dissipation of inversion layers and the dispersion of air pollutants. Consequently, the findings of this study possess significant theoretical and practical value for forecasting urban air quality and identifying high-risk atmospheric conditions associated with temperature inversions.