Record-Breaking Increases in Arctic Solar Ultraviolet Radiation Caused
by Exceptionally Large Ozone Depletion in 2020
Measurements of solar ultraviolet radiation (UVR) performed between
January and June 2020 at 10 Arctic and subarctic locations are compared
with historical observations. Differences between 2020 and prior years
are also assessed with total ozone column and UVR data from satellites.
Erythemal (sunburning) UVR is quantified with the UV Index (UVI) derived
from these measurements. UVI data show unprecedently large anomalies,
occurring mostly between early March and mid-April 2020. For several
days, UVIs observed in 2020 exceeded measurements of previous years by
up to 140%. Historical means were surpassed by more than six standard
deviations at several locations. In northern Canada, the average UVI for
March was about 75% larger than usual. UVIs in April 2020 were elevated
on average by about 25% at all sites. However, absolute anomalies
remained below 3.0 UVI units because the enhancements occurred during
times when the solar elevation was still low.