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Flow and wave effects – phenomena at fog margins

While a sea of fog may appear static, it is actually in constant flux, as time-lapse photography shows. That is why the top of a band of fog hardly ever stays at the same altitude over the course of a day.

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There are various reasons for these movements:

  • When the air warms up during the day, the fog-top height tends to rise somewhat and then sink again at night. This effect is more pronounced in the autumn months than in winter.
  • At the transition zones of the fog, temperature and thus pressure differences arise towards the fog-free regions. This is why the fog is often drawn into the initially fog-free Alpine foothills during the day.
  • Just as in the ocean, a sea of fog is subject to waves passing through it.
  • Changes in pressure distribution, changing wind conditions at the fog top and large-scale uplift effects all strongly influence the movements of the sea of fog.

The images and time-lapse videos below illustrate some of these processes.

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