Recent Changes in Surface Ultraviolet Solar Radiation and Stratospheric Ozone at a High Arctic Site

Abstract

In 1888, photographic observations of the solar spectrum were made on top of Teide peak, Tenerife, Spain (Cornu 1890). Based on these measurements, the limit of the spectrum was set at 2922 A. Cornu concluded that the lack of measurable radiation below this limit was due to strong absorption in the atmosphere above. Hartley (1880) suggested that the atmosphere contained ozone. This was later confirmed by Fabry and Buisson in 1913. They performed accurate measurements and concluded that the amount of ozone corresponded to a 3-mm-thick layer of pure ozone at standard temperature and air pressure. This corresponds to 300 Dobson Units (DU), which is the commonly used unit for total ozone amount in the atmosphere, i.e., the amount of ozone in a vertical column from the earth’s surface to the “top” of the atmosphere. The pioneering work of G.M.B. Dobson (1889-1976) led to the construction of the famous Dobson spectrophotometer for accurate measurements of atmospheric ozone. Dobson instruments constitute the basis of the global network for measurements of atmospheric ozone and are still considered to be the most accurate instruments. After the discovery of the Antarctic ozone ‘hole’ in the mid-1980s there has been increased international interest in measurements of stratospheric ozone and surface UV radiation. Ozone depletion is not confined to high southern latitudes. Numerous ground-based and satellite measurements have confirmed a downward trend in the Northern Hemisphere as well. Unfortunately, the times series of high quality instruments for measurements of surface UV radiation at high northern latitudes are too short for trend estimates. The objective of this work is to describe the changes in surface solar UV radiation and total ozone during the last two decades at a high Arctic site, Ny-Ålesund, Spitzbergen, 79°N, by means of ozone data from satellites, ground-based ozone and UV instruments, and radiative transfer calculations.