The role of the NNW structural trend in the recent geodynamic evolution of north-eastern sicily and its volcanic implications in the etnean area

The seismic and eruptive events occurring in Eastern Sicily between 1978 and 1981 are analyzed with reference to the existence neoctectonic structures beginning with the Gulf of Patti earthquake (1978, Lower Tyrrhenian Basin). From this analysis, the geodynamic consistency of the movements developing along the NNW and NE trends becomes apparent. In particular, the relation between these two trends enables the authors to verify their previously elaborated deformation model for the Etnean area and to emphasize its coherence with the regional geodynamic context. Finally, the close connection is shown between the Etnean area and the NNW-SSE wrench zone breaking the Southern Calabro-Peloritan Arc.     

Microtremors and volcanic explosions at Stromboli (Aeolian Islands)

Seismic observations were carried out at Stromboli from October 16^th to 24^th, 1972. One three-component seismic station was set up at Semaforo Nuovo, about 2 km on the E of the crater plain. Seismic observations showed the occurrence of microtremors, with variable amplitude but constant frequency content, and different types of explosion earthquakes. Spectral and vibration orbit analyses of microtremors and quakes were made in order to infer their nature and the depth of origin. Changes in microtremor amplitudes corresponding to different phases of volcanic activity indicate that their study may be useful in forecasting strongly explosive volcanic phases at Stromboli.     

Ergebnisse von Interferenzfiltermessungen der Sonnenstrahlung von 350 bis 1000 nm

Zusammenfassung Es werden aktinometrische Messungen der Sonnenstrahlung mit Interferenzfiltern, die am Observatorium Freiburg i. Br. gewonnen wurden, einer kritischen Betrachtung unterzogen. Die Me?werteverifizieren an sich bekannte Tatsachen über das Verhalten der Sonnenstrahlung in ihren einzelnen Spektralbereichen gegenüber ?nderungen der Sonnenh?he, der atmosph?rischen Trübung und der H?henlage des Beobachtungsortes. Die leistungsf?higkeit und Empfindlichkeit der Me?methodik wird an Beispielen dargestellt. Für das anzustrebende Ziel, aus Interferenzfiltermessungen die ?ngstr?mschen Trübungsparameter für einzelne ann?hernd monochromatische Spektralgebiete zu gewinnen, erscheinen die technischen Voraussetzungen zwar noch nicht ausreichend, aber erreichbar.

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Summary The author presents a critical study of actinometric measurements of the solar radiation with interference filters, carried out at the Freiburg/Br. Observatory. The measured values verify well-known facts on the reaction of the solar radiation in its different spectral regionsto variations of the sun's elevation, the atmospheric turbidity and the altitude of the place of observation. The efficiency and the sensibility of the measuring method are discussed. The technical assumptions for the aim of obtaining the ?ngstr?m turbidity parameters for some nearly monochromatic spectral regions from measurements with interference filters seem to be, if not yet sufficient, though attainable.

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Résumé L'auteur discute la méthode de mesures actinométriques du rayonnement solaire au moyen de filtres à interférences exécutées à l'Observatoire de Fribourg en Br. Ces mesures confirment les faits connus concernant le comportement des radiations solaires des diverses parties spectrales en fonction de la hauteur du soleil, du trouble atmosphérique et de l'altitude du lieu d'observation. Exemples du rendement et de la sensibilité de la méthode. S'il s'agit de déterminer les paramètres de trouble de ?ngstr?m pour certaines régions spectrales à peu près monochromatiques au moyen de filtres à interférences, on constate que les exigences techniques ne sont pas encore satisfaites, mais qu'elles pourront le devenir.

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Herrn Dr.Anders K. ?ngstr?m zu seinem 70. Geburtstag gewidmet.     

Contribution de l'étude exoscopique des quartz à la reconstitution paléogéographique des derniers épisodes du Quaternaire littoral du Congo

The paleogeographic and particularly palaeoclimatic evolution in the Congo at the end of the Quaternary has been investigated thoroughly with a study of grain surfaces using the scanning electron microscope. The succession of distinct physicochemical environment marks is characterized with the help of other methods (radiocarbon, micropaleontology). During a still-existing tropical climate, arid periods are contemporaneous with regressive phases (eolian, fluviatile, or pedogenetic reliefs of the grains) and humid periods correspond to transgressive phases (infratidal, intertidal, deltaic, lagoonal marks).     

Chaotic radar signal processing over the sea

It is demonstrated that the random nature of sea clutter may be explained as a chaotic phenomenon. For different sets of real sea clutter data, a correlation dimension analysis is used to show that sea clutter can be embedded in a finite-dimensional space. The result of correlation dimension analysis is used to construct a neural network predictor for reconstructing the dynamics of sea clutter. The deterministic model so obtained is shown to be capable of predicting the evolution of sea clutter. The predictive analysis is also used to analyze the dimension of sea clutter. Using the neural network as an approximation of the underlying dynamics of sea clutter, a dynamic-based detection technique is introduced and applied to the problem of detecting growlers (small fragments of icebergs) in sea clutter. The performance of this method is shown to be superior to that of a conventional detector for the real data sets used here     

A numerical model for combined refraction-diffraction of short waves on an island

A combined wave refraction-diffraction numerical model was developed to predict wave conditions around an arbitrary island. The methodology was based on the mild-slope equation, solved using a finite difference scheme with a marching procedure. The new model reduced the computer's memory demand considerably in comparison with finite-element, parabolic, error vector propagation and other finite difference approaches, and could therefore predict wave conditions for a large coastal area under given offshore boundary-wave conditions. Laboratory data on wave conditions under submerged circular and elliptical shoal conditions were selected to validate the numerical results. Good agreement was observed in all cases. Wave characteristics around an island were predicted using this model with the given deep-water wave condition. The model can predict wave conditions for any island with a mild-slope coastline.     

Surface-penetrating flexible membrane wave barriers of finite draft

The performance of surface-penetrating flexible membrane wave barriers of finite draft is studied. The interactions of a single membrane and dual membrane systems are examined with various system parameters. The analytical solutions are derived using eigenfunction expansions assuming linear wave theory and small membrane response. Wave transmission is determined for various combinations of membrane draft, protrusion above the water surface, membrane tension and membrane spacing. The numerical solutions are compared with data obtained from experiments conducted. Comparisons of transmission coefficient and energy loss show good agreement with suitably chosen parameters of viscous losses.     

Climate simulations for 1880–2003 with GISS modelE

We carry out climate simulations for 1880–2003 with GISS modelE driven by ten measured or estimated climate forcings. An ensemble of climate model runs is carried out for each forcing acting individually and for all forcing mechanisms acting together. We compare side-by-side simulated climate change for each forcing, all forcings, observations, unforced variability among model ensemble members, and, if available, observed variability. Discrepancies between observations and simulations with all forcings are due to model deficiencies, inaccurate or incomplete forcings, and imperfect observations. Although there are notable discrepancies between model and observations, the fidelity is sufficient to encourage use of the model for simulations of future climate change. By using a fixed well-documented model and accurately defining the 1880–2003 forcings, we aim to provide a benchmark against which the effect of improvements in the model, climate forcings, and observations can be tested. Principal model deficiencies include unrealistically weak tropical El Nino-like variability and a poor distribution of sea ice, with too much sea ice in the Northern Hemisphere and too little in the Southern Hemisphere. Greatest uncertainties in the forcings are the temporal and spatial variations of anthropogenic aerosols and their indirect effects on clouds. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

On the determination of boundary-layer parameters using velocity profile as the sole information

This paper proposes a numerical technique based on the least-square error method for evaluating fluxes and other surface-layer parameters. The special feature of this method is that it requires no a-priori knowledge of either the temperature profile or the roughness length z ₀. The accuracy of the method has been tested on both the Kansas and the Wangara experimental data. Results obtained compared favourably with those from direct measurements as well as from other studies using conventional approaches.