Long-term trends of total ozone column over the Iberian Peninsula for the period 1979–2008

The objective of this work is to analyze the total ozone column (TOC) trends over the Iberian Peninsula during the last 30 years (1979–2008). This study is carried out using TOC data derived from the Multi Sensor Reanalysis (MSR), Total Ozone Mapping Spectrometer (TOMS) and Global Ozone Monitoring Experiment (GOME). The analysis of the long-term ozone trends is focused on two sub-periods (1979–1994 and 1995–2008) in order to detect changes in the ozone trend pattern. The results show that the ozone depletion was statistically significant at the 95% confidence level during the first sub-period (1979–1994) in the entire region of study (except in the Southerner locations), with linear trends from −4.5%/decade to −2.5%/decade. These linear trends present a clear dependence on latitude, being higher for the Northerner locations than for the Southerner. By contrast, the analysis of the second sub-period of study (1995–2008) shows positive ozone trends over the Iberian Peninsula, with the highest values (+2.5%/decade) in the Northeast of this region. This result indicates that the ozone layer may be responding as expected to the controls on ozone-depleting substances imposed by the Montreal Protocol. Additionally, a seasonal trend analysis is performed using the average of the deseasonalized monthly values for each season of the year. The seasonal analysis showed that the negative ozone trends during the first sub-period of study were statistically significant in the spring and winter, while that the seasonal ozone trends obtained during the second sub-period are positive but in general not significant at 95%.