Simulation study of low-level disturbances affecting near surface inversion events in Urumqi.

With accelerated urbanization, temperature inversion phenomena are becoming more prominent in urban atmospheric environments, playing a very important role in air quality and public health. Despite the widespread literature on the formation and longevity of inversions, little is understood about the measures to mitigate them. Filling this knowledge gap, this work examines the impact of low-level artificial perturbations on near-surface inversions through the use of numerical modeling. The case is selected from an inversion event in Urumqi at 08:00 on 19 January 2023. Numerical simulations were done using the Fluent fluid dynamics model and the Advanced Regional Prediction System (ARPS) model. The results indicate that the application of low-level perturbations can destabilize inversion layers, cause vertical mixing, and promote atmospheric instability. Comparative experiments with the two models confirm that external perturbations disrupt stability stratification, enabling exchange and dispersion of air and pollutants. The simulations also indicate that increased inflow wind speeds facilitate atmospheric turbulence, leading to increased instability and improved air quality. Specifically, the thickness of the inversion layer decreased by approximately 40% after two hours of disturbance, and after three hours the inversion was practically eliminated. The Fluent model indicates localized flow field changes, while the ARPS model simulates the large-scale atmospheric response. The two-model approach provides an integrated picture of the processes for the breakdown of the inversion layer. The results provide new insight into the control of urban air pollution, with the implication that certain artificial disturbances can be employed as an effective method for the mitigation of temperature inversions in highly polluted cities.