Meteorological data
Any study of air pollution should include a study of the weather patterns (meteorology) of the local area because the fate of air pollutants is influenced by the movements and characteristics of the air mass into which they are emitted.
If the air is calm and pollutants cannot disperse then the concentration of these pollutants will build up. Conversely, if a strong, turbulent wind is blowing any pollution generated will be rapidly dispersed into the atmosphere and will result in lower concentrations near the pollution source.
The measurements of wind speed and direction, temperature, humidity, rainfall and solar radiation are important parameters used in the study of air quality monitoring results and to further understand the chemical reactions that occur in the atmosphere. Meteorological monitoring is used to predict air pollution events such as inversions, high pollutant concentration days and to simulate and predict air quality using computer models.
Wind speed and direction
Wind speed and direction measurements are important for air quality monitoring. If high pollutant concentrations are measured at a monitoring station the wind data recorded at the station can be used to determine the general direction and area of the emissions. When the likely source or sources have been identified they can then be managed to reduce the impacts on air quality.
Wind speed is measured using an instrument called an anemometer. In this picture a "cup wheel" anemometer is turned by the wind which in turn generates an electrical current that is a measure of the speed of the wind.
To complement measurements of wind speed, wind vanes are used to monitor wind direction.
This picture shows how the wind vane is blown by the direction of the wind. These movements are recorded to calculate the wind direction.
The department also uses sonic anemometers at some stations. Sonic anemometers operate on the principal that the speed of wind affects the time it takes for sound to travel from one point to another. If the sound is travelling in the direction of the wind then the transit time is decreased.
Conversely, if it is travelling in the opposite direction to the wind the transit time is increased. Sonic anemometers emit sound waves, record the time taken to receive the wave at the other end of the instrument, then convert the value into the wind speed. By monitoring the speed of sound along two different axes, wind direction is also able to be measured.
The measurement of meteorological parameters is important to gain an understanding of the impacts of a region's meteorology on air pollutant concentrations, the prediction of inversions, and for the study of windfield and dispersion modelling.
An example of the impacts of calm and windy conditions on carbon monoxide levels adjacent to a major road in Brisbane over a one-year period is shown in the graph below. 
The carbon monoxide emitted from road traffic is well dispersed during summer by strong winds, resulting in lower concentrations. However, during winter carbon monoxide concentrations peak as the air is calmer and does not disperse the pollutant as quickly, resulting in higher concentrations.
Last updated: 07 April 2006