Large are variability in climate-based soil moisture estimates and implications for remote sensing

Although the basic physical relationships between various remotely sensed signatures and soil are sound, the representativeness of pixel-averaged wetness used to interpret the remotely sensed data is often suspect and at times even doubtful. To study the affect of local variation in soil moisture on the large-area average, mean areal precipitation, temperature and modelled soil moisture in 1/4° grid cells were analyzed for a 700 km by 400 km region in the US Southern Great Plains. Variability in five years of mean daily grid cell data was investigated for 150 km² study sites, approximately corresponding in size to a satellite microwave pixel. The number of wetted grid cells and the magnitude of precipitation in grid cells within a site were highly variable. The variability of each of these factors is critical, and will not only influence mean site wetness, but also how the area will be seen from space. Analysis indicated that similar mean site precipitation values may result from numerous widely differing combinations of precipitation magnitude and watted gric cell population. Consequently, mean site moisture is also highly variable in the distribution and magnitude of the individual cell moisture values. Extreme values in several grid cells may severely bias the quadrant mean, while influencing a remote measurement much less. Although large-scale surface wetness may eventually be reliably inferred from satellite measurements, a degree of uncertainty will always exist, especially in semi-arid areas. One may be required to associate mean soil moisture with an expected distribution of wetness within a pixel.     

The Influence of NaBr/NaCl Ratio on the Br--Catalysed Production of Halogenated Radicals

The activation of Br^- and Cl^- to atomic Br and Cl in sea-spray aerosol was investigated in smog-chamber experiments. In the presence of O₃, hydrocarbons and NaCl aerosol alone no activation was observed. By adding Br^- to the aerosol, the chain reaction: Br + O₃ BrO, BrO + HO₂ HOBr, HOBr HOBr(aq), HOBr(aq) + H⁺ + Br^- Br₂ (6), HOBr(aq) + H⁺ + Cl^- BrCl (7) was verified. The step from reaction (6) to (7) is accompanied by a decrease of the Br^-/Cl^- ratio from 1/600 to less than 1/2000. In the absence of sulphate, the chain is initiated by the reaction of OH(aq) with Br^-. The pH value decreases to less than 2 during the first minutes of the experiment and later on to almost 1 (in the absence of NO_x or SO₂). This is caused by the formation of oxalic acid from alkanes and toluene. In stopped flow experiments, the reduction of Br₂ by oxalic acid was observed to occur through a two-step mechanism: HC₂O₄ ^- + Br₂ Br^- + BrC₂O₄H (k₂₂, k_-22), BrC₂O₄H Br^- + H⁺ + 2 CO₂ (23) with the following rate constants and ratios of rate constants, k ± 2: k₂₂k_-23 / k_-22 = (2.9 ± 0.3) · 10^-4 s^-1, k_-22 / k_-23 = 7000 ± ₃₀₀₀ ¹³⁰⁰⁰ M^-1, k₂₂ = 2 ±_-1 ⁴ M^-1 s^-1, and k_-23 > 0.1 s^-1, k_-22 > 600 M^-1 s^-1. Oxalic acid may be responsible for the inhibition of the chain reaction observed at the end of the experiments.     

Untersuchungen an fränkischen Verwerfungen

Zusammenfassung An vier feldgeologisch untersuchten Beispielen, dem Gräfenthaler Horst im Frankenwald, der Fränkischen Linie bei Kronach, der Kulmbacher Verwerfung bei Kirchleus und an Verwerfungszonen im Steigerwald wird gezeigt, daß die fränkischen Verwerfungen als Flächen eines zusammenhängenden Strukturfeldes angesehen werden können, das trotz seiner verschiedenartigen Erscheinungsformen im Grund- und Deckgebirge auf eine gemeinsame Ursache zurückgehen dürfte.

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Four areas in Northern Bavaria, the Gräfenthaler Horst in the Frankenwald, the Franconian Line near Kronach, the Kulmbach Fault near Kirchleus and fault zones in the Steigerwald, were investigated by different field methods. The authors are in the opinion that these Franconian faults are elements of a connecting structural region though different tectonic phenomena may be observed on the surface.

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Résumé Dans le nord de la Bavière des grands accidents tectoniques de direction NW/ SE, dont quelques-uns traversent le socle hercynien, d'autres la couverture mésozoique avoisinante, ont été étudiés par des methodes diverses. Quoique leurs caractères changent selon l'étage affectée, ces accidents sont des élements d'un seul domaine structural et ont apparement une origine commune.

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Herrn Professor Dr.Roland Brinkmann zum 70. Geburtstag gewidmet.     

Mineralbestand und Gefügebilder in Faseraggregaten von kohliger Substanz („Thucholith“) aus den Witwatersrand-Konglomeraten

Zusammenfassung Es werden die typischen Faseraggregate von kohliger Substanz beschrieben, die oft an den Liegendkontakten wirtschaftlich wichtiger Gold-Uran-Konglomerate des südafrikanischen Witwatersrand-Systems in dünnen Lagen auftreten. Der Mineralbestand dieser Aggregate wird erzmikroskopisch untersucht, wobei Gold und Uranpecherz besonders berücksichtigt werden. Die Faserung wird als Wachstum senkrecht zur Wandung schichtparalleler Ablösungsklüfte erklärt (parallelstengelige Kluftfüllung im Sinne vonMügge, 1928).An primären detritischen Mineralien finden sich in diesen Aggregaten Pyrit, Kobaltglanz, Chromit, Zirkon und Iridosmium; umgelagerte authigene Bestandteile der Schwerefraktion sind im wesentlichen Gold, Linneit, Kupferkies, Bleiglanz. Zinkblende und Spuren von Magnetkies. Der primär ebenfalls detritische Uranpecherzanteil liegt ausschließlich in stark resorbierter Form vor, d. h. die UO₂-Partikel lösen sich in den verfestigten Kohlenwasserstoffen zu einzelnen Bruchstücken auf, die dann allmählich adsorptiv verdaut werden.Auffallend sind die charakteristischen Fließgefüge der kohligen Substanz um die allogenen Bestandteile der Paragenese, insbesondere um den mengenmäßig vorherrschenden Pyrit. Es kommt zu typischen Augenbildungen, wobei sich häufig Gold, Bleiglanz oder sekundärer Quarz in den Druckschattenräumen an beiden Enden der Streckungshöfe absetzen. Ähnliche Fließgefüge lassen sich auch um einige frühe Neubildungen wie Zinkblende beobachten.Es ergibt sich somit aus den Untersuchungen, daß die kohlige Substanz in ihrer heutigen Form jünger ist als die primären detritischen Mineralien, daß aber andererseits die pseudohydrothermale Umlagerung der Hauptmasse des Goldes (das ursprünglich ebenfalls in detritischer Form vorgelegen haben muß) teilweise noch später erfolgt ist. Dasselbe gilt für einige genetisch junge Sulfide wie Linneit, z. T. auch für Kupferkies.

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The footwall of the principal uraniferous congiomerates occurring within the Witwatersrand System (South Africa) is often characterized by a fibrous carbon or thucholite seam, ranging in thickness from parts of a mm to several cm (Figs. 1 and 2). The carbonaceous material has formed by radiolytic polymerization of originally mobile (preferably gaseous) hydrocarbons percolating through the strata, the prerequisite for its formation thus being the presence of detrital uraninite within the heavy fraction of the individual reefs. The conspicuous columnar fabric of the aggregates is explained as being due to growth at right angles to the bedding planes comparable with several other fibrous minerals (Mügge, 1928).The association between heavy minerals and carbonaceous matter must be particularly intimate, since the latter has accumulated in the lowermost footwall portions where the bulk of the heavy suite of the conglomerates is concentrated. Primary detrital constituents within the fibrous aggregates are pyrite, cobaltite, chromite, zircon, and iridosmine (Figs. 4 and 5); authigenic recrystallized heavy minerals are gold, linnaeite, chalcopyrite, galena, sphalerite, as well as traces of pyrrhotite (Figs. 3 and 6). The detrital uraninite fraction is to a large extent replaced by carbonaceous matter, i. e. the UO₂-particles are in the state of floating apart in, and being gradually digested by, the solid hydrocarbons (Fig. 8). Very often the carbonaceous matter displays a prominent flow lamination around the allogenic constituents, especially around the ubiquitous pyrite (Fig. 4). Rise is given thereby to a typical augen structure; gold, galena or secondary quartz are commonly deposited in the pressure-shadows on either side of the inclusions. Similar fabrics may be observed around some early-formed authigenic minerals like sphalerite (Fig. 6); the latter mostly appears to be dragged apart (boudinagedrd) and carbon usually comes to occupy the interstices between the individual fragments. Elongated fragments often tend to arrange themselves parallel to the flow laminae.It is evident from the investigation that carbonaceous matter is distinctly younger than the primary detrital minerals. On the other hand, it is likewise obvious that the pseudohydrothermal recrystallization of the main mass of the gold (which originally also formed part of the heavy suite) must have taken place at a still later stage. The same applies to several genetically young Sulfides as linnaeite, in part also to chalcopyrite.

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Erweiterte Fassung eines Vortrages, den der Verfasser am 5. 9. 65 auf der 43. Jahrestagung der Deutschen Mineralogischen Gesellschaft in Hannover gehalten hat.     

Carbon dioxide fluxes of soils and mosses in wet tundra of Taimyr Peninsula, Siberia: controlling factors and contribution to net system fluxes

Knowledge of the environmental controls of carbon dioxide fluxes is essential for understanding the dynamics of carbon exchange between ecosystems and atmosphere. In this study we investigated soil respiration and moss photosynthesis as well as their contribution to the net carbon dioxide flux of two different wet tundra systems. During two summers, in situ carbon dioxide fluxes were measured in a tussock tundra and in a low-centre polygonal tundra on Taimyr Peninsula, central Siberia. Measurements were carried out by means of a multichannel gas exchange system. Results show pronounced differences in soil respiration rates as related to microscale topography, mainly due to differences of soil water table and soil temperatures. Modelling of soil respiration for individual microsites revealed differences of process performance with respect to both factors. The wet microsites showed the highest potential regarding an increase of soil respiration rates in warmer and drier climate change scenarios. Another important process compensating the CO₂ release from the soil was the photosynthesis of the moss layer, assimilating as much as 51% to 98% of the daily amount of carbon dioxide released from wet tundra soils. This result demonstrates the importance of mosses in the context of tundra ecosystem processes. The magnitude of net system fluxes of the whole system at the depression of the polygonal tundra was strongly influenced by changes in soil water table. Consequently, any changes of the hydrology, as anticipated in the context of global change, would effectively alter the carbon balance of wet tundra systems.     

Wavelet transform-based seismic facies classification and modelling: application to a geothermal target horizon in the NE German Basin

At the geothermal test site near Groß Schönebeck (NE German Basin), a new 3D seismic reflection survey was conducted to study geothermal target layers at around 4 km depth and 150°C. We present a workflow for seismic facies classification and modelling which is applied to a prospective sandstone horizon within the Rotliegend formation. Signal attributes are calculated along the horizon using the continuous Morlet wavelet transform. We use a short mother wavelet to allow for the temporal resolution of the relatively short reflection signals to be analysed. Time-frequency domain data patterns form the input of a neural network clustering using self-organizing maps. Neural model patterns are adopted during iterative learning to simulate the information inherent in the input data. After training we determine a gradient function across the self-organizing maps and apply an image processing technique called watershed segmentation. The result is a pattern clustering based on similarities in wavelet transform characteristics. Three different types of wavelet transform patterns were found for the sandstone horizon. We apply seismic waveform modelling to improve the understanding of the classification results. The modelling tests indicate that thickness variations have a much stronger influence on the wavelet transform response of the sandstone horizon compared with reasonable variations of seismic attenuation. In our interpretation, the assumed thickness variations could be a result of variable paleo-topography during deposition of predominantly fluvial sediments. A distinct seismic facies distribution is interpreted as a system of thicker paleo-channels deposited within a deepened landscape. The results provide constraints for the ongoing development of the geothermal test site.     

EUREC<Superscript>4</Superscript>A: A Field Campaign to Elucidate the Couplings Between Clouds,Convection and Circulation

Trade-wind cumuli constitute the cloud type with the highest frequency of occurrence on Earth, and it has been shown that their sensitivity to changing environmental conditions will critically influence the magnitude and pace of future global warming. Research over the last decade has pointed out the importance of the interplay between clouds, convection and circulation in controling this sensitivity. Numerical models represent this interplay in diverse ways, which translates into different responses of trade-cumuli to climate perturbations. Climate models predict that the area covered by shallow cumuli at cloud base is very sensitive to changes in environmental conditions, while process models suggest the opposite. To understand and resolve this contradiction, we propose to organize a field campaign aimed at quantifying the physical properties of trade-cumuli (e.g., cloud fraction and water content) as a function of the large-scale environment. Beyond a better understanding of clouds-circulation coupling processes, the campaign will provide a reference data set that may be used as a benchmark for advancing the modelling and the satellite remote sensing of clouds and circulation. It will also be an opportunity for complementary investigations such as evaluating model convective parameterizations or studying the role of ocean mesoscale eddies in air–sea interactions and convective organization.