Ammonia (NH₃) is a major source of pollution in the air. As such, there have been increasing efforts to measure the atmospheric abundance of NH₃ and its spatial and temporal variability. In this study, long-term measurements of NH₃ over Toronto, Canada, derived from multiscale datasets are examined. These NH₃ datasets were compared to each other and to a model to better understand NH₃ variability and to assess model performance.