Global scale patterns and trends in tropospheric NO2 concentrations

Sammanfattning: Nitrogen dioxide (NO2) is an important air pollutant with both environmental and epidemiological effects. The main aim of this thesis is to explore spatial patterns and temporal trends of tropospheric NO2 concentrations globally using data from the OMI instrument aboard NASA’s Aura spacecraft. Additional aims are to validate the satellite data by comparing it to ground-based measurements, and to find the timing and magnitude of the most significant breakpoints over the study period of 2005 through 2018. The results show that there was statistically significant agreement between the satellite-based and ground-based datasets (r = 0.53). The global trend over the study period was negative (- 0.41 molecules cm-2 y-1), but a large difference was found between land and oceans (trends of - 1.84 molecules cm-2 y-1 and 0.35 molecules cm-2 y-1, respectively). USA, western Europe, India, China and Japan were identified as hotspot areas with high NO2 concentrations, while all these areas had negative trends over the study period. Finally, it was found that the year 2008 had the highest number of significant breakpoints, out of which almost all were negative