@article{MacdonaldOteroButler2021, author = {Macdonald, Elena and Otero, Noelia and Butler, Tim}, title = {A comparison of long-term trends in observations and emission inventories of NOx}, series = {Atmospheric chemistry and physics / European Geosciences Union}, volume = {21}, journal = {Atmospheric chemistry and physics / European Geosciences Union}, number = {5}, publisher = {Copernicus}, address = {G{\"o}ttingen}, issn = {1680-7316}, doi = {10.5194/acp-21-4007-2021}, pages = {4007 -- 4023}, year = {2021}, abstract = {Air pollution is a pressing issue that is associated with adverse effects on human health, ecosystems, and climate. Despite many years of effort to improve air quality, nitrogen dioxide (NO2) limit values are still regularly exceeded in Europe, particularly in cities and along streets. This study explores how concentrations of nitrogen oxides (NOx = NO + NO2) in European urban areas have changed over the last decades and how this relates to changes in emissions. To do so, the incremental approach was used, comparing urban increments (i.e. urban background minus rural concentrations) to total emissions, and roadside increments (i.e. urban roadside concentrations minus urban background concentrations) to traffic emissions. In total, nine European cities were assessed. The study revealed that potentially confounding factors like the impact of urban pollution at rural monitoring sites through atmospheric transport are generally negligible for NOx. The approach proves therefore particularly useful for this pollutant. The estimated urban increments all showed downward trends, and for the majority of the cities the trends aligned well with the total emissions. However, it was found that factors like a very densely populated surrounding or local emission sources in the rural area such as shipping traffic on inland waterways restrict the application of the approach for some cities. The roadside increments showed an overall very diverse picture in their absolute values and trends and also in their relation to traffic emissions. This variability and the discrepancies between roadside increments and emissions could be attributed to a combination of local influencing factors at the street level and different aspects introducing inaccuracies to the trends of the emis-sion inventories used, including deficient emission factors. Applying the incremental approach was evaluated as useful for long-term pan-European studies, but at the same time it was found to be restricted to certain regions and cities due to data availability issues. The results also highlight that using emission inventories for the prediction of future health impacts and compliance with limit values needs to consider the distinct variability in the concentrations not only across but also within cities.}, language = {en} } @masterthesis{Macdonald2017, type = {Bachelor Thesis}, author = {Macdonald, Elena}, title = {Stable isotopes in precipitation: Modelling intra-event variations using meteorological parameters}, doi = {10.25932/publishup-50661}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-506612}, school = {Universit{\"a}t Potsdam}, pages = {32}, year = {2017}, abstract = {Die kurzfristige Variabilit{\"a}t der Isotopenzusammensetzung von Niederschl{\"a}gen in Golm, Deutschland wurde untersucht und modelliert. Daf{\"u}r wurden Isotopendaten (D/H und 18O/16O) mit einer hohen zeitlichen Aufl{\"o}sung sowie meteorologische Daten von einer Wetterstation und einem Mikroregenradar genutzt. Nach der Datenaufbereitung und dem Zusammenf{\"u}hren aller drei Datens{\"a}tze wurde eine multivariate lineare Regressionsanalyse durchgef{\"u}hrt. Dies geschah f{\"u}r vier verschiedene, auf den Isotopendaten beruhende Response-Variablen und f{\"u}r den gesamten Datensatz sowie f{\"u}r die zwei Teildatens{\"a}tze Sommer und Winter. Die verwendeten Response-Variablen sind die Differenzen der δ18O-Werte zu den ereignisbasierten Mittel- und Medianwerten und die Differenzen der Deuterium-Exzess-Werte zu den ereignisbasierten Mittel- und Medianwerten. F{\"u}r die erhaltenen Modelle wurden die modellierten Werte mit den gemessenen Werten verglichen, wobei sich herausstellte, dass die Messwerte nicht zufriedenstellend wiedergegeben werden konnten. Daher werden am Ende mehrere Vorschl{\"a}ge gemacht, wie das Vorgehen und damit auch das Ergebnis der Modellierung m{\"o}glicherweise verbessert werden kann.}, language = {en} } @article{MerzBassoFischeretal.2022, author = {Merz, Bruno and Basso, Stefano and Fischer, Svenja and Lun, David and Bloeschl, Guenter and Merz, Ralf and Guse, Bjorn and Viglione, Alberto and Vorogushyn, Sergiy and Macdonald, Elena and Wietzke, Luzie and Schumann, Andreas}, title = {Understanding heavy tails of flood peak distributions}, series = {Water resources research}, volume = {58}, journal = {Water resources research}, number = {6}, publisher = {American Geophysical Union}, address = {Washington}, issn = {0043-1397}, doi = {10.1029/2021WR030506}, pages = {37}, year = {2022}, abstract = {Statistical distributions of flood peak discharge often show heavy tail behavior, that is, extreme floods are more likely to occur than would be predicted by commonly used distributions that have exponential asymptotic behavior. This heavy tail behavior may surprise flood managers and citizens, as human intuition tends to expect light tail behavior, and the heaviness of the tails is very difficult to predict, which may lead to unnecessarily high flood damage. Despite its high importance, the literature on the heavy tail behavior of flood distributions is rather fragmented. In this review, we provide a coherent overview of the processes causing heavy flood tails and the implications for science and practice. Specifically, we propose nine hypotheses on the mechanisms causing heavy tails in flood peak distributions related to processes in the atmosphere, the catchment, and the river system. We then discuss to which extent the current knowledge supports or contradicts these hypotheses. We also discuss the statistical conditions for the emergence of heavy tail behavior based on derived distribution theory and relate them to the hypotheses and flood generation mechanisms. We review the degree to which the heaviness of the tails can be predicted from process knowledge and data. Finally, we recommend further research toward testing the hypotheses and improving the prediction of heavy tails.}, language = {en} } @article{MacdonaldMerzGuseetal.2022, author = {Macdonald, Elena and Merz, Bruno and Guse, Bj{\"o}rn and Wietzke, Luzie and Ullrich, Sophie and Kemter, Matthias and Ahrens, Bodo and Vorogushyn, Sergiy}, title = {Event and catchment controls of heavy tail behavior of floods}, series = {Water resources research}, volume = {58}, journal = {Water resources research}, number = {6}, publisher = {American Geophysical Union}, address = {Washington}, issn = {0043-1397}, doi = {10.1029/2021WR031260}, pages = {25}, year = {2022}, abstract = {In some catchments, the distribution of annual maximum streamflow shows heavy tail behavior, meaning the occurrence probability of extreme events is higher than if the upper tail decayed exponentially. Neglecting heavy tail behavior can lead to an underestimation of the likelihood of extreme floods and the associated risk. Partly contradictory results regarding the controls of heavy tail behavior exist in the literature and the knowledge is still very dispersed and limited. To better understand the drivers, we analyze the upper tail behavior and its controls for 480 catchments in Germany and Austria over a period of more than 50 years. The catchments span from quickly reacting mountain catchments to large lowland catchments, allowing for general conclusions. We compile a wide range of event and catchment characteristics and investigate their association with an indicator of the tail heaviness of flood distributions, namely the shape parameter of the GEV distribution. Following univariate analyses of these characteristics, along with an evaluation of different aggregations of event characteristics, multiple linear regression models, as well as random forests, are constructed. A novel slope indicator, which represents the relation between the return period of flood peaks and event characteristics, captures the controls of heavy tails best. Variables describing the catchment response are found to dominate the heavy tail behavior, followed by event precipitation, flood seasonality, and catchment size. The pre-event moisture state in a catchment has no relevant impact on the tail heaviness even though it does influence flood magnitudes.}, language = {en} }