Dr. Schmidt explains the world: Where does the storm in the subway shaft come from?

I regularly take the subway in Berlin. Can you explain to me where the storm at the subway exit is coming from?

I haven’t experienced a storm there yet. A little windier. The core is the fact that the subway runs in a relatively closed tube and it is not empty. This means that the train pushes the air in front of it. And then it flows into the subway station.

But I’m talking about gusts of wind that are not noticeable on the platform, but only on an intermediate level towards the exit. So that the hair flutters really hard.

Well, the hair. It doesn’t take that much for that.

Believe me, these are squalls that you really have to brace yourself against. And these are not available at other subway stations.

Where is it?

Eisenacher Straße subway station.

So I have to take a look at this subway station. I haven’t seen it in sharpness yet. Of course, it may be that there is additional wind above ground. If it blows in a suitable direction, there is additional suction from above. That depends on which direction the subway entrances give free access to the wind. If there is a nice open stretch above ground in the northwest-southeast axis, which is where most of our stronger winds occur, it could be that this could lead to strengthening. But that would be speculative.

Could it also be the other way around? That something is blocking the way at the top and the wind is therefore moving downwards?

That would be an equally good option. When wind is redirected from buildings into the subway, you have a similar wind tunnel effect to some new housing developments. Where ten-story trees stand parallel in a suitable direction, the wind between them is stronger than anywhere on an open area.

Wind always comes from different directions.

In principle this is true, but there is a prevailing direction. For us it’s from the northwest.

What does it mean to us? Berlin?

Here in Central Europe. I’m one of those people who was taught at pioneer hiking days – in the West it would probably have been the Boy Scouts -: If you want to orientate yourself in the forest, then the side of the trees that is a little more overgrown with moss and lichen is the one Rule Northwest.*

Why does the wind come more from the northwest?

This is the typical wind system in the northern hemisphere in the temperate zone. From the North Sea and Atlantic direction. In the layer closer to the ground, certain directions dominate. This has to do with the rotation of the Earth and the larger wind system in which we are integrated. Of course there are always deviations. When low and high pressure areas are distributed very differently, there is also a southerly wind, which the Bavarians in the Alps know as a foen.

Wind is also extremely important for air quality in the city.

You should definitely build in such a way that the cooling winds that occur in summer can pass through easily. But it’s not just street corridors that are important, but rather larger green spaces. Berlin is doing great compared to Paris, but considering what the climate will demand of us in the foreseeable future, there is still a lot of room for improvement in Berlin.

Back to the subway shaft. Can’t you use this wind for something?

The effort would probably be too great. Using the waste heat from the subway would probably be much more attractive than the little bit of wind. I’ve had a similar question at another point: It’s quite warm in the subway tunnel. You should actually be able to use this heat. But this has so far been too complicated for most people involved. There is probably a place in Berlin where heat from the subway shaft is used to supply heat to a BVG depot. A church in Wedding that had a similar project encountered resistance because they would have had to lay pipes there. And the local civil engineering department was of the opinion that capacity should be kept free for other charitable purposes, not just for one church.

So people still have cold feet in church?

This is to be expected, especially in the age of rising gas prices. But whatever: Using the waste heat from the subway would probably be much more attractive than the little bit of wind.

* A reader corrected this view, which is still widespread even among sailors today: The meteorological data clearly say, at least for Berlin, that westerly winds predominate, even southwest winds are more common here than northwest winds.