The Atmospheric Dispersion Model System

The text on this page is taken from an equivalent page of the IEHIAS-project.

The Atmospheric Dispersion Model System (ADMS-Urban) is produced by [www.cerc.co.uk CERC] and uses an up-to-date understanding of the atmospheric boundary. This is described by boundary layer depth and the Monin-Obukhov length, rather than by the Pasquill stability categories.

Purpose

ADMS-Urban can be used to predict air pollution concentrations from a range of sources.

Boundaries

• Field of model: Outdoor Air
• Spatial: Output can be defined as specified point locations (e.g. addresses, postcodes) or by using intelligent griding as contour plots
• Temporal: Pollution concentrations can be calculated for averaging times ranging from seconds up to years
• Pollutants covered: all priority pollutants + metals
• Source types of emissions / sectors
• Moduls: Street canyons, complex terrain, buildings
• Chemistry information:
  1. NO_x-NO₂ chemistry model which includes reactions with ozone and hydrocarbons;
  2. Trajectory model - a simple Lagrangrian Trajectroy model can be used to calculate background concentrations for the air approaching the main modelling area
  3. Sulphate chemistry

Input

Source parameters include:

• source location data,
• road widths and canyon heights for road sources,
• stack heights, diameters, exit velocities, etc., for industrial sources,
• grid dimensions for aggregated emissions data.

Emission profiles can be defined to take into account the diurnal variation in emissions

Meteorological data requirements include temperature (°C), wind speed (m/s), wind direction (°), precipitation (mm), cloud cover (oktas), relative humidity (%), boundary layer height (m), and surface sensible heat flux (W/m²).

Traffic flow, ADMS-Urban can automatically recalculate traffic flows into emission rates, or this can be done alternatively by the Emissions Inventory Toolkit (EMIT)

Background concentrations (optional)

Output

Pollution concentrations at user defined averaging times (seconds up to years). ADMS-Urban can calculate percentiles, the number of exceedences of threshold concentrations and rolling averages.

Output files can be read straight into ArcGIS to create contour plots.

Output files are in text files and can be easily read into Excel.

Description of processes modelled and of technical details

Commercial model - information on cost at CERC-website.

Operating system: XP, Vista

Minimum computer requirements: Pentium 1.5Hz, RAM 1 GB

Links with other software: ArcGIS, Surfer, MapInfo

Canned model - cannot be modified