Ein neues C02-Parametrisierungsschema, das variable CO2-Konzentrationen im gesamten Höhenbereich von 15 - 150 km zuläßt, wurde in das Kölner Zirkulationsmodell der mittleren Atmosphäre (COMMA) implementiert und der Einfluß einer C02-Erhöhung im Bereich von 10% - 100% auf die Zirkulation der mittleren Atmosphäre untersucht. Die C02-Erhöhung bewirkt eine starke Abkühlung der gesamten mittleren Atmosphäre von 20 km bis zum oberen Modellrand mit Maximalwerten von 20 K in der Stratopause und höheren Werten in der unteren Thermosphäre bei CO2-Verdoppelung. Weiterhin wird eine starke Dämpfung der halbtägigen Gezeitenamplitude beobachtet, die das mittlere Windfeld und die Meridionalzirkulation in der Mesosphäre und unteren Thermosphäre durch die Abnahme der Impulsablagerung aus den brechenden Gezeiten modifiziert. Die stärkste Dämpfung zeigt sich im Bereich niederer Breiten der Nord- und Südhemisphäre. Langzeitwindmessungen in der Mesopausenregion bestätigen den abnehmenden Trend der halbtägigen Gezeit. Daraus folgt, daß dieser Trend wahrscheinlich eine Folge der anthropogenen C02-Emission sind. / Using a state of the art C02 parametrization scheme for the middle atmosphere with variable C02 concentration, a comprehensive model study on C02 increase ranging from 10% - 100% above the present concentration has been performed. Strong cooling is present throughout the middle atmosphere from 20 km up to the top of the model domain with maximum values of about 20 K in the stratopause and even higher values in the lower thermosphere for the double C02 case. Besides this, damping of the semidiurnal tide modifies the mean wind field in the mesosphere/lower thermosphere region by weaker deposition of momentum from tidal breakdown. Strongest damping appears in the low latitude region. Long term midlatitude wind measurements in the mesopause region confirm these model results. Therefore the decrease of the semidiurnal amplitude is probably due to anthropogenic C02 emission.

Trace gas (CO2 and its carbon and oxygen isotopes, CH4, CO, H2 and N2O) vertical profile data above Cape Grim, Tasmania for the period April 1992 to February 1997 are investigated. A climatology of the distribution of each trace gas has been compiled from statistical treatment of the raw data. These climatologies are useful for verification of transport model outputs. Here, the CO2 climatology is compared to simulation results from two transport models (Melbourne University Transport Model and TM2Z) using three different sets of CO2 fluxes separately (compiled with different methods by different authors). Large discrepancies are found between simulations and observations, especially in the free troposphere (4-6 km). By considering emission ratios, trajectories, satellite fire counts and simulation with biomass burning fluxes, the influence of tropical biomass burning plumes on the southeastern Australian region in the austral winter/spring is studied and quantified. This identification process requires a multiple-species approach where the large CO anomalies and the unexpected behaviour of H2 are most revealing. The frequent presence of burning plumes in the mid troposphere complicates one of the original motivations for the Cape Grim Overflight Program, which is to estimate the air-sea exchange of CO2 in this region. A suggestion arising from analysis of pre-1992 aircraft sampling in this region was that the regional CO2 air-sea flux south of Australia is exceptionally large.

Cement production is responsible for around 7% of the global anthropogenic carbon dioxide emissions. More than half of these emissions are due to the unavoidable release of carbon dioxide upon thermal decomposition of the main raw material limestone. Many different options for carbon capture are currently being investigated to lower emissions, and one potential route to facilitate carbon capture could be the implementation of an electrified separate calcination step. However, potential effects on the phase composition of cement clinker need to be investigated, which is the aim of the present study. Phases of special interest are alite, belite, aluminate, ferrite, calcite, and lime.  The phase composition during clinker formation was examined through HT-XRD lab-scale experiments, allowing the phase transformations to be observed in situ. Two different methods of separate calcination were investigated, one method in which the raw meal was calcined separately, and one method where the limestone was calcined separately. The former yielded an alite amount similar to that of the reference experiments, whereas the latter method yielded a lower amount. It could, unfortunately, not be excluded that the difference was due to poor experimental conditions, and additional experiments are needed to investigate the matter further. The study does, however, indicate that a calcined raw meal might be used to produce a clinker of similar phase composition concerning major phases belite, aluminate, ferrite, alite, and free lime. A raw meal containing calcined limestone might, however, need longer residence time at clinkering temperature too obtain similar phase composition. In addition, a raw meal containing calcined limestone was observed to be carbonated to a greater extent upon reheating than a calcined raw meal. Further experiments are needed to fully understand the effects on clinker composition of an electrified separate calcination step, and several improvements to the experimental method are given in the study.