The fog front of 25 May 1989 — A gravity flow?

Summary During the field experiment FRONTEX 1989 a shallow cold front with a fog field behind its leading edge was observed over the North Sea. The fog field was about 70 km wide, 160 m deep at the front side and 400 m deep at the rear side and was capped by a strong frontal inversion. With increasing height of the inversion the fog broke up into cumulus clouds. The horizontal temperature gradient was largest at 500 m with 9 K/100 km. The observed segment of the front was situated near the col of a geostrophic deformation field with vanishing cross-front wind but non-vanishing cross-front confluence. The front moved at a rate of 5 m/s. It exhibits characteristics of a gravity current which propagates into a stably stratified environment.The physical processes leading to the observed frontal structure and motion are elucidated by experiments with a two-dimensional numerical model. The charateristics of the observed front can be reproduced if both, geostrophic forcing and boundary-layer processes, such as air-sea temperature difference, moisture content and cloud radiational cooling are taken into account. The development of the front under altered conditions is studied by the comparison of different simulations. The reason for the movement of the front is discussed refering to the mechanisms of geostrophic forcing and the forcing by surface friction. The analysis of the forces acting on the cold air mass shows that the Coriolis force is important at some distance behind the frontal head, but has little effect on the processes at the frontal head.With 13 Figures     

Das erdmagnetische Feld im Jahr 1992 nach Messungen des Erdmagnetischen Observatoriums Wingst

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Untersuchungen über die Struktur des Centroplasmas und die Drehrichtung einigerOscillatoriaarten

Zusammenfassung An vier verschiedenen Arten der GattungOscillatoria konnte nach Anf?rbung mit Acridinorange im Fluoreszenzmikroskop die Feinstruktur des Centroplasmas beobachtet werden. Besonders deutlich liessenO. animalis undO. terebriformis feine L?ngsstrukturen erkennen, die schr?g zur Trichomachse ausgerichtet waren und auf einen spiraligen Bau des gesamten Protoplasten schliessen liessen. Voraussetzung für diese Versuche waren junge Algen aus 3–4 Tage alten Kulturen. Die Anordnung der nukleins?urehaltigen Strukturen in den Zellen stimmte mit der Drehrichtung der lebenden Algen überein. Es wird angenommen, dass die Windungsrichtung der Oscillatorien artspezifisch ist.

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Summary It was possible, after staining with acridin orange, to observe in the fluoromicroscope the fine structure of the centroplasm of four different species of the genusOscillatoria. Especially in the case ofO. animalis andO. terebriformis, fine longitudinal structures could be distinguished; they run obliquely towards the trichome axis and could be a sign of spiral structure of the whole protoplast. Such structures can be observed only on young algae taken from cultures 3 or 4 days old. The arrangement of the nucleinate structures in the cells corresponds to the twisting movement of the live algae. It can be supposed that the twisting direction taken by the Oscillatoria is characteristic of the species.

     

Sudoit („dioktaedrischer Chlorit“, „Al-Chlorit“) im Cornberger Sandstein von Cornberg/Hessen

Sudoite, muscovite, and quartz are authigenic minerals of the Cornberger Sandstein, the youngest eolian member of the uppermost Lower Permian. The sudoite is to a great extent similar to the material from the Kesselberg area (Black Forest, Germany).

$$\begin{gathered} n_z \approx n_z = 1.572 \pm 0.002 \hfill \\ \underline {{\text{ }}n_x = 1.568 \pm 0.003} \hfill \\ {\text{ }}\Theta \Delta = 0.004 \pm 0.003 \hfill \\ \end{gathered} $$     

Tektonik der Siegener Schichten im mittleren Wiedtal (Westerwald)

Zusammenfassung Feintektonische Untersuchungen, ergänzt durch stratigraphische Profilaufnahme, erbrachten den Nachweis eines Hönningen-Seifener-Sattels aus Schichten des Unteren Siegen, Im NW wie SE wird dieser Sattel von flachwelligen Muldenzonen begleitet, deren südöstliche in Richtung auf die Siegerländer Hauptüberschiebung einen zunehmenden Schuppenbau zeigt.     

On the height scale of magnetic fields above sunspots derived from RATAN-600 observations

Model calculations of the S-component are compared with observations of the RATAN-600 telescope at five discrete microwave frequencies referring to active region McMath No. 15974 on May 1, 1979. The spectral variations of source diameter, flux density, and degree of polarization are used to derive the height scale of the magnetic field in accordance with a magnetic dipole distribution under the assumption of advanced temperature and electron density distributions according to most recent EUV observations.     

Neuordnung der Schriftleitung

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