Spectral UV Measurements at Sodankylä during 1990–2001

[1] A Brewer spectrophotometer MK II has measured UV irradiances since 1990 at Sodankyla (67°N,27°E), Finland. In this paper, the observed spectral features of the time series 1990–2001 are studied. In order to exclude the seasonal variation of irradiances due to the variation of solar zenith angle (SZA), only the narrow SZA interval from 63° to 65° was chosen. The data have been temperature, cosine, noise spike and wavelength-shift corrected. In order to study long-term changes in spectral UV irradiance, a linear regression line was fitted to the monthly mean irradiances from April to August. No statistically significant changes were observed for any months for the 12-year period 1990–2001. One reason is that the period is rather short in comparison to the high natural inter-annual variability of UV. The indistinct trend over this particular period could be also expected from the corresponding ozone changes: A decrease in the early 1990's with an increase toward more normal values in recent years, the smallest value occurring in the middle of the period. This makes the calculated UV changes highly dependent on the time period chosen. The biggest effect was seen in April, where the relative change at 305 nm varied from −5.0% to 12.1% per year for the periods 1993–2001 and 1990–1997, respectively. The analysis further shows that, although many other parameters, such as changes in cloudiness, aerosols, and albedo, contribute to UV changes, ozone has been a prominent factor at Sodankyla at the short wavelength end of the spectrum.

[1]  P. Ardanuy,et al.  Global relationships among the earth's radiation budget, cloudiness, volcanic aerosols, and surface temperature , 1992 .

[2]  Spike detection and correction in Brewer spectroradiometer ultraviolet spectra , 2003 .

[3]  R. Sausen,et al.  The impact of greenhouse gases and halogenated species on future solar UV radiation doses , 2000 .

[4]  Ultraviolet radiation in partly snow covered terrain: Observations and three‐dimensional simulations , 2001 .

[5]  M. Rummukainen,et al.  Prolonged stratospheric ozone loss in the 1995–96 Arctic winter , 1997, Nature.

[6]  H. Slaper,et al.  Variability of Ground-Level Ultraviolet: Model and Measurement , 2000 .

[7]  Christos Zerefos,et al.  Spectral measurements of solar UVB radiation and its relations to total ozone, SO2, and clouds , 1993 .

[8]  M. Caldwell,et al.  A STEEP LATITUDINAL GRADIENT OF SOLAR ULTRAVIOLET-B RADIATION IN THE ARCTIC-ALPINE LIFE ZONE' , 1980 .

[9]  G. C. Tiao,et al.  Analysis of long-term behavior of ultraviolet radiation measured by Robertson-Berger meters at 14 sites in the United States , 1997 .

[10]  Gunther Seckmeyer,et al.  Uncertainty of measurements of spectral solar UV irradiance , 1999 .

[11]  A. J. Miller,et al.  Factors affecting the detection of trends: Statistical considerations and applications to environmental data , 1998 .

[12]  J. Krzyścin,et al.  Aerosol impact on the surface UV radiation from the ground‐based measurements taken at Belsk, Poland, 1980–1996 , 1998 .

[13]  D. Wardle,et al.  The relationship between total ozone and spectral UV irradiance from Brewer observations and its use for derivation of total ozone from UV measurements , 1997 .

[14]  Joseph A. Wolkan,et al.  Introduction to probability and statistics , 1994 .

[15]  C. Booth,et al.  Solar irradiances over Ushuaia (/54.49° S, /68.19° W) and San Diego (/32.45° N, /117.11° W) geographical and seasonal variation , 2001 .

[16]  N. Y. Chubarova,et al.  Thirty year variability of UV irradiance in Moscow , 2000 .

[17]  Martin D. Müller,et al.  Variability of spectral solar ultraviolet irradiance in an Alpine environment , 2000 .

[18]  K. Leszczynski,et al.  INCREASED UV EXPOSURE IN FINLAND IN 1993 , 1995, Photochemistry and photobiology.

[19]  M. Chipperfield,et al.  Chemical depletion of Arctic ozone in winter 1999/2000 , 2002 .

[20]  A. Kylling,et al.  Transmittance of a cloud is wavelength‐dependent in the UV‐range: Physical interpretation , 1997 .

[21]  A. Dahlback,et al.  Analysis of the ozone soundings made during the first quarter of 1989 in the Arctic , 1992 .

[22]  Arve Kylling,et al.  The effect of clouds and surface albedo on UV irradiances at a high latitude site , 2000 .

[23]  Hideaki Nakane,et al.  Evolution of the Arctic stratospheric aerosol mixing ratio measured with balloon‐borne aerosol backscatter sondes for years 1988–2000 , 2001 .

[24]  A. Dahlback,et al.  Effects of stratospheric aerosols from the Mt. Pinatubo eruption on ozone measurements at Sodankylä, Finland in 1991/92 , 1994 .

[25]  A. Bais,et al.  Variability of UV‐B at four stations in Europe , 1997 .

[26]  Christos Zerefos,et al.  A note on the recent increase of Solar UV-B radiation over northern middle latitudes , 1995 .

[27]  J. Moan,et al.  Environmental UV Photobiology , 1993, Springer US.

[28]  Christos Zerefos,et al.  Quasi‐biennial and longer‐term changes in clear sky UV‐B solar irradiance , 1998 .

[29]  Peter Gies,et al.  Surface UV radiation over Australia, 1979-1992: Effects of ozone and cloud cover changes on variations of UV radiation , 1999 .

[30]  A. Bais,et al.  Record low total ozone during northern winters of 1992 and 1993 , 1993 .

[31]  A. Bais,et al.  Solar UVB measurements with the double‐ and single‐monochromator Brewer ozone spectrophotometers , 1996 .

[32]  J. Lenoble,et al.  Modeling of the influence of snow reflectance on ultraviolet irradiance for cloudless sky. , 1998, Applied optics.

[33]  James B. Kerr,et al.  Long‐term variations of UV‐B irradiance over Canada estimated from Brewer observations and derived from ozone and pyranometer measurements , 2001 .

[34]  Joachim Reuder,et al.  Aerosol effects on UV radiation in nonurban regions , 1999 .

[35]  A. J. Miller,et al.  Global and zonal total ozone variations estimated from ground‐based and satellite measurements: 1964–2000 , 2002 .

[36]  C. Zerefos.  Long-term ozone and UV variations at Thessaloniki, Greece , 2002 .

[37]  M. Degünther,et al.  Case study on the influence of inhomogeneous surface albedo on UV irradiance , 1998 .

[38]  Lars Olof Björn,et al.  Toward Solving the UV Puzzle , 2002, Science.

[39]  Arve Kylling,et al.  Effect of aerosols on solar UV irradiances during the Photochemical Activity and Solar Ultraviolet Radiation campaign , 1998 .

[40]  Hiroshi Kanzawa,et al.  Ozone depletion in and below the Arctic Vortex for 1997 , 1998 .