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Issues

Variability and Change
    Ambient Air Quality
      Indoor Air Quality

        At a glance

        Fog in the Tamar Valley and Midlands

        The issue

        There are many meteorological conditions that can exacerbate air quality problems.

        The lack of cloud at night, which is common when a high-pressure system passes over the State, results in a net loss of radiation (heat) from the ground, causing the ground to cool dramatically. The cold surface cools the air above it, so the coldest temperatures are closest to the ground. Cold air is denser than warm air, so just like water, it flows downhill (i.e. cold air drainage) and pools in topographic low spots (frost hollows). These conditions are referred to as temperature inversions and are the most common meteorological conditions that can exacerbate air quality problems by trapping pollution near the ground.

        Temperature inversions are particularly evident during still winter conditions. Launceston and the northern and western suburbs of Hobart often experience inversions during the winter months, but they regularly occur throughout Tasmania. The amount of fog typically indicates the severity of the inversion.

        It is important to know what factors increase the potential for poor air quality so that modifications to behaviour/management can be made.

        This 'At a glance' section provides an overview of meteorological conditions. More detailed information is available in the Meteorological Conditions Issue Report. While no specific recommendation is presented on meteorological conditions, the issue is closely associated with recommendations on Total Exposure to Air Pollution and Ambient Air Quality Monitoring.

        Favourable news

        • While there is little that can be done about the meteorological conditions that can lead to poor air quality incidences, there is a considerable amount that can be done about the release of pollutants during such times. Significant work is being undertaken to reduce emissions, particularly wood heater smoke, in the worst areas (especially Launceston), and the benefits are becoming clear.
           

        Unfavourable news

        • Pollutants released into cold air drainage resulting from a temperature inversion are often trapped below the inversion layer, accumulating to high concentrations.
           
        • The most common pollutant that is concentrated in Tasmanian urban areas is particulates from wood heater smoke.
           

        Cold air drainage in a valley

        Uncertain news

        • There is limited monitoring and modelling of meteorological conditions that exacerbate pollution problems in Tasmania. This has hindered the ability to report against the indicator 'meteorological conditions that exacerbate air quality problems' as recommended in the National Atmosphere Key Indicator 3.11 (Manton and Jasper 1998).
           
        • The Bureau of Meteorology does currently provide an analysis of meteorological conditions that exacerbate pollution for Launceston during winter, but while the model used is a good basis for modelling other areas, further work is required before it can be properly instituted.
           
        • In the future, it is expected that more sophisticated estimates of meteorological conditions that exacerbate pollution could be analysed directly each day from the data assimilation process of the routine numerical weather prediction system of the Bureau of Meteorology.
           

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        Last Modified: 14 Dec 2006
        URL: http://soer.justice.tas.gov.au/2003/atm/1/issue/6/ataglance.php
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