Advanced Analysis Techniques And Deep Learning For Atmospheric Measurements

This work explores a wide range of data analysis and signal processing methods for different possible applications in atmospheric measurements. While these methods and applications span a wide area of disciplines, the evaluation of applicability and limitations and the results of this evaluation show many similarities. In the first study, a new framework for the temporal characterization of airborne atmospheric measurement instruments is provided. Allan-Werle-plots are applied to quantify dominant noise structures present in the time series. Their effects on the drift correction capabilities and measurement uncertainty estimation can be evaluated via simulation. This framework is applied to test flights of an airborne field campaign and reveals an appropriate interval between calibration measurements of 30 minutes. During ground operation, the drift correction is able to reduce the measurement uncertainty from 1.1% to 0.2 %. Additional short-term disturbances during airborne operation increase the measurement uncertainty to 1.5 %. In the second study, the applicability and limitations of several noise reduction methods are tested for different background characteristics. The increase in signal-noiseratio and the added bias strongly depend on the background structure. Individual regions of applicability show almost no overlap for the different noise reduction methods. In the third study, a fast and versatile Bayesian method called sequential Monte Carlo filter is explored for several applications in atmospheric field experiments. This algorithm combines information provided via the measurements with prior information from the dominant chemical reactions. Under most conditions the method shows potential for precision enhancement, data coverage increase and extrapolation. Limitations are observed that can be analyzed via the entropy measure and improvements are achieved via the extension by an additional activity parameter. In the final study, state-of-the-art neural network architectures and appropriate data representations are used to reduce the effect of interference fringes in absorption spectroscopy. Using the neural network models as an alternative to linear fitting yields a large bias which renders the model approach not applicable. On the task of background interpolation the neural network approach shows robust de-noising behavior and is shown to be transferable to a different absorption spectrometer setup. Application of the interpolation to the test set lowers the detection limit by 52%. This work highlights the importance of in-depth analysis of the effects and limitations of advanced data analysis techniques to prevent biases and data artifacts and to determine the expected data quality improvements. An elaboration of the limitations is particularly important for deep learning applications. All presented studies show great potential for further applications in atmospheric measurements.