What does winter on the industrial Highveld look like?

Posted on July 09, 2021

These images are typical Mpumalanga Highveld images from mid-winter. Typical, because the effect of the general atmospheric circulation patterns of the region can be seen on these. Circulation patterns of the South African Highveld during winter are strongly anti-cyclonic, associated with divergence and subsidence. This means that air masses tend to not rise, but rather settle near the ground.

This circulation can cause increased stability over the region; these stable atmospheric conditions prevent the dilution and dispersion of air pollution, especially when emitted from sources near the surface (such as, emissions from domestic fuel burning, car exhausts, or industries). In other words, pollution is also often trapped near the surface by the anti-cyclonic (subsiding air) conditions. The benefit of this is that South African Highveld winters are normally characterised by beautifully clear skies.

On the images we can see smoke and haze close to the ground; probably, in part, from settlements surrounding the area, burning charcoal.  Some of our most typical challenges in terms of indoor and outdoor pollution are particularly severe in these types of areas. We can also see the plume from the smokestack almost going sideways and, crucially, above the haze (trapped pollution) you see on each image.  Smokestacks (chimneys) are normally built high and stand tall above the surface. Their aim is to emit harmful pollutants above the very stable layers that form near the Earth’s surface, so that these emissions can be more efficiently diluted and dispersed.

Text: Anzel de Lange & Emma Archer

Photos:  Jacob van Garderen

- Author Department of Geography, Geoinformatics and Meteorology
Published by Christel Hansen

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