Validation in urban dispersion is never easy. In such cases, there is evidence to consider: fluctuating meteorology, dynamic traffic emissions, urban complexity, uncertainty and spatial heterogeneity in both emissions and concentrations. AI can aid this process but does not eliminate…
Air pollution is hardest to understand in street canyons. Roads have buildings on both sides and emit right next to where people are standing. In these relatively narrow areas, air flow can get funnelled, held, slowed, reversed, or trapped. Consequently,…
Short-term peaks are challenging to forecast given how quickly they can arise from rapidly changing local conditions. It could be just a few minutes’ congestion, the wind shifting, a line of vehicles stopping at a junction, or a lack of…
The occurrence of pollution hotspots is seldom haphazard; instead, it arises when a confluence of factors — such as emissions intensity, street canyon geometry, wind characteristics, and exposure levels — combine in such a manner that they generate a recurring…
Urban dispersion models provide a way of calculating how pollutants travel through street and junction networks, building canyons, and across the wider urban area. They help complete missing measurement records, explore scenarios, and underpin decisions regarding monitoring network design, planning…
Urban air pollution policy commonly utilises averages. Daily means, annual objectives, and longer-term monitoring data are all important indicators of general air quality and can be used to compare trends, evaluate standards and measure broad policy changes. Averages are, however,…
Policy on air pollution in the urban environment relies on evidence. That evidence does not come from one monitor, one model or one field campaign. It is constructed over time from measurements, experiments, models, comparisons and interpretations. That is particularly…
Often, model validation is considered just one of many technical elements of the modelling exercise. A model is developed, validated against measurements, and revised as appropriate before being used to fill in conditions where measurements are not available. In the…
Street-based studies provide the essential evidence required for urban air pollution research. Yet, in a real-world environment, performing controlled experiments is almost impossible. Traffic patterns fluctuate, wind directions shift, background pollution levels change, and that exact set of circumstances never…
Urban dispersion research has never been the business of a single viewpoint. To truly comprehend how air and pollution travel through the streets of a city, relying on observation alone or numerical models alone is insufficient. It takes a combination…