Multilinear regression analysis of the 65‐year Tromsø total ozone series

Abstract

The 65‐year total ozone record from Tromsø, Norway (69.7°N, 18.9°E), has been analyzed using multiple linear regression. Parameters included are modified linear depletion term, Northern Hemisphere teleconnection patterns, local temperature at the 30‐mbar level, stratospheric aerosols, Quasi‐Biennial Oscillation (QBO), and solar activity. Because of the availability of most input parameters, the analysis was limited to the period 1950–2001. All multiple correlation coefficients found are above 0.7, most even larger than 0.8. The series reveals a linear depletion term of about 9% decrease/decade in March/April since the late 1970s, decreasing to few percent in summer. The depletion term is insensitive to the envelope function (linear versus equivalent effective stratospheric chlorine), but highly sensitive to the modification term, forcing the contribution to zero in years with early vortex breakup. Aerosol‐induced depletion is found throughout late winter and spring, while the QBO is of importance in summer. Midstratospheric conditions, parameterized by the 30‐mbar level temperature, are dominant throughout the winter half year from September to February. Teleconnection patterns reveal a complex contribution, with no single pattern being persistently dominant over several months. The Polar‐Eurasian pattern is most prominent in midwinter, the North Atlantic Oscillation pattern in March. In May, the East Atlantic Jet pattern is dominant, while in June the Pacific Transition pattern is the most prominent parameter in the analysis. This variability of teleconnection pattern contributions is probably caused by the changing influence of air masses on the local tropopause altitude, with a dominant influence of North Atlantic and Arctic patterns in winter/spring, and of lower‐latitude patterns in summer and early autumn.