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The focus of this study were Celtic gold coins excavated from the Martberg, a Celtic oppidium and sanctuary, occupied in the first century B.C. by a Celtic tribe known as the Treveri. These coins and a number of associated coinages, were characterised in terms of their alloy compositions and their geochemical and isotopic signatures so as to answer archaeological and numismatic questions of coinage development and metal sources. This required the development of analytical methods involving; Electron Microprobe (EPMA), Laser Ablation-ICP-MS, solution Multicollector-ICPMS and LA-MC-ICP-MS. The alloy compositions (Au-Ag-Cu-Sn) were determined by EPMA on a small polished area on the edge of the coins. A large beam size, 50µm (diameter), was used to overcome the extreme heterogeneity of these alloys. These analyses were shown to be representative of the bulk composition of the coins. The metallurgical development of the coinages was defined and showed that the earlier coinages followed a debasement trend, which was superceded by a trend of increasing copper at the expense of sliver while gold compositions remained stable. This change occurred with the appearance of the inscribed "POTTINA" coinage, Scheers 30/V. Two typologically different coinages, Scheers 16 and 18 ("Armorican Types") were found to have markedly different compositions which do not fit into the trends described above. A Flan for a gold coin, which may indicate the presence of a mint at the Martberg, was found to have an identicle weight and composition as the Scheers 30/I coins, which preceeded the majority of the coins found at the Martberg in the coin development chronology. The trace element anaylses were made by Laser Ablation-ICPMS using an AridusTM desolvating nebuliser to introduce matrix matched solution standards to calibrate the measurements, which were then normalised to 100%. Quantitative results were obtained for the following elements: Sc, Ti, Cr, Mn, Co, Ni, Cu, Zn, Se, Ru, Rh, Pd, Ag, Sb, Te, W, Ir, Pt, Pb, Bi. The remaining elements remain problematic as they produced incorrect standardisations mainly due to chemical effects in solution such as adsorption onto the beaker walls or oxidation : V, Fe, Ga, Ge, As, Mo, Sn, Re, Os, Hg. Changes in the sources of Au, Ag and Cu were observed during the development of the coinages through the variation of trace elements, which correlate positively with the major components of the coin alloys. Changes in the Pt/Au ratios show that the Scheers 23 coins contain distinctly different gold from the later coinages and that the Scheers 18 gold source was also different. Te/Ag was used to show that the Sch.23 coins also contained different silver and some subgroups were observed in the Sch. 30/V coins. A major change in copper source is indicated by the sudden increase of Sb and Ni with the introduction of the Sch. 30/V coins (POTTINA), which can be linked to a similar change in copper observed in the contemporary silver coinage, Sch. 55 (with a ring). Lead isotopic analyses were made by solution- and Laser Ablation - MC-ICP-MS, The laser technique proved to be in good agreement with the solution analyses with precisions between 1 and 0.1%o (per mil). The development of the laser method opens the way for easy and virtually non-destructive Pb isotopic determinations of ancient gold coins. The results showed that Sch. 23 is very different from the following coinages, Sch. 16 and 18 are also different, forming their own group, and all the later "Eye" staters (Sch. 30/I-VI) lie on a mixing line controlled by the addition of copper from a Mediterranean source, probably Sardinia or Spain. An indication of gold and silver sources should be possible with further analyses of the Sch. 23 and Rainbow Cup gold coins and the Sch. 54 and 55 silver coinages. Copper Isotopic analyses were made by solution- and Laser Ablation - MC-ICP-MS. Both techniques require further development to produce more reproducible results. The results show that there appears to be a trend to more positive d Cu65 values for the later coinages and that the link between the copper used in the Sch. 30/V (POTTINA) coins and the silver Sch. 55 (with a ring) coins is also shown by similarly postive d Cu65 values. The full suite of analyses were also made on samples of gold from the region. They were mostly composed of "placer gold", alluvial gold found in rivers. It was found that when a study is restricted to a limited number of deposits or areas then it is possible to distinguish between deposits based on the concentration of those elements which are least affected by transport related alteration processes. These elements include; the PGE's, due to their refractory nature, and those elements which are usually present in high enough concentrations to remain relatively unaffected, eg: Cu, Pb and Sb. Due to the nature of the coin alloy it is not possible to link the gold used in the coins studied here with gold deposits, as the large amounts of Ag and Cu, added to the coin alloys, have masked the Au signature. However, further Pb isotopic analyses of gold deposits should prove useful in determining from which regions Celtic gold was derived.
Measurements of OH, total peroxy radicals, non-methane hydrocarbons (NMHCs) and various other trace gases were made at the Meteorological Observatory Hohenpeissenberg in June 2000. The data from an intensive measurement period characterised by high solar insolation (18-21 June) are analysed. The maximum midday OH concentration ranged between 4.5x106 molecules cm-3 and 7.4x106 molecules cm-3. The maximum total ROx (ROx =OH+RO+HO2+RO2) mixing ratio increased from about 55 pptv on 18 June to nearly 70 pptv on 20 and 21 June. A total of 64 NMHCs, including isoprene and monoterpenes, were measured every 1 to 6 hours. The oxidation rate of the NMHCs by OH was calculated and reached a total of over 14x106 molecules cm-3 s-1 on two days. A simple photostationary state balance model was used to simulate the ambient OH and peroxy radical concentrations with the measured data as input. This approach was able to reproduce the main features of the diurnal profiles of both OH and peroxy radicals. The balance equations were used to test the effect of the assumptions made in this model. The results proved to be most sensitive to assumptions about the impact of unmeasured volatile organic compounds (VOC), e.g. formaldehyde (HCHO), and about the partitioning between HO2 and RO2. The measured OH concentration and peroxy radical mixing ratios were reproduced well by assuming the presence of 3 ppbv HCHO as a proxy for oxygenated hydrocarbons, and a HO2/ RO2 ratio between 1:1 and 1:2. The most important source of OH, and conversely the greatest sink for peroxy radicals, was the recycling of HO2 radicals to OH. This reaction was responsible for the recycling of more than 45x106 molecules cm-3 s-1 on two days. The most important sink for OH, and the largest source of peroxy radicals, was the oxidation of NMHCs, in particular, of isoprene and the monoterpenes.
Mechanisms by which subvisible cirrus clouds (SVCs) might contribute to dehydration close to the tropical tropopause are not well understood. Recently Ultrathin Tropical Tropopause Clouds (UTTCs) with optical depths around 10-4 have been detected in the western Indian ocean. These clouds cover thousands of square kilometers as 200-300 m thick distinct and homogeneous layer just below the tropical tropopause. In their condensed phase UTTCs contain only 1-5% of the total water, and essentially no nitric acid. A new cloud stabilization mechanism is required to explain this small fraction of the condensed water content in the clouds and their small vertical thickness. This work suggests a mechanism, which forces the particles into a thin layer, based on upwelling of the air of some mm/s to balance the ice particles, supersaturation with respect to ice above and subsaturation below the UTTC. In situ measurements suggest that these requirements are fulfilled. The basic physical properties of this mechanism are explored by means of a single particle model. Comprehensive 1-D cloud simulations demonstrate this stabilization mechanism to be robust against rapid temperature fluctuations of +/- 0.5 K. However, rapid warming (Delta T > 2 K) leads to evaporation of the UTTC, while rapid cooling (Delta T < -2 K) leads to destabilization of the particles with the potential for significant dehydration below the cloud
Mechanisms by which subvisible cirrus clouds (SVCs) might contribute to dehydration close to the tropical tropopause are not well understood. Recently Ultrathin Tropical Tropopause Clouds (UTTCs) with optical depths around 10−4 have been detected in the western Indian ocean. These clouds cover thousands of square kilometers as 200–300 m thick distinct and homogeneous layer just below the tropical tropopause. In their condensed phase UTTCs contain only 1–5% of the total water, and essentially no nitric acid. A new cloud stabilization mechanism is required to explain this small fraction of the condensed water content in the clouds and their small vertical thickness. This work suggests a mechanism, which forces the particles into a thin layer, based on upwelling of the air of some mm/s to balance the ice particles, supersaturation with respect to ice above and subsaturation below the UTTC. In situ measurements suggest that these requirements are fulfilled. The basic physical properties of this mechanism are explored by means of a single particle model. Comprehensive 1-D cloud simulations demonstrate this stabilization mechanism to be robust against rapid temperature fluctuations of +/−0.5 K. However, rapid warming (ΔT>2 K) leads to evaporation of the UTTC, while rapid cooling (ΔT<−2 K) leads to destabilization of the particles with the potential for significant dehydration below the cloud.
Subvisible cirrus clouds (SVCs) may contribute to dehydration close to the tropical tropopause. The higher and colder SVCs and the larger their ice crystals, the more likely they represent the last efficient point of contact of the gas phase with the ice phase and, hence, the last dehydrating step, before the air enters the stratosphere. The first simultaneous in situ and remote sensing measurements of SVCs were taken during the APE-THESEO campaign in the western Indian ocean in February/March 1999. The observed clouds, termed Ultrathin Tropical Tropopause Clouds (UTTCs), belong to the geometrically and optically thinnest large-scale clouds in the Earth's atmosphere. Individual UTTCs may exist for many hours as an only 200–300 m thick cloud layer just a few hundred meters below the tropical cold point tropopause, covering up to 105 km2. With temperatures as low as 181 K these clouds are prime representatives for defining the water mixing ratio of air entering the lower stratosphere.
Subvisible cirrus clouds (SVCs) may contribute to dehydration close to the tropical tropopause. The higher and colder SVCs and the larger their ice crystals, the more likely they represent the last efficient point of contact of the gas phase with the ice phase and, hence, the last dehydrating step, before the air enters the stratosphere. The first simultaneous in situ and remote sensing measurements of SVCs were taken during the APE-THESEO campaign in the western Indian ocean in February/March 1999. The observed clouds, termed Ultrathin Tropical Tropopause Clouds (UTTCs), belong to the geometrically and optically thinnest large-scale clouds in the Earth´s atmosphere. Individual UTTCs may exist for many hours as an only 200--300 m thick cloud layer just a few hundred meters below the tropical cold point tropopause, covering up to 105 km2. With temperatures as low as 181 K these clouds are prime representatives for defining the water mixing ratio of air entering the lower stratosphere.
We report measurements of the deuterium content of molecular hydrogen (H2) obtained from a suite of air samples that were collected during a stratospheric balloon flight between 12 and 33 km at 40º N in October 2002. Strong deuterium enrichments of up to 400 permil versus Vienna Standard Mean Ocean Water (VSMOW) are observed, while the H2 mixing ratio remains virtually constant. Thus, as hydrogen is processed through the H2 reservoir in the stratosphere, deuterium is accumulated in H2 . Using box model calculations we investigated the effects of H2 sources and sinks on the stratospheric enrichments. Results show that considerable isotope enrichments in the production of H2 from CH4 must take place, i.e., deuterium is transferred preferentially to H2 during the CH4 oxidation sequence. This supports recent conclusions from tropospheric H2 isotope measurements which show that H2 produced photochemically from CH4 and non-methane hydrocarbons must be enriched in deuterium to balance the tropospheric hydrogen isotope budget. In the absence of further data on isotope fractionations in the individual reaction steps of the CH4 oxidation sequence, this effect cannot be investigated further at present. Our measurements imply that molecular hydrogen has to be taken into account when the hydrogen isotope budget in the stratosphere is investigated.
Temporal changes in the occurrence of extreme events in time series of observed precipitation are investigated. The analysis is based on a European gridded data set and a German station-based data set of recent monthly totals (1896=1899–1995=1998). Two approaches are used. First, values above certain defined thresholds are counted for the first and second halves of the observation period. In the second step time series components, such as trends, are removed to obtain a deeper insight into the causes of the observed changes. As an example, this technique is applied to the time series of the German station Eppenrod. It arises that most of the events concern extreme wet months whose frequency has significantly increased in winter. Whereas on the European scale the other seasons also show this increase, especially in autumn, in Germany an insignificant decrease in the summer and autumn seasons is found. Moreover it is demonstrated that the increase of extreme wet months is reflected in a systematic increase in the variance and the Weibull probability density function parameters, respectively.
Observed global and European spatiotemporal related fields of surface air temperature, mean-sea-level pressure and precipitation are analyzed statistically with respect to their response to external forcing factors such as anthropogenic greenhouse gases, anthropogenic sulfate aerosol, solar variations and explosive volcanism, and known internal climate mechanisms such as the El Niño-Southern Oscillation (ENSO) and the North Atlantic Oscillation (NAO). As a first step, a principal component analysis (PCA) is applied to the observed spatiotemporal related fields to obtain spatial patterns with linear independent temporal structure. In a second step, the time series of each of the spatial patterns is subject to a stepwise regression analysis in order to separate it into signals of the external forcing factors and internal climate mechanisms as listed above as well as the residuals. Finally a back-transformation leads to the spatiotemporally related patterns of all these signals being intercompared. Two kinds of significance tests are applied to the anthropogenic signals. First, it is tested whether the anthropogenic signal is significant compared with the complete residual variance including natural variability. This test answers the question whether a significant anthropogenic climate change is visible in the observed data. As a second test the anthropogenic signal is tested with respect to the climate noise component only. This test answers the question whether the anthropogenic signal is significant among others in the observed data. Using both tests, regions can be specified where the anthropogenic influence is visible (second test) and regions where the anthropogenic influence has already significantly changed climate (first test).
In dieser Arbeit wurde der chemische Ozonverlust in der arktischen Stratosphäre über elf Jahre hinweg, zwischen 1991 und 2002, mit Hilfe der so genannten "Ozon-Tracer Korrelationstechnik" (TRAC), untersucht. Bei dieser Methode werden Korrelationen zwischen Ozon und langlebigen Spurenstoffen im Verlauf des Winters im Polarwirbels beobachtet und so der jährliche akkumulierte Ozonverlust berechnet. Die Ergebnisse dieser Arbeit basieren im wesentlichen auf Messdaten der Satelliteninstrumente: HALOE (Halogen Occultation Experiment) auf UARS (Upper Atmosphere Research Satellite) und ILAS (Improved Limb Atmospheric Spectrometer) Instrument auf ADEOS (Advanced Earth Observing Satellite). Das HALOE Instrument misst seit Oktober 1991 kontinuierlich alle zwei bis drei Monate für einige Tage in höheren nördlichen Breiten. ILAS lieferte ausschließlich für den Winter 1996-97 Messungen, die über sieben Monate hinweg in hohen Breiten aufgenommen wurden. Aufgrund der eingeführten Erweiterungen und Verbesserungen der Methode in dieser Arbeit, konnte die Methode anhand einer detaillierten Studie für den Winter 1996-97 validiert werden. Die ILAS Messreihe wurde dazu verwendet, erstmals die Untersuchung der zeitlichen Entwicklung von Ozon-Tracer Korrelationen kontinuierlich für die gesamte Lebensdauer des Polarwirbels durchzuführen. Dabei wurden auch Korrelationen während der Bildung des Wirbels untersucht und im Besonderen mögliche Mischungsvorgänge zwischen Wirbelluft und Luftmassen außerhalb des Wirbels. Ausserdem wurde ein Vergleich der Ergebnisse von ILAS und HALOE Messdaten durchgeführt und Unterschiede in den Ergebnissen tiefgreifend analysiert. Basierend auf HALOE Messungen konnte die erweiterte TRAC Methode über elf Jahren hinweg angewendet werden. Damit war erstmals eine konsistente Analyse von Ozonverlust und Chloraktivierung über diesen Zeitraum möglich. Die Erweiterungen führten zu einer Verringerung und genauen Quantifizierung von Unsicherheiten der Ergebnisse. Ein deutlicher Zusammenhang zwischen meteorologischen Bedingungen, Chloraktivierung und dem chemischen Ozonverlust wurde deutlich. Weiterhin zeigte sich eine Abhängigkeit zwischen den meteorologischen Bedingungen und der Homogenität des Ozonverlustes innerhalb eines Winters, sowie der mögliche Einfluss von horizontaler Mischung auf Luftmassen in einem schwach ausgeprägten Polarwirbel. In dieser Arbeit wurde eine positive Korrelation zwischen den über die gesamte Lebensdauer des Wirbels auftretenden möglichen PSC-Flächen und den akkumulierten Ozonverlusten für die elf untersuchten Jahre deutlich. Es konnte darüber hinaus gezeigt werden, dass der Ozonverlust von deutlich mehr Einflüssen als nur von der Fläche möglichen PSC Auftretens bestimmt wird, sondern zum Beispiel von der Stärke der Sonneneinstrahlung abhängt. Außerdem lassen sich Auswirkungen von Vulkanausbrüchen, wie zum Beispiel im Jahr 1991 der des Mount Pinatubo, identifizieren.