부산대학교 도서관

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 the Arctic. 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. Plain Language Summary: The ultraviolet radiation (UVR) from the Sun depends on the amount of ozone in the atmosphere. During March and April 2020, ozone concentrations in the Arctic atmosphere were exceptionally low and this led to large increases in UV radiation at the surface. These increases were quantified by analyzing data from ground‐based instruments at 10 Arctic and subarctic locations, as well as satellite data. UV levels were quantified with the UV Index (UVI), which measures the amount of "sunburning" UVR. The greatest UVI increases were observed between early March and mid‐April 2020. For several days, UVIs observed in 2020 exceeded measurements of previous years by up to 140%. 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%. However, these large relative anomalies occurred early in the year when the Sun is still low in the sky. UVI increases remained therefore small in absolute terms and did not exceed typical summertime UVI values under clear skies. Key Points: Record‐breaking low total ozone over the Arctic in March and April 2020 led to unprecedently large increases of UV radiation at Earth's surfaceRelative increases in the noontime UV Index exceeded 100% at several Arctic locations and surpassed historical means by more than six standard deviationsDespite large relative increases in UV radiation, absolute increases remained small because enhancements occurred at low solar elevations [ABSTRACT FROM AUTHOR]