Analysis of Airborne Infrared Measurements to Estimate Localized Methane Emissions

Kurzfassung

Methane is an essential atmospheric gas representing one fifth of the whole radiative forcing gases. The understanding of the behavior of methane is crucial for studying the climate change. Atmospheric methane concentration evolution through the last decades demonstrates a steady increasing trend and industrial sources of this gas, e.g. methane shafts are one of the sources of emissions into the atmosphere. Aims. To make an analysis of the airborne Hyper Spectral camera (HySpex) infrared measurements over one of the largest methane sources in Europe – Upper-Silesian region in Poland in order to estimate localized emissions. Methods. Four methods were introduced in this thesis based on the ratios and differences of the radiances from different wavenumber intervals. The focus of the work was concentrated at the methane absorption interval in short-wave infrared range (around 6000 cm -1 or 1.6 μm). Besides this, least-squares methods were used to estimate geophysical state parameters, i.e. ground albedo values and methane abundance enhancements from the observed data. Results. One out of four presented methods show the presence of the methane plume over one of the sensed shafts from the various measurement altitudes: 1520 m and 2900 m. Moreover, two more weak methane sources were detected over another shaft. Comparison between the outputs of simulations with different changing parameters were done, e.g. different molecular absorption line parameter databases, diverse altitudes for the top of atmosphere (ToA) selection, divergent type of atmospheric datasets, distinct empirical albedo types, various water concentrations in the atmosphere etc. Finally, the contour plots with least-squares fitted albedo values and methane scaling factor over one of the detected plumes were demonstrated. Conclusions. This work has shown the ability of detecting methane plume with an airborne sensor with high spatial (1.4 m), but low spectral (4.75 nm) resolution. One of the suggested methods can detect plumes with ~10-20 meters wide. Comparing the results of this thesis with the outcomes of other authors who also used the HySpex family of airborne sensor for methane plume detection, but with a totally different processing approach, one can conclude that the accuracy of the outputs in both cases is comparable. Also, there is a big field for further improvements that are mentioned in this work.