Statistical analysis of total ozone measurements in Oslo, Norway, 1978–1998

Abstract

The total ozone series from Dobson spectrophotometer 56 (D56) operating at the University of Oslo (59.9°N, 10.7°E), Norway, from March 1978 to May 1998 has recently been reevaluated. Ozone trends for the time series are calculated using multiple regression models with explanatory variables for the 11 year solar cycle (lagged 22 months), the 2.5 year Quasi‐Biennial Oscillation (QBO) cycle, stratospheric aerosol loading from volcanoes, detrended temperatures at 100 hPa and 500 hPa levels, El Niño–Southern Oscillation (ENSO) events, and various teleconnection patterns. Six of the teleconnection explanatory variables examined are significant to a 95% confidence level in describing the observed total ozone variations. The year‐round total ozone trend in Oslo (±SD) is estimated to −4.2 ± 0.4 % per decade, whereas the winter and summer trends amount to −6.2 ± 0.9 % per decade and −2.4 ± 0.5 % per decade, respectively. The analyses imply that climatic and dynamical changes account for up to a 20% increase in winter ozone trend and a 40% decrease in summer ozone trend. The East Atlantic Jet is the single most dominating teleconnection pattern in Oslo and contributes to about 0.7 percentage points per decade change in summer total ozone trend. The regression analyses demonstrate that the start and termination dates of the ozone record are highly important for the trend results: The summer and winter ozone trend can change by 0.9 percentage points per decade if 1 year is included or omitted from the analyses.