Anyone who has spent more than one winter in Munich knows the phenomenon: In the city it is gray and cold for days, sometimes for weeks. But if you pull yourself up and climb the next local mountain, you will be rewarded with sun and warmth.
Why does Munich so often sink into fog every autumn and winter while the sun is shining in the mountains?
Gudrun Mühlbacher: That is due to the inversion weather conditions that we have quite often in Munich. Usually the air gets colder the higher you go. In the case of an inversion, this is exactly the opposite: the temperature increases with altitude. So-called soil inversion is typical for Munich. Due to the radiation of the ground at night, the layer of air immediately above it cools down more than layers above. But if the solar radiation is not so strong, these inversions will resolve more poorly.
Under what conditions does the mist soup form?
Especially when there is little wind, there is no mixing. It’s like being in a saucepan in which you don’t stir – the temperature differences can become quite large and the layers form. Such weak wind locations are often found with a strong high. And when the sun is low, as in winter, the fog no longer dissolves.
Do these weather conditions also have something to do with smog?
In extreme cases, yes. Especially in winter, when there is heating everywhere and more people switch from bicycles to cars, the pollutants can accumulate strongly because there is no air exchange.
The German Weather Service, which has its headquarters in Offenbach am Main, has its own branch in Munich. Gudrun Mühlbacher is the head of the Munich branch and the regional climate office.
(Photo: oh)
At what altitude are there chances of sunbeams and fresh air?
You are usually quite safe over 1500 meters. It is usually warmer in the mountains – everyone knows the pictures of skiers lying in the sun in the snow. The height from which you are above the clouds also depends on the type of inversion. In the Harz, for example, the clouds hang on the peaks. You are in the fog 300 days a year. The Alps are just higher and there are different air flow systems there.
And how can people in the city know that the sun is coming out up on the mountain?
Looking into a webcam actually helps quite well. Most of the time, inversions are also announced. For example, when the weather report says: “Today there is very little wind.” And then I look out and it’s foggy – then there’s usually a very good chance that it’s a little nicer in the mountains. But it can also be that the peaks are hanging in the clouds. Several weather systems can also overlap.