Trends in erythemal doses at the Polish Polar Station, Hornsund, Svalbard based on the homogenized measurements (1996–2016) and reconstructed data (1983–1995)

摘要

Erythemal daily doses measured at the Polish Polar Station, Hornsund(77°00′ N, 15°33′ E), for the periods 1996–2001 and2005–2016 are homogenized using yearly calibration constants derived fromthe comparison of observed doses for cloudless conditions with thecorresponding doses calculated by radiative transfer (RT) simulations.Modeled all-sky doses are calculated by the multiplication of cloudless RTdoses by the empirical cloud modification factor dependent on the dailysunshine duration. An all-sky model is built using daily erythemal dosesmeasured in the period 2005–2006–2007. The model is verified by comparisonswith the 1996–1997–1998 and 2009–2010–2011 measured data. The daily dosessince 1983 (beginning of the proxy data) are reconstructed using the all-skymodel with the historical data of the column ozone from satellitemeasurements (SBUV merged ozone data set), the snow depth (for ground albedoestimation), and the observed daily sunshine duration at the site. Trendanalyses of the monthly and yearly time series comprised of the reconstructedand observed doses do not reveal a statistically significant trend in theperiod 1983–2016. The trends based on the observed data only (1996–2001 and2005–2016) show declining tendency (about −1 % per year) in themonthly mean of daily erythemal doses in May and June, and in the yearly sumof daily erythemal doses. An analysis of sources of the yearly dosevariability since 1983 shows that cloud cover changes are a basic driver ofthe long-term UV changes at the site.