Research study shows the way for cleaner air

Many Swedish towns must find solutions in order to be able to meet the requirements the EU is making on clean air. The calculation model SIMAIR provides realistic information as to how particles and other substances are dispersed in the air. This is confirmed through a unique research study at SMHI.

Traffic environments in 20 Swedish cities have been studied. Hamngatan in Karlstad is one example.
Foto Stefan Andersson

For the first time, extensive scientific evaluation has been carried out for a Swedish air quality model. The analysis compares air quality measurements with model calculations for 20 Swedish towns. This is based on the EU´s requirements for clean air which regulates the concentration of particles in the air, particles which are mainly dispersed from traffic. Substances such as nitrogen oxide and benzene are also covered by the EU Air Quality Directive.
"It is primarily a problem of clean air around heavily trafficked roads lined by tall buildings. A number of Swedish towns need to find solutions to reduce these pollution levels," says Gunnar Omstedt, researcher at SMHI.

The model provides excellent results

The new research study confirms that the calculations carried out with SMHI's model SIMAIR provide excellent results when examining the emission and dispersion of pollutants in the air and can therefore be used to plan actions.

"The model calculations are consistent with our measurement data, we can even see a better outcome than the quality requirements the EU has formulated. We have also identified uncertainties and areas where the model requires further improvement, for example when calculating benzene," says Stefan Andersson, researcher at SMHI.

Improving air quality work

Traditionally, planners and those accountable at municipalities and air quality associations, for example, have only used measurements as a basis for action planning. Now that calculation models are able to supplement and to some extent replace some of the measurements, air quality work can be improved significantly. Instead of receiving information from individual measuring points, it will now be possible to study specific geographic areas. With the model, it is also possible to develop scenarios to see which measures produce the best effect.

A study is being carried out at the moment of streets with major air quality problems in Stockholm, Gothenburg, Malmö, Uppsala, Helsingborg, Karlstad and Norrköping. Calculations have been compared with measurements every hour over two years for most of the larger cities. Extensive work has been devoted to gathering data and checking its quality.

Inhalable particles

An analysis has been carried out commissioned by the Swedish Environment Protection Agency of the so-called PM10 particles, nitrogen oxide and benzene. PM10 particles are small inhalable particles with a diametre of less than 10 µm. The particles can cause and exacerbate heart, lung and vascular problems.

SMHI´s model system SIMAIR is a web service for the evaluation of the air quality in streets and their immediate surroundings. The amount of traffic and the type of traffic environment as well as meteorological factors such as wind, temperature, humidity and precipitation are important factors for the quality of the air and have been included in the model calculations.

Beräkningar och mätningar av luftkvalitet
Model calculations compared with measurements from the E6 at Gårda, Gothenburg, 2005.