Development And Improvement Of Spectroscopic Techniques For Atmospheric Composition Measurements From Ground And Space

Investigating the role of the atmosphere in climate change requires a large body of observations and measurements of atmospheric composition. This requires the development of observational techniques and instrumentation, as well as modeling and methods for the correction of past measurements. Some of the more important atmospheric components that contribute significantly to climate change are ozone, methane, carbon dioxide and water vapour. The effect of the changes in these elements is more prominent in the Arctic region. In the Arctic, changes in greenhouse gas amounts can have amplified effects through their indirect impact on surface albedo, humidity, ocean currents and temperature. This thesis focuses on investigating improvements of ozone measurements and the development of spectroscopic techniques and instrumentation to measure carbon dioxide, methane and the oxygen A-band in the arctic atmosphere. The first section of this thesis focuses on retrieval methods and analyzing data produced by the Brewer Spectrophotometer. Stray light in the Brewer instrument causes an underestimation of daily ozone values especially in the northern latitudes where, at certain times of the year, measurements must be made at large solar zenith angles. This section focuses on a practical method to correct for stray light effects that includes a mathematical model of the instrument response and a non-linear retrieval approach that calculates the best values for the model parameters. In the second section, new instrumentation designed and developed to measure atmospheric mixing ratios of methane, carbon dioxide and the oxygen A-band is reported. This instrument, an imaging Fourier Transform Spectrometer (IFTS), is one of the first of its kind to be built. It is a next-generation, atmospheric measurement instrument that can provide high spatial resolution and continuous observations of the Arctic. This thesis will describe the optical and mechanical design of the payload, including the fore-optics that includes an image stabilizer. The system design is also described, which involves instrument characterization, electronic interfaces, software interfaces, data storage and handling, testing the payload in a lab setting and data analysis methods.