Ozone layer above Switzerland
Ozone is a gas that has the property of absorbing a portion of the ultraviolet radiation emanating from the sun. It is present throughout the stratosphere at an altitude of between 10 and 40 km, where it forms the so-called ozone layer. The destruction of ozone molecules is not caused directly by the substances that deplete the ozone layer, but rather by their degradation products (chlorine, bromine), which are formed under the particularly intense UV radiation in the stratosphere. This indicator reflects the evolution of the ozone layer and is an indication of the efficiency of measures taken to preserve it and of the necessity of further intervention.
Since the minimum level recorded in 1993 due to the temporary increase in the concentration of chlorine in the stratosphere following the eruption of Pinatubo, the average concentration of ozone over Arosa first tended to rise slightly each year. For the last ten years it has remained more or less stable. Due to the longevity of ozone depleting substances in the atmosphere, and their continued emission from existing stocks, in particular insulation foams and refrigeration systems, a return to the initial level is not expected before 2060, and will also depend on other related factors, such as climate change. In order to reach its 1980 level, the ozone concentration must rise by 5%. This corresponds to a linear increase of 0.075% per year between ca.1995 and 2060. Between 1995 and 2010, the increase should therefore have amounted to 1.15%. Since the ozone concentration remained more or less stable during this period, the target can deemed to have been missed by these 1.15%. As this value is lower than 2%, the state of the ozone layer above Switzerland can nevertheless not be assessed as completely negative.
This indicator illustrates the global state of an environmental parameter at a given spot on our Planet. A comparison with data from other countries does not make sense, since dissimilarities between regions are more likely to be due to local variations in the Earth climatic system than to differences in the effects of ozone-depleting substances.
The transparency of the atmosphere to solar UV radiation is measured using Dobson and Brewer spectrometers. These measurements are used to calculate the amount of ozone present in the air column above the Arosa observatory.