The urban environment plays a unique and critical role in the Earth system. Air pollutants can interact with urban meteorology and emissions in a complex way, which has not been fully understood. Urban areas are also the most populated regions where air pollution can exert significant adverse impacts on human health, with potential environmental justice issues. Moreover, different urban regions may have their own characteristics for air pollution and interaction with climate. This session calls for modelling and observational studies to improve the understanding and quantification of (1) urban emissions and interaction with different urban environments, (2) atmospheric chemistry processes affected by urban meteorology and feedback to urban climate/weather, (3) urban air pollution interaction with rural emissions and long-range transport, (4) cross-scale urban chemistry-meteorology interactions, (5) impacts of urban air pollution and extremes on public health and environmental justice, (6) effective solutions (including the Nature Based Solutions (NBS)) to mitigate adverse impacts from urban air pollution and extremes (e.g., urban heatwaves and floods).