Model Name




Model description


The URBAIR model has been developed from the POLARIS, a Gaussian model previously developed by the GEMAC team [1]. This model is significantly different from traditional Gaussian dispersion models, because its dispersion parameters have a continuous variation with the atmospheric stability. The model is suitable to be used for distances up to about 10 km from the source. The model is a steady state atmospheric dispersion model, based on boundary layer scaling parameters, such as the Monin–Obukhov Length instead of relying on Pasquill-Guifford stability classification. A preprocessor calculates the meteorological parameters needed by the dispersion model, such as atmospheric turbulence characteristics, mixing heights, friction velocity, Monin-Obukov length and surface heat flux.

To characterize the meteorological conditions within the simulation domain, the model requires meteorological information driven by surface measurements and upper air soundings databases or, optionally, data from on-site instrument towers. Instead vertical meteorological profiles can be obtained from mesoscale meteorological models.

URBAIR requires also the characterization of topography, land-use, buildings and the emissions of anthropogenic sources, which can be provided by inventories. Traffic emissions can be estimated by the Transport Emission Model for Line Sources (TREM) [2], using vehicles counting data. Emission and meteorology information is defined on an hourly or daily basis.

Regarding the type of most road traffic related air pollutants the model enables the simulation of passive or buoyant gas dispersion and deposition at local and urban scales. It was also designed to allow consideration of dispersion in rural or urban areas, including the treatment of building effects.

The output data includes the meteorological parameters and pollutant concentration at user-specified receptor points or spatially distributed over a regular grid. Different mean averaged concentration values can be defined, depending on the purposes.


Portability and computer requirements


URBAIR runs on a standard desktop PC under Windows.


CPU time

Model run-time varies from minutes to hours for cases studies depending on grid configuration used.



Daily PM10 simulation with URBAIR for Meri-Rastilla area in Helsinki .




[1]    Borrego, C., Martins, J.M., Lemos, S. and Guerreiro, C., 1997. Second generation Gaussian dispersion model: the POLARIS model. International Journal of Environment and Pollution 1997 - Vol. 8, No.3/4/5/6 pp. 789 – 795.


[2]    Borrego C., Tchepel O., Costa A., Amorim J. and A. Miranda (2003). Emission and dispersion modelling of Lisbon air quality at local scale. Atmospheric Environment , 37, 5197-5205.

última atualização a 15-04-2014
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