Ozone (O3) directly and indirectly affects human health (depending on the altitude it is sometimes referred to as “good” or “bad” ozone) and has an important role in the temperature structure of the atmosphere. Because of the impact of ozone on air quality and climate change, the objective of this thesis is to improve our understanding of the global distribution of atmospheric ozone in space and time, not just in the stratosphere, but also in the troposphere, where it directly affects living organisms.
In this thesis, ozone is measured with satellite-based instruments that measure reflected solar light in the Ultra Violet - VISible (UV-VIS) wavelength range (280 < λ< 330 nm). In the UV-VIS, the absorption crosss-ection of ozone varies by several orders of magnitude, providing the altitude information for the ozone distribution. The ozone profiles are retrieved from the measured radiation with the optimal estimation technique. To make optimal use of the advantages of both observations and atmospheric models, they are combined using the Kalman filter data assimilation technique.The assimilation output consists of regular gridded 3D ozone fields without missing data at regular time intervals.@en

Horizontal drilling and hydraulic fracturing have increased unconventional oil and gas extraction from shale reserves in the U.S. in the last decade, making up more than half of total U.S. oil and gas production at present. This activity results in NOx emissions in the extraction regions that are measurable from space using the Ozone Monitoring Instrument (OMI) on the NASA Aura satellite. The NOx emissions are a result of two different activities: (1) the drilling and hydraulic fracturing of new wells, and (2) the extraction of oil and gas after the well is completed. To separate the NOx emissions from drilling and extraction, a multiple linear regression to the NO2 columns as a function of time is calculated for 9 extraction regions using the number of drilling rigs and the oil and gas extraction data from 2007 until 2018. In 3 regions (Permian, Bakken, Eagle Ford) a significant correlation between measured and modeled NO2 columns is found, of which the Permian region shows the highest correlation. The analysis shows that half of the total NOx emissions in the Permian region can be attributed to emissions from oil and gas activities, and that both the drilling and extraction activities have an equal share in the emissions. A fuel-based oil and gas emission inventory shows a different split for NOx emissions from drilling and extraction in the Permian region, indicating drilling as the larger source. In other extraction regions, NO2 columns show poor correlation with the oil and gas activities due to the proximity of urban areas (Barnett, Denver-Julesburg, Haynesville regions), power plants (San Juan) or variations in the drilling and extraction activity over time that are too small (Uintah, Upper Green River).