Abstract
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.
Highlights
Total ozone columns (TOC) over the northern polar cap were exceptionally low in late winter and early spring (February–April) of 2020 (Lawrence et al, 2020)
We assembled maps of monthly TOC and UV Index (UVI) anomalies from OMI data for latitudes north of 45°N and compared UVI anomalies extracted from these maps with anomalies calculated from the ground‐based measurements
For European sites, the largest TOC anomalies occurred in early April with deviations ranging between −30 and −40%
Summary
Total ozone columns (TOC) over the northern polar cap (latitudes > 63°N) were exceptionally low in late winter and early spring (February–April) of 2020 (Lawrence et al, 2020). The low TOCs in 2020 were partially caused by an exceptionally strong, cold, and persistent stratospheric polar vortex, which provided ideal conditions for chemical ozone destruction to occur (Grooß & Müller, 2020; Manney et al, 2020; Wohltmann et al, 2020). Temperatures low enough to promote polar stratospheric cloud formation within the vortex developed early in the season and enclosed about one third of the vortex volume on average. These conditions are unprecedented since at least 1979/1980; 2019/2020 had the greatest Arctic ozone loss potential on record. The conditions leading to anomalously low TOCs are discussed further in other papers of this special collection (Grooß & Müller, 2020; Lawrence et al, 2020; Manney et al, 2020; Wohltmann et al, 2020)
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