The atmospheric dispersion models, which presently are part of the AirQUIS monitoring and surveillance system, have been presented for evaluation, discussions and model comparisons within the European Environmental Agency (EEA). 

At present these models are being further developed to match the user requirements, and to adequately meet the need for user friendliness. The models are already part of the models approved by Norwegian Authorities. They have also been used in several countries in Europe.

EPISODE (Grønskei, et al., 1993)
The EPISODE model is a mass-consistent, 3-layer (in the vertical) model solving the basic transport-diffusion equations. Based upon spatially distributed and time dependent input data of emissions, wind and turbulence, the model gives time-dependent concentrations in any receptor point within the modelling area.

Area-distributed sources (domestic, small industry, etc.) are treated within a grid system of typically 0.5-1 km. Superimposed on this, road traffic and point sources are treated in separate sub-grid models (Gaussian line-source dispersion of traffic emissions, and puff-trajectory model for point sources). Winter-type NO-NO2-O3 chemistry is included, and summer-type photochemistry calculation schemes are being introduced into the model.

The model runs on both UNIX and Windows platforms, and has been used for simulation of nitrogen oxides and ozone, and SPM (PM2.5) in Oslo (Larssen et al., 1994). The model has been included in an integrated air quality information system (AIRQUIS) at NILU. This includes an operative emissions model, and data (measured and calculated) presentation tools.

ROADAIR (Larssen and Torp, 1993; Torp et al., 1994)
The ROADAIR model has been developed as a combination of the Nordic Car Exhaust Model (developed in 1980-84 to enable the calculation of air pollution problems in street canyons), the EPA HIWAY model (for calculation of roadside air pollution) and a method for providing emission factors for different vehicles.

The principle was to estimate the maximum short-term concentrations of CO and NO2, taking account of the rush-hour traffic conditions, the canyon geometry and the worst-case dispersion conditions. From the first version 1.5 till the present version 3.1, the model has been developed to take into account non-canyon streets/roads, suspended particles, and the exposure of residents near the road network, based upon a building register. 

The version 3.1 is now used as a regulatory model in Norway, to determine in which areas/places abatement measures are necessary according to the law. The model calculates emissions and maximum short-term concentrations of CO, NO2 and PM at given distances from each junction in a defined road network, defined via a road and traffic data input register.

CONTILINK (Larssen et al., 1993).
The road network model CONTILINK, developed by the Norwegian Institute for Air Research (NILU), calculates emissions from a defined set of line sources. For each hour total concentrations of CO, NOx and PM10 are calculated at specific receptor points as a result of emission from the line sources based on hourly stationary meteorological conditions using Gaussian dispersion parameters. The modules used in the model are similar to ROADAIR.