Total ozone content in southeastern South America: A statistical analysis of 45 years of satellite data.

Abstract

This study investigates the Total Ozone Content (TOC) over Southeastern South America (SESA) using more than 45 years of satellite-derived data and ground-based Dobson spectrophotometer measurements over three sites. Satellite datasets from several missions were validated against ground-based Dobson observations, showing strong agreement with correlation coefficients exceeding 0.94 and biases below 2%. MERRA-2 monthly reanalysis data, also validated in this study, was used to complement satellite datasets for gapfilling. The analysis identified three distinct periods in ozone trends: a depletion phase (1979–1993) consistent with pre-Montreal Protocol conditions, a recovery phase (1994–2003) marked by positive trends, and a stabilization phase (2004–2023) with weak, less significant positive trends. Seasonal cycles during the stabilization period were obtained, showing lower ozone levels from January to May (around 265 DU), peaking in August to October (305 DU), with a consistent latitudinal gradient characterized by lower values at northern sites. A simple and accurate parametrization of the annual cycle was also derived at daily level, enabling daily ozone estimates and as a reference for anomaly detection. These findings contribute to a deeper understanding of ozone variability in the region, supporting global monitoring efforts and offering a foundation for evaluating the impacts of ozone dynamics on regional climate.