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Tirol explained: Föhn
A famous downdraft wind gives many Tyroleans a headache. The foehn, which usually blows over Innsbruck from the south, is a complex phenomenon that actually affects the body. We spoke to two experts about it.
It can be found in the Rocky Mountains, in South America, in Japan, in Antarctica and in the Alps, generally everywhere where there are mountains. We are talking about the downslope wind, known in this country as the foehn. The warm, strong, mostly dry wind sometimes blows for days in and around Innsbruck. Its gusts reach hurricane force with wind speeds of up to 150 km/h (the record is over 200 km/h). Some residents of the Föhn areas complain of headaches and other ailments at times, and certainly of dishevelled hair - even air traffic has to be adjusted accordingly.
Alexander Gohm and Christian Schubert deal with the Föhn from different scientific perspectives: one is a meteorologist at the Institute for Atmospheric and Cryospheric Sciences at the University of Innsbruck, the other is a psychologist and doctor at the Innsbruck Clinic.
Alexander Gohm has specialised in alpine wind phenomena in his research. "Wind is the result of a current that tries to equalise a pressure difference," he explains. To begin to understand the Föhn, you have to start with the basics. Large-scale and often humid currents hit the Alps from the Mediterranean. In the so-called "high-reaching southern foehn", the main Alpine ridge blocks this current on the windward side (in this case the southern side) - the air is forced to descend into the northern valleys (for example into the Inn Valley). This causes the air masses to warm up. Gohm explains this effect with a bicycle pump: "When I squeeze a bicycle pump, I notice that it gets warm over time." As it sinks into the valley, the air is compressed due to the rising air pressure and heated adiabatically (i.e. without heat exchange). For this reason, the temperature of the wind rises by around one degree Celsius per hundred metres of altitude.
This process is just one of many that explain the warming caused by Föhn winds and thus the temperature difference between the north and south sides of the Alps. Precipitation can be another favourable factor: In some cases, the large-scale flow that hits the Alps from the south is very humid. When it is finally forced to rise on the windward side, the water vapour condenses, leading to cloud formation and precipitation. The heat released in the process causes higher temperatures in the valleys on the northern side of the Alps as it sinks downwind. However, the Föhn only warms up in this way if there is sufficient precipitation.
It is difficult to say when the Föhn will finally be felt in Innsbruck. The cigar clouds or foehn fishtails that indicate foehn conditions can already be seen in the sky, even though there is no wind in the valley. The reason for this is a lake of cold air in the Inn Valley. Alexander Gohm tries to simplify the phenomenon: "The cold air lake is like a bathtub filled with water." The Föhn wind flows from the Brenner Pass through the Wipptal valley, a natural gap in the mountains (technically known as the "Föhnschneise"), sideways into the Inntal valley and fills the lake. The mixing of the warm foehn air and the cold air lake causes headaches, especially for pilots. Turbulence rages over the city and the wind direction can change suddenly.
During foehn periods, airport staff often have to inform approaching aircraft at short notice which side they can land from. So-called fractus, i.e. shredded clouds or "rotor clouds", indicate this precarious situation. In the Innsbruck area, rotor clouds often form in front of the Nordkette mountain range. There is a strong upwind zone, a "hydraulic jump", which can be compared to an obstacle in a river over which the water flowing downstream jumps. It can be "like a washing machine" in a rotor cloud.
The foehn fishtails (cumulus lenticularis) hovering above the ridge level are created by wave movements in the atmosphere. At the crest of the wave, the air expands, cools and condenses - forming clouds. The flow over the Alps ultimately gives them their shape.
With the PIANO research project, Alexander Gohm is attempting to investigate the Föhn on a large scale. It is important for everyday life in the Inn Valley to find out more about this natural phenomenon. "The aim of the project is to better understand the processes that contribute to the breakthrough and collapse of the Föhn."
For Christian Schubert, the hairdryer is also a complex dynamic system. Using a specially developed research design, the "integrative individual case study", he investigates the influence of complex phenomena on humans, in short: Schubert wants to find out, among other things, how the foehn affects the immune system and the development of diseases. The foehn is a combination of differences in wind speed, temperature, air pressure and humidity. "We know that these four weather elements have an effect on the body and psyche," explains Schubert. To date, other Tyrolean scientists have discovered that the properties of the foehn can increase the suicide rate in depressed people and the rate of heart attacks, for example. The general health of sensitive people is also likely to be affected by the foehn wind.
It's not just the intensity of the weather that can be stressful for the mind and body, but also, for example, the high-frequency fluctuations in air pressure that occur during foehn periods. Christian Schubert knows: "The body has to resonate in these situations. When weather phenomena change significantly, we also change and have to adapt resonantly to these conditions." One of the mysteries of research is the question of exactly how these weather phenomena affect people - it is not yet clear whether the weather changes the psyche via the immune system or the immune system via the psyche and what interactions exist in this regard.
Schubert takes weather-sensitive people who complain of headaches and other complaints during foehn periods seriously. Well-founded research into the connection between foehn winds and health is still relatively new. Nevertheless, Schubert is convinced that tangible results could positively change the way we deal with widespread weather sensitivity. Until then, the only consolation is that you are not the only one with a headache on foehn days.
