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Research on the recovery of the ozone layer at the Finnish Meteorological Institute

Research on the recovery of the ozone layer at the Finnish Meteorological Institute

Time series of UV radiation and ozone column densities measured by FMI in northern Finland and Antarctic, together with albedo and aerosol measurements, form a unique data set providing information on the variation of the ozone layer thickness.

In addition to ozone and solar UV radiation measurements in Finland, the Finnish Meteorological Institute (FMI) performs such measurements in Marambio, Antarctica, as part of a long-term continuous cooperation on ozone sounding with the Servisio  Meteorológio Nacional Argentina (SMNA). The current UV radiation measurements continue the time series of the Spanish-Argentinean-Finnish Antarctic NILU-UV network.

Several factors affect solar UV radiation measured at the surface of the Earth; among the most important ones are the vertical column density of ozone, aerosol concentrations and surface albedo. "From the UV radiation measurements we can retrieve a lot of information about how climate change affects the ozone recovery, aerosol properties and surface albedo," tells FMI's scientist Kaisa Lakkala.

Solar UV radiation and total ozone measurements at Sodankylä, Finland. Picture: Kaisa Lakkala.

Extreme UV indices during spring time ozone loss episodes in the Antarctic

The measurements at the Antarctic NILU-UV network sites in Marambio and Ushuaia were analyzed in a recent study. FMI provided a traveling reference instrument to ensure the quality and homogeneity of the Antarctic measurements avoiding interruption due to removal of instruments for calibration elsewhere. It also made the measurements comparable with UV measurements performed in Finland and worldwide.

The research showed that at both Marambio and Ushuaia extreme UV indices were measured during spring-time ozone loss episodes. When the conditions were favorable, i.e., clear sky and the presence of the polar vortex at the station, the UV index could reach 11 even before midsummer. "This is a really high UV index especially at Marambio, which is located at the corresponding northern latitude at Kajaani in Finland – but in the Southern hemisphere. In Finland, the highest UV indices are measured around midsummer. They are between five and seven depending on the location in the North or in the South of Finland," says Lakkala.

Climate change affects the recovery of the ozone layer

The Montreal Protocol, an international treaty to regulate the production and use of chemicals that contribute to the depletion of Earth's ozone layer, was agreed in 1987. According to the latest WMO/UNEP Scientific Assessment of Ozone Depletion the stratospheric ozone layer has started to recover. However, the recovery will take decades and the uncertainties related to climate change may slow the process. Long-term UV and ozone measurements together with atmospheric model calculations are therefore needed to further study the effects of climate change.

The stratospheric ozone layer protects the Earth from the dangerous effects of exposure to solar UV radiation. Spring-time ozone depletion in the southern polar region was discovered in the 1980s from the analysis of satellite observations. Ozone depletion also occurs in the northern polar region, but not as pronounced as in the southern hemisphere.

Further information

Researcher Kaisa Lakkala, UV radiation,, tel. +358 40 747 6792

Researcher Outi Meinander, albedo,, tel. +358 50 569 8900

Researcher Laura Thölix, ozone,, tel. +358 50 380 2746

Professor Gerrit de Leeuw, aerosols,, tel. +358 50 919 5458

Lakkala, K., Redondas, A., Meinander, O., Thölix, L., Hamari, B., Almansa, A. F., Carreno, V., García, R. D., Torres, C., Deferrari, G., Ochoa, H., Bernhard, G., Sanchez, R., and de Leeuw, G.: UV measurements at Marambio and Ushuaia during 2000–2010, Atmos. Chem. Phys., 18, 16019-16031,, 2018.

WMO/UNEP Scientific Assessment of Ozone Depletion:

WMO/UNEP 2018; Scientific Assessment of Ozone Depletion: 2018, Executive Summary, World Meteorological Organization Global Ozone Research and Monitoring Project, Report No. 58. (pdf)

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