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World leading software for urban air quality management

Model options

One of the most important advanced modules in ADMS-Urban is the chemistry module. The following options are available:

  • NOxNO2 chemistry
  • The Trajectory model
  • Sulphate chemistry

Other advanced modules are:

  • Street canyons
  • Complex terrain
  • Buildings

These modules are based on the latest understanding of the way these features affect the movement of airflow around the sources, and all have been shown to have considerable affect on observed concentrations.

Chemistry module

In many urban areas, the dominant pollution source is road traffic, and the pollutants usually of major interest are NOx, O3, PM10 and PM2.5.

The ADMS-Urban models NOx chemistry using the 8 reaction Generic Reaction Set (Venkatram et al., 1994) that includes reactions with ozone and hydrocarbons.

The NOx chemical reactions take place over a relatively short time period and in order to get accurate predictions of NO2 concentrations, NOx chemistry should be taken into account. The Generic Reaction Set also predicts changes in ozone concentrations.

The Trajectory model

A simple Lagrangian Trajectory Model is used to calculate background concentrations for the air approaching the main modelling area. This model includes the effects of emissions, chemistry, deposition and ozone entrainment.

By nesting the main model domain within a larger domain, such as a large urban conurbation, the Trajectory Model calculates a spatially varying background ambient concentration that takes into account the chemical reactions and processes occurring over the larger domain.

Sulphate chemistry

The reactions between SO2 and other compounds in the air to produce particulates are based on those used in the EMEP model (Tsyro, 2001).

These reactions have a significant effect on the concentrations of particulates in areas where there are a large number of industrial sources emitting SO2 or downwind from a large emitter of SO2.

Street canyons

'Street canyons' are defined as the deep, narrow, valley-like spaces created when a road is enclosed by tall buildings on both sides. High pollution levels are often observed in street canyons. ADMS-Urban includes two modules for modelling street canyons.

The basic street canyon module is based on the Danish Operational Street Pollution Model (OSPM, Hertel and Berkowicz, 1990, Hertel et al., 1990).

The advanced street canyon module (Hood et al., 2014) can be used if a more detailed model of the street canyon is required. It differs from the basic module in the following ways:

  • The model has been formulated to consider a wider range of canyon geometries, including the effects of tall canyons and of canyon asymmetry;
  • The concentrations predicted by the model vary with height within the canyon;
  • Emissions may be restricted to a subset of the canyon width so that they may be specified only on road lanes and not on pedestrian areas;
  • There is the option to include consideration of 'network' effects, where pollutants reaching the end of one street canyon can pass into a connected canyon; and
  • Concentrations both inside and outside a particular street canyon are affected when running this model option.

Complex terrain

This module is based on FLOWSTAR advanced airflow model which calculates the change in mean flow and turbulence due to terrain and changes in surface roughness (land use).


Users can include the effect of up to 25 dominant buildings on point source emissions. ADMS-Urban creates an effective building for each point source from the user-defined buildings and models the re-circulating flow in the lee of the building, the cavity region, as well as the building main wake.

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