Hot spell pushes 'zero-degree' line to record height in Switzerland
by AFP Staff Writers
Geneva (AFP) Aug 21, 2023

A hot spell enveloping Europe has pushed the zero-degree line -- the altitude at which the temperature dips into the minus -- to a record height of nearly 5,300 metres (17,400 feet) in Switzerland.

The zero-degree line is determined by meteorologists using weather balloons that take off twice a day from Payerne in western Switzerland.

MeteoSwiss said the new height was clocked overnight from Sunday to Monday at 5,298 metres, "which constitutes a record since monitoring began in 1954".

The previous record of 5,184 metres was set on July 25 last year.

"The area known as the zero-degree isotherm is the threshold between air layers with temperatures above 0C at lower altitudes and those with temperatures below freezing at higher altitudes," MeteoSwiss said.

"Among other things, the zero-degree isotherm affects vegetation, the snow line and the water cycle, and so has a considerable impact on the habitats of humans, animals and plants alike," it added, calling the marker "an integral part of weather forecasts in the Alpine region".

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