Atmospheric dispersion modelling provides a mathematical description of the behaviour of pollutants in the air for a specific period of time. This is an essential tool used by government agencies, industry and consultants for air quality assessment, especially when decisions regarding approvals and permits have to be made.
The dispersion models are very often the only economically viable methods which can be used to understand the interaction of existing or future pollution emission sources with meteorology, topography and air quality at specific locations and times.
Some of the dispersion models are more complex than others and all models require inputs (emissions, meteorology and topography). If these inputs are of poor quality, then the model output will also be of poor quality.
It is the responsibility of professionals conducting modelling to make sure that the appropriate model is selected for a given situation, that all the inputs have been checked for completeness and accuracy, and that testing has been done to ensure that the model has been used correctly.
Air dispersion models have their limitations. One cannot expect one model to be suitable for use in all geophysical, atmospheric and source situations. After all, air quality modelling relies on the physics and chemistry of dispersion and reactivity of pollutants in the atmosphere and mathematical formulations of the physics and chemistry being translated into computer programs carrying out the corresponding calculations. Interpreting the output of modelling and assessing how much confidence should be placed in the results involves considerable expertise and experience which are critically important to achieving useful results.
Modelling is an integral part of air quality management in Tasmania. The EPA Division has specialist dispersion modellers engaged in a number of practical modelling exercises.
Consultants should contact the EPA Division modelling specialist for advice on numerical models accepted for atmospheric dispersion modelling in Tasmania and to obtain a copy of draft guidelines.