This research aims to enhance the understanding of aerosol influences in urban areas, focusing on the case region of Chongqing, China. By investigating scenarios for current and future climate, this study seeks to provide insights into the interactions and impacts of aerosols on urban climate. The research questions are: How do aerosols impact the urban climate in Chongqing under the current climatic conditions? How do aerosols modify the urban climate in Chongqing under climate change conditions by the end of the 21st century? What are the uncertainties in input datasets, model configurations, and simulations of urban climate?

The Weather Research and Forecasting (WRF) model is used to evaluate the importance of aerosol effects in urban climate simulations, employing a simplified and computationally efficient approach. Two optimised WRF configurations are utilised to assess the sensitivity of the simulations. One configuration accounts for the aerosol-radiation effects, while the other incorporates the aerosol-cloud-radiation effect. A combination of in-situ observations, remote sensing data, regional climate model and global climate model outputs were used to study past, current, and future urban climate as a function of changes in aerosol concentrations.

The results demonstrate that decreasing aerosol concentrations generally result in elevated near-surface temperatures within the urban region of Chongqing, with a more pronounced impact observed when higher amounts of aerosols are reduced. Moreover, simulations that account for the influence of aerosol-cloud-radiation effects exhibit more substantial temperature changes than those that do not consider the aerosol-cloud-radiation effects. The presence of extensive and deep cloud cover amplifies the significance of aerosol-cloud-radiation effects. Partially compensating factors, including atmospheric stability, precipitation, and cloud fraction, contribute to the observed temperature changes in these simulations.

Findings indicate that climate change, rather than aerosols, is the primary driver of summer temperature increases in Chongqing's urban area. Contrary to expectations, the long-term aerosol reduction does not lead to additional regional warming and shows no statistically significant temperature change. This lack of temperature response can be attributed to the interplay between aerosols and various meteorological parameters, such as precipitation and the variation of high-level ice clouds. Both climate warming and aerosol variations lead to projected changes in surface relative humidity, liquid water content, planetary boundary layer height, surface heat fluxes, downward shortwave radiation, and net downward longwave radiation, suggesting a drier and more unstable environment.

Furthermore, this research addresses uncertainties associated with input datasets for the model, the model configurations, and the model outputs. While the optimal WRF configuration exhibits high accuracy and performance, deviations from actual local conditions highlight inherent uncertainties in the simulated results.

This study provides valuable insights into the complex interactions between aerosol concentrations, climate changes, and urban surface weather patterns. The findings enhance the understanding of aerosol effects in urban climate. In addition, the findings address uncertainties in trying to simulate these effects. An accurate representation of aerosol properties and their interactions with radiation is crucial for realistic climate simulations and for developing effective strategies for climate mitigation and adaptation.