Even if a foggy Lake Constance corresponds to the cliché and has already served as a backdrop in many films: the reality is different. According to a report by the “Südkurier” today, the number of hours of fog per year is decreasing.
While in the 1980s, according to measurement data from the German Weather Service (DWD), 400 or even 600 hours of fog per year were normal, these values have hardly been reached since 2000. Since then there have been less than 200 hours of fog a year at the lake five times.
Otto Klemm, Professor of Climatology at the University of Münster, cited global warming and less air pollution as reasons. “Warm air can hold more water vapor than cold air,” he told the newspaper.
Relative humidity only increases when temperatures drop, until fog can form at around 100 percent humidity. High temperatures, on the other hand, mean less relative humidity and therefore less fog.
In order for fog to form, so-called condensation nuclei are also needed – i.e. particles in the air. When there are many condensation nuclei, many small fog droplets are formed, which scatter the light more, severely reducing visibility. “If there are fewer particles in the air because it’s cleaner, there’s less dense fog,” Klemm said. The fact that there is less fog is a global phenomenon. “With a few exceptions, the fog has been diminishing for decades.”
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