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Benzenesulfonates, para-substituted with amine, chloride and methyl groups were successfully incorporated into layered double hydroxides of two different compositions, 2:1 Mg-Al LDH and 2:1 Zn-Al LDH. These parent materials were also doped with small amounts of nickel and the differences in the two systems were studied. The hexamethylenetetramine route of layered double hydroxide synthesis was investigated to verify if the mechanism is indeed homogeneous. This included attempting preparation of 2:1 Mg-Al LDH, 2:1 Zn-Al LDH and 2:1 Zn-Cr LDH with two different concentrations of hexamethylenetetramine. The analytical data of the products suggest that the homogeneous precipitation may not be the true mechanism of reaction involved in LDH synthesis by this method.

This study uses airborne data from multiple field campaigns off the California coast to determine the extent to which a size distribution parameter and a cloud water chemical measurement can capture the effect of giant cloud condensation nuclei (GCCN), specifically sea salt, on marine stratocumulus cloud properties. The two GCCN proxy variables, near-surface particle number concentration for diameters >5 mu m and cloud water chloride concentration, are significantly correlated (95% confidence) with each other, and both exhibit expected relationships with other parameters (e.g., surface wind) that typically coincide with sea salt emissions. Factors influencing the relationship between these two GCCN proxy measurements include precipitation rate (R) and the standard deviation of the subcloud vertical velocity owing likely to scavenging effects and improved mixing/transport of sea salt to cloud base, respectively. When comparing 12 pairs of high and low chloride cloud cases (at fixed liquid water path and cloud drop number concentration), the average drop spectra for high chloride cases exhibit enhanced drop number at diameters exceeding 20 mu m, especially above 30 mu m. In addition, high chloride cases coincide with enhanced mean columnar R and negative values of precipitation susceptibility. The difference in drop effective radius between high and low chloride conditions decreases with height in cloud, suggesting that some GCCN-produced raindrops precipitate before reaching cloud tops. The sign of cloud responses (i.e., R) to perturbations in giant sea salt particle concentration, as evaluated from Modern Era Retrospective Analysis for Research and Applications version 2 reanalysis data, is consistent with the aircraft data.

This study investigates if the descent of odd nitrogen, generated in the thermosphere and the upper mesosphere by energetic particle precipitation (EPP-NOx), has a detectable impact on stratospheric wind and temperature in late winter and spring presumably through the loss of ozone and reduction of absorption of solar UV. In both hemispheres, similar downward propagating geomagnetic signals in the extratropical stratosphere are found in spring for those years when no stratospheric sudden warming occurred in mid-winter. Anomalous easterly winds and warmer polar regions are found when the 4-month averaged winter Ap index (Ap) is high, and the signals become clearer when solar F10.7 is low. In May, significant geomagnetic signals are obtained in the Northern Hemisphere when the data are grouped according to the phase of the stratospheric equatorial QBO. The magnitudes of changes in spring stratospheric wind and temperatures associated with Ap signals are in the range of 10–20 m s−1 and 5–10 K, which are comparable with those of the 11-yr SC signals typically found in late winter. The spring Ap signals show the opposite sign to that expected due to in situ cooling effects caused by catalytic destruction of stratospheric ozone by descending EPP-NOx. Thus it is unlikely that the in situ chemical effect of descending EPP-NOx on stratospheric ozone would have a dominant influence on stratospheric circulation. Instead, we suggest that the detected Ap signals in the extratropical spring stratosphere may be an indirect consequence of geomagnetic and solar activity, dynamically induced by changes in wave ducting conditions.

In dieser Arbeit werden verfügbare Normalwerte (Zeitraum 1951 bis 1980) aufbereitet und eine Karte der mittleren jährlichen Niederschlagssummen für den Raum Leipzig entwickelt. Darüber hinaus erfolgen spezielle Auswertungen der in den Jahren 1992 bis 1998 an drei Standorten durchgeführten zehnrninütlichen Niederschlags- und Windmessungen. Niederschlags-Windrosen und Häufigkeitsverteilungen der Niederschlagsintensitäten werden gezeigt und diskutiert. / In this work available normal values (period 1951 to 1980) are edited and a card of the middle annual precipitation totals for the area of Leipzig is developed. In the another part of this study the ten minutes measurements of precipitation and wind from three stations in Leipzig in the years 1992 to 1998 are analysed. Precipitation wind-roses and frequency distributions of rain intensities are shown and discussed.

Die Modellierung eng begrenzter konvektiver Starkniederschlagsgebiete mit mesoskaligen numerischen Wettervorhersagemodellen ist durch die enorme Bandbreite der möglichen Zellverteilungen stets auf eine bestimmte Problemstellung beschränkt. Zahlreiche Autoren haben sich der Untersuchung superzellulärer Strukturen mithilfe idealisierter Strömungssimulationen gewidmet, um deren Entwicklung in unterschiedlichen atmosphärischen Umgebungen zu beschreiben (Atkins et al., 1999, Bluestein & Weisman, 2000, unter anderen). Im vorliegenden Artikel wird die Sensitivität der simulierten Niederschlagsintensität in Bezug auf verfügbare Labilitätsenergie, Umgebungswindverhältnisse sowie Einfluss orografischer Erhebungen näher betrachtet. Das dazu verwendete LMK mit 2:8km Gitterweite wurde ohne eine parametrisierte Behandlung der konvektiven Prozesse betrieben. Die Modellergebnisse der Simulationen mit idealisierten Eingangsbedingungen werden mit denen einer Fallstudie eines konvektiven Starkniederschlagsereignisses am 16.06.2006 in Sachsen bewertet. / Due to the huge variety of possible cell distributions, the simulation of small-scale heavy convective precipitation events using mesoscale numerical weather prediction models is limited to a certain issue of investigation. Numerous authors addressed the examination of supercellular structures by idealized ow simulations to describe their behaviour under various atmospheric conditions (Atkins et al., 1999, Bluestein & Weisman, 2000, among others). The presented paper studies the sensitivity of simulated precipitation intensity in response to the available amount of instability, environmental wind speed and -shear as well as orographic in uences. For this purpose, the LMK model with 2:8km grid spacing has been applied without a parameterized treatment of convective processes. The model results of the simulations involving idealized initial conditions are reviewed related to a case study of a severe storm event in Saxony on June, 16th 2006.

This thesis concerns the investigation of radioisotopes as indicators for precipitation reactions. As a precipitate forms in the presence of a radioisotope, adsorption may take place on its surface. If this adsorption changes markedly at the stoichiometric point it will be possible to use this variation as an indicator for the reaction.

The purpose of this investigation is to reveal the effects of certain factors affecting adsorption on some specific precipitates. It is hoped that the choice of precipitate types will enable extension of the information gained here to other precipitates similar to those investigated.

Precipitates of a series of alkaline earth metal (barium and strontium) carbonates, chromates, phosphates, and sulfates were formed at high supersaturation by diffusion through silica hydrogel, agarose hydrogel, and the freshly developed agarosesilica mixed gels. The reaction vessels could be a small test tube, a recently designed standard micro slide cassette and a enlarged supercassette. Homogeneous nucleation is thought to have taken place, and particle development led to the formation of an unusual category of materials, known as Induced Morphology Crystal Aggregates [IMCA], at high pH under far-from-equilibrium conditions. Standard procedures were developed in order to produce homogeneous gels. Particle development led to characteristic style of pattern formation, which I have called monster, spiral, and flake. Among these IMCA, barium carbonate, chromate, and sulfate were moderately easy to grow. Barium phosphate was very difficult to grow as IMCA due to formation of poorly crystalline spherulites. IMCA of strontium carbonate, chromate and sulfate could be developed at high basic pH in the presence of silicate. Strontium carbonate sheet morphology displays a unique property, double internal layer structure, which was identified by backscattering electron imaging (BEI). Selected electron diffraction (SAD) revealed a new crystal phase which was called "Dentonite". Precipitate particles were isolated using a non-destructive isolation technique. Optical microscopy was widely used to examine particles in situ and scanning electron microscopy and X-ray dispersive energy (EDX) spectroscopy were applied to particles ex situ, together with ESCA for surface analysis. Growth patterns were found to be strongly dependent on pH. Other related pattern formation processes were also investigated including normal and dendritic structures, spherulitic structures and periodic pattern formation. Some interpretations were proposed in terms of mechanism. Chemical additive effects were examined experimentally in the calcium phosphate system. The effect of external ionic strength was investigated, and it was found that a certain concentration of sodium chloride (0.2 M) approximately equals a fraction of pH unit (-0.2).