Zur Umstellung der grossräumigen Zirkulation in der Stratosphäre

Zusammenfassung Aufgrund theoretischer Überlegungen wird gefolgert, daß die Umstellung der stratosphärischen Zirkulation in deren Heizfläche (Obergrenze der Ozonschicht) und zwar in Nähe des Pols ihren Ausgang nimmt und sich dann nach Süden und gleichzeitig auch nach oben und unten ausdehnt. Nur bei der Umstellung von der winterlichen Westoströmung zur sommerlichen Ostwestströmung greift die äquatoriale Ostströmung etwas nach Norden aus, so daß dieser Wechsel über die ganze Erdhalbkugel weniger Zeit in Anspruch nehmen dürfte als die nur vom Pol ausgehende Umstellung von Ostwest- auf Westostzirkulation. Die Ergebnisse zeitlich verschiedener Darstellung des mittleren Windprofiles der Stratosphäre über der Nordhalbkugel, gewonnen aus Radiosondenaufstiegen und aus Forschungsraketenmessungen, stimmen mit dem erhaltenen Bild überein.

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Summary On basis of the theoretical considerations it will be inferred that the change of stratospheric circulation starts in the heating levels (upper boundary of ozone layers) in the region of the pole, and then spreads southward and at the same time upward and downward. Only at the time of change from the winterly west-east flow to the summerly east-west flow does the equatorial east flow spread out somewhat toward the north. Thus this change probably takes less time to spread over the hemisphere than the change from east-west to west-east starting only at the pole. The results representing different periods of time of the average wind profile of the stratosphere over the northern hemisphere, received from radiosonde and research missile measurings, confirm the maintained picture.

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Diese Arbeit wurde unterstützt vom US Department of the Army, European Research Office, Frankfurt (Main) unter Kontrakt Nr. DA-91-591-EUC-1668 (OI-7330-61).     

Trends in eutrophication research and control

Eutrophication is the natural ageing process of lakes. It is characterized by a geologically slow shift from in-lake biological production driven by allochthonous (external to the water body) loading of nutrients, to production driven by autochthonous (in-lake) processes. This shift typically is accompanied by changes in species and biotic community composition, as an aquatic ecosystem is ultimately transformed into a terrestrial biome. However, this typically slow process can be greatly accelerated by human intervention in the natural biogeochemical cycling of nutrients within a watershed; the resulting cultural eutrophication can create conditions inimical to the continued use of the water body for human-driven economic purposes. Excessive algal and rooted plant growth, degraded water quality, extensive deoxygenation of the bottom water layers and increased fish biomass accompanied by decreased harvest quality, are some features of this process. Following the Second World War, concern with cultural eutrophication achieved an intensity that spurred a significant research effort, culminating in the identification of phosphorus as the single most significant, and controllable, element involved in driving the eutrophication process. During the late 1960s and throughout the 1970s, much effort was devoted to reducing phosphorus in wastewater effluents, primarily in the developed countries of the temperate zone. These efforts generally resulted in the control of eutrophication in these countries, albeit with varying degrees of success. The present effort in the temperature zone, comprising mostly developed nations, has now shifted to the control of diffuse sources of a broader spectrum of contaminants that impact human water use. In the developing countries of the inter-tropical zone, however, rapidly expanding populations, a growing industrial economy and extensive urbanization have only recently reached an intensity at which cultural eutrophication can no longer be ignored. Further, initial attempts at applying temperate zone control measures in this region have been largely unsuccessful. Modification of the temperate zone eutrophication paradigm will be needed, especially to address the differing climatic and hydrological conditions, if cultural eutrophication is to be contained in this region, where eutrophication-related diseases continue to be a primary cause of human distress.     

The Influence of Climatic Change on Price Fluctuations in Germany During the 16th Century Price Revolution

In our paper we analyze the influence of climatic changes on annual price fluctuations (harvest year) of agricultural products in Germany during the 16th century price revolution. The price series under analysis are from Nuremberg, Cologne, Augsburg, and Munich. The prices are compared with quarterly climatic indices for Germany, which cover the observation period 1500-1599. The main finding is that the length of the vegetation period is an important factor in determining grain price fluctuations. During the climatic deterioration in the 16th century, there is some evidence that the impact of climate (and therefore of supply fluctuations) on grain price fluctuations increases.     

Measurement of the Diurnal Variation of the OH Radical Concentration and Analysis of the Data by Modelling

Daily variations of the hydroxyl radical concentration have been measured during a campaign at the Weybourne Atmospheric Observatory (WAO) in June 1995. These measurements are compared with box model calculations, based on a slightly modified, second generation Regional Acid Deposition Model (RADM2). Results from eight days of the comparison are presented. A detailed analysis and discussion of the different source and sink terms is given for two days: Julian Day (JD) 170 (19 June, and 178 (27 June). In both cases excellent agreement between the measurements and the calculation is obtained, indicating that the model describes the OH chemistry sufficiently well. Furthermore, the analysis of these days demonstrate that JD 170 is dominated by the NOx catalysed OH production, whereas JD 178 is influenced by OH formation via ozone photolysis.     

Chicxulub impact ejecta from Albion Island, Belize

Impact ejecta from the Albion Formation are exposed in northern Belize. The ejecta come from the outer portion of the continuous ejecta blanket of the Chicxulub crater, which is located 360 km to the northwest. The basal unit of the Albion Formation is a 1-m-thick clay and dolomite spheroid bed composed of up to four discrete flows. The clay spheroids are altered impact glass, and the dolomite spheroids are accretionary lapilli. The upper unit is a 15-m-thick coarse diamictite bed containing altered glass, large accretionary blocks, striated, polished, and impacted cobbles, and rare shocked quartz. The abundance of accretionary clasts, evidence for atmospheric drag sorting, and the presence of multiple flows in the Albion Formation indicate that atmospheres play an important role in the formation of the outer portions of continuous ejecta blankets of large craters.     

Toward a sustainable estuary in north carolina's albemarle and pamlico sounds: Some implications for the Baltic Sea

A major task in developing a management strategy for the Baltic Sea will be the establishment of a program that adheres to the philosophy of sustainable use and is capable of implementation. For many nations this has proven to be a very difficult task marked with successes and failures. This paper discusses North Carolina's attempts to move toward sustainability in its Albemarle and Pamlico estuaries. The paper concludes with some lessons learned that could be helpful to the Baltic region as it strives for sustainability.     

Laboratory simulation of the physical processes occurring on and near the surfaces of comet nuclei

Abstract— Laboratory comet simulation experiments are discussed in the context of theoretical models and recent ground-based and spacecraft observations, especially the Giotto observations of P/Halley. The set-up of various comet simulation experiments is reviewed. A number of small-scale experiments have been performed in many laboratories since the early 1960s. However, the largest and most ambitious series of experiments were the comet simulation experiments known as KOSI (German = Kometen Simulation). These experiments were prompted by the appearance of Comet P/Halley in 1986 and in planning for the European Space Agency's Rossetta mission that was originally scheduled to return samples. They were performed between 1987 and 1993 using the German Space Agency's (DLR) space hardware testing facilities in Cologne. As with attempts to reproduce any natural phenomenon in the laboratory, there are deficiencies in such experiments while there are major new insights to be gained. Simulation experiments have enabled the development of methods for making comet analogues and for exploring the properties of such materials in detail. These experiments have provided new insights into the morphology and physical behavior of aggregates formed from silicate grains likely to exist in comets. Formation of a dust mantle on the surfaces and a system of ice layers below the mantle caused by chemical differentiation have been identified after the insolation of the artificial comet. The mechanisms for heat transfer between the comet's surface and its interior, the associated gas diffusion from the interior of the surface, and compositional, structural, and isotopic changes that occur near the surface have been described by modeling the experimental results. The mechanisms of the ejection of dust and ice grains from the surface and the importance of gas-drag in propelling grains have also been explored.     

Progressive development of lattice preferred orientations (LPOs) of naturally deformed quartz within a transpressional collision zone (Panafrican Orogen in the Eastern Desert of Egypt)

Lattice preferred orientations (LPOs) of quartz were used to establish differences in deformation geometry, finite strain, and temperature within a transpressional collision zone within the Panafrican Orogen in the Eastern Desert of Egypt. Metamorphic and/or magmatic core complexes in the area are bordered in the NW and SW by ductile sinistral NW-trending strike-slip zones and low angle normal faults (LANFs). Simultaneous activity of both fault systems suggests bulk W–E shortening coeval with orogen-parallel extension. Displacement partitioned into orogen-parallel sinistral strike-slip faults and LANFs. This study compares both quartz-LPOs in shear-zones and normal faults.From south to north, quartz c-axis data show a continuous evolution along orogen-parallel strike-slip faults from maxima in Y, with a slight tendency to oblique single girdles at the margins of the Wadi Beitan and Hafafit complexes, to asymmetric crossed girdles and oblique single girdles along the margins of the Sibai and Meatiq complexes. The NW-directed LANFs to the NW of the Hafafit and the SE-directed LANFs to the SE of the Sibai show maxima in Y. The SE-directed LANF at the SE margin of the Meatiq complex shows symmetric crossed girdles, indicating coaxial deformation geometry.Oblique single girdles and maxima in Y occur in the southern part of the orogen, whereas crossed girdle distributions dominate in the northern part. The variation in quartz c-axis patterns is explained in terms of decreasing metamorphic grade during deformation from the S (medium to high grade) to the N (low grade), and decreasing finite strain. This is in accordance with the general progression of transpressional tectonics and exhumation of core complexes from S to N.     

Chemical availability of arsenic and heavy metals in sediments from abandoned cinnabar mine tailings

The understanding of the solid-phase speciation of arsenic in soils and sediments is important in the evaluations of its potential mobility and availability in the environment. The spoil heaps of abandoned mercury mines contain waste materials with high arsenic and heavy metals concentrations. The weathering of these tailings can cause their mobilization to the surroundings. In this work, the mobility and availability of arsenic and some heavy metals were evaluated in sediments from two heavily polluted mercury mining districts in Asturias (NW Spain). For this purpose, a slightly modified version of the Bureau Community of Reference sequential extraction scheme was applied to sediments. The total contents in the operationally defined fractions were analysed by inductively coupled plasma-atomic emission spectrometry. Extremely high total arsenic concentrations were found in all sediments ranging from 4,000 to 24,800 mg kg^?1. High easily mobilizable arsenic contents were found in the first mining area, related to the solubilization of Ca-bearing phases, supported by extracts analyses, X-ray diffraction results and the positive correlation found among the As and Ca fractionations. Ni and Zn were the most mobile among heavy metals, being Cr the least mobile, suggesting an anthropogenic origin due to the metallurgical processes, transport or dispersion generated from neighbour spoil heaps. In the second mining area, the bulk of As was concentrated in the residual phase, as well as Cr, Cu, Fe, Pb, Ti, indicating a mineralogical origin and the low availability of these elements. The strong correlations established between As and Fe and Ti distributions support the hypothesis that As is mainly associated to structural mineral phases in these sediments.