ADMS-Urban

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:

• NO_x – NO₂ 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

NO_x – NO₂ chemistry

In ADMS-Urban there are two ways to model NO_x chemistry. The first is using a simple correlation scheme (Derwent and Middleton, 1996) but the recommended option is to use the 8 reaction Generic Reaction Set (Venkatram et al., 1994) that includes reactions with ozone and hydrocarbons.

In most urban areas, the dominant pollution source is road traffic, and the pollutants usually of major interest are NO_x and PM₁₀. The NO_x chemical reactions take place over a relatively short time period and in order to get accurate predictions of NO₂ concentrations, NO_x chemistry should be taken into account. The Generic Reaction Set predicts changes in ozone concentrations that are also of interest.

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

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

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).

Buildings

Users can include the effect of up to 10 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. The complex terrain and buildings modules cannot be used concurrently.