## 4 Conclusions  
By combining simulation and monitoring data and comparing the feasibility of using a combination of Geographic Information Systems (GIS) and Computational Fluid Dynamics (CFD, e.g., Fluent), the modeling time can be significantly shortened, and the research efficiency can be improved. Digital terrain surface simulation can be conducted using limited terrain elevation data. Based on this, in-depth research can be carried out to enhance accuracy, which can be used to analyze the fluid dynamics in more complex study areas. The study area is located at the northwest opening of a southeast-northwest oriented canyon. The terrain is characterized by higher elevations in the southeast and lower in the northwest, which easily leads to changes in the wind field. Through the coupling results of GIS and CFD, it is found that when there are northwesterly winds, a vortex phenomenon tends to occur on the leeward side of the mountain range. Due to the blocking effect of the mountain range, the wind speed on the southern side of the mountain range is generally lower. When the air pressure field on both sides of the canyon shows a high-in-the-south and low-in-the-north situation, under the action of the air-pressure gradient force and the \"narrow-tube effect\" on the leeward side, vortices with different wind speeds appear at the two ends of the mountain range on the windward side. The wind speed on the leeward side gradually decreases, and the frequency of calm winds increases. The study area is located in a basin surrounded by mountains on three sides, resulting in poor air circulation and slow pollutant dispersion. In terms of temporal and spatial distribution, the air quality index in the study area shows that the air quality in the south is better than that in the north. In winter, the prevailing northwest wind drives atmospheric particulate pollutants to move southeastward. Blocked by the mountain range on the right, the pollutants are deposited in the basin. Generally, the concentration of air pollutants is lower in the south than in the north. Geographic Information Systems (GIS) offer detailed geographical data, including terrain, landform, and meteorological information, while Computational Fluid Dynamics (CFD) can simulate the flow characteristics of air currents under complex terrains. By coupling GIS and CFD, we can account for the influence of terrain on air currents and pollutant diffusion, enabling precise simulation of pollutant dispersion. This integrated approach not only enhances the accuracy of pollutant dispersion modeling but also allows for a more accurate assessment of wind energy resource distribution and potential, thereby improving the overall accuracy of air quality assessments. Based on our research findings, we propose several targeted measures to improve air quality in Urumqi:  
Figure 14: NO\({}_{2}\) monitoring station data. Strengthen traffic management and industrial emission control: High-emission areas in the city center should be prioritized for traffic management and industrial pollution control. Implementing traffic restriction measures, such as congestion charges or vehicle bans during peak pollution periods, can significantly reduce vehicular emissions. Additionally, promoting the use of clean energy, such as natural gas or electric vehicles, can help mitigate pollution from transportation sources. Enhance suburban emission monitoring and treatment: While urban areas are a primary focus, it is equally important to monitor and treat emission sources in the suburbs. This includes stricter regulations and enforcement for industrial facilities located outside the city center, ensuring that they meet emission standards and employ effective pollution control technologies. Establish an air quality early-warning mechanism: To protect public health, an air quality early-warning system should be established. This system would promptly release air quality information to the public, especially during periods of high pollution.