Multi-decadal Trend Analysis of Total Columnar Ozone Over Thessaloniki
With 33 years of continuous measurements, Thessaloniki has one of the world’s longest time series of the total ozone column (TOC) derived from a single monochromator Brewer spectrophotometer deployed since March 1982. We use the multi-decadal time series as a unique dataset for analysis of long-term changes in TOC and its parametric dependencies. We apply multiple linear regression (MLR) to monthly mean values of TOC and five proxies in the framework of a piece-wise linear trend (PWLT) model. We also perform a nonlinear time series decomposition using singular spectrum analysis (SSA) to obtain the monthly mean trend, periodicity and residual noise at mid-latitude. Both models confirm that the negative trend in TOC from 1982 exhibits a turning point during 1997 and strongly anti-correlates (ρ = −0.69 for MLR and ρ = −0.95 for SSA) with the amount of the ozone-depleting substances as represented by the EESC. Post-1997 ozone recovery is found to be evident but not statistically-significant, for the majority of the months, in the linear model. The reconstruction of TOC from the noise-free nonlinear trend model extracted from SSA is an improvement over the standard MLR linear PWLT model (ρ = 0.89 as compared to ρ = 0.76).
KeywordsMultiple Linear Regression Multiple Linear Regression Model Singular Spectral Analysis Trend Component Total Ozone Column
We would like to thank Dr. Irina Petropavlovskikh for her constructive comments in the original manuscript.
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