Defense
Student: Arthur Dias Freitas
Program: Meteorology
Title: "Satellite Observations of Trace Gases Vertical Columns: Exploring Temporal and Spatial Complexities"
Advisor: Profa. Dra. Adalgiza Fornaro
Judging Committee:
- Profa. Dra. Adalgiza Fornaro - Presidente e Orientadora - IAG/USP
- Profa. Dra. Samara Carbone - UFU (por videoconferência)
- Profa. Dra. Débora Souza Alvim - EEL/USP (por videoconferência)
- Prof. Dr. Gregori de Arruda Moreira - IFSP (por videoconferência)
- Profa. Dra. Flávia Noronha Dutra Ribeiro - EACH/USP (por videoconferência)
Other Members:
- Profa. Dra. Rita Yuri Ynoue - IAG/USP
- Profa. Dra. Márcia Akemi Yamasoe - IAG/USP
- Prof. Dr. Nilton Évora do Rosário - UNIFESP
- Prof. Dr. Thiago Nogueira - FSP/USP
- Prof. Dr. Leonardo Hoinaski - UFSC
Abstract:
Satellite observations have become an essential tool for the global monitoring of atmospheric chemical compounds, enabling continuous data acquisition with high spatial coverage. Although these instruments primarily measure vertically integrated atmospheric columns, studies indicate that these measurements can reflect near-surface variability when combined with meteorological and reanalysis data. In this context, the hypothesis of this study is that the spatial and temporal variability of trace gases observed by satellite is consistently associated with emission sources, geographic characteristics, and meteorological conditions, which can be evaluated through comparisons between regions with distinct atmospheric dynamics. In this work, vertical column densities (VCDs) of formaldehyde (HCHO), nitrogen dioxide (NO2), sulfur dioxide (SO2), ozone (O3), and carbon monoxide (CO), retrieved from the TROPOMI instrument, were analyzed over the São Paulo State (Brazil) and France for the 2019–2023 period. Surface meteorological data (CETESB and Airparif) and vertical profiles from MERRA-2 were used to interpret the variability of the compounds and support the estimation of near-surface concentrations and tropospheric ozone. Additionally, the HCHO/NO2 ratio (FNR) was calculated to identify ozone formation regimes, distinguishing between VOC-limited, NOx-limited and transitional conditions. The results reveal spatial gradients and seasonal variability in both regions. In the São Paulo State, higher levels of HCHO (~14.0 x 1015 molecules cm-2) and NO2 (~9.0 x 1015 molecules cm-2) are concentrated in the Metropolitan Area of São Paulo (MASP), associated with vehicular and industrial emissions, with secondary maxima along biomass burning corridors during the dry season; SO2 ranges from 19.2 to 35.9 x 1015 molecules cm-2. In France, HCHO (~8.0 x 1015 molecules cm-2) and NO2 (~6.0 x 1015 molecules cm-2) show a more uniform distribution, with higher concentrations in urban areas, while SO2 reaches higher levels (~60.0 x 1015 molecules cm-2), influenced by industrial sources and winter conditions. In both regions, CO shows a more homogeneous distribution, with seasonal maxima in winter. The FNR analysis indicates a VOC-limited regime in the urban core of São Paulo, transitioning to NOx-limited conditions in peripheral areas, whereas Paris exhibits a predominantly transitional regime, with a tendency toward NOx limitation. Through the integration of multi-year satellite observations, meteorological parameters and reanalysis data, this study advances the understanding of how urbanization, climate and emission patterns shape atmospheric chemistry in megacities of different hemispheres. The results highlight the relevance of TROPOMI data for diagnosing regional pollution regimes, demonstrate the utility of the FNR as a tool for ozone management strategies, and underscore the complex interplay between emissions, meteorology and urban morphology in governing atmospheric reactivity. Collectively, the findings contribute to a deeper understanding of how anthropogenic and environmental drivers jointly influence air quality dynamics in urbanized regions.
Keywords: formaldehyde, megacity, ozone, TROPOMI, troposphere