On the local multiscale determination of the Earth’s disturbing potential from discrete deflections of the vertical

As a first approximation, the Earth is a sphere; as a second approximation, it may be considered an ellipsoid of revolution. The deviations of the actual Earth’s gravity field from the ellipsoidal “normal” field are so small that they can be understood to be linear. The splitting of the Earth’s gravity field into a “normal” and a remaining small “disturbing” field considerably simplifies the problem of its determination. Under the assumption of an ellipsoidal Earth model, high observational accuracy is achievable only if the deviation (deflection of the vertical) of the physical plumb line, to which measurements refer, from the ellipsoidal normal is not ignored. Hence, the determination of the disturbing potential from known deflections of the vertical is a central problem of physical geodesy. In this paper, we propose a new, well-promising method for modelling the disturbing potential locally from the deflections of the vertical. Essential tools are integral formulae on the sphere based on Green’s function with respect to the Beltrami operator. The determination of the disturbing potential from deflections of the vertical is formulated as a multiscale procedure involving scale-dependent regularized versions of the surface gradient of the Green function. The modelling process is based on a multiscale framework by use of locally supported surface curl-free vector wavelets.      

Radiation balance over low-lying and mountainous areas in south-west Germany

Summary  Surface radiative fluxes play a major role in the energy exchange process between the atmosphere and earth surface and are thus very crucial to climatic processes within the atmospheric boundary layer. Based on four years REKLIP (REgio-KLIma-Project) data set of measured radiative fluxes and additional supporting meteorological variables, the surface radiation regime for selected lowland site (Bremgarten 212 m a.s.l.) and mountain sites (Geiersnest at 870 m a.s.l.; Feldberg 1489 m a.s.l.) in the southern Upper Rhine valley region (south-west Germany) has been reported. Time series of radiative fluxes and surface albedo showed significant inter-site differences. Possible reasons for the observed differences have been made. Downward atmospheric radiation A _l at the study sites was parameterised in terms of air temperature, vapour pressure and cloud amount, all of which strongly govern the variation of A _l . Effective terrestrial radiation amounted to about 50% of absorbed shortwave radiation at the study sites annually. During clear sky conditions, global solar irradiance G _s constituted about 76.0% of the incident extraterrestrial solar irradiance at Feldberg mountain site but only 68.5% of that at Bremgarten lowland site. Annual cumulative of net radiative flux R _n amounted to 1722 MJm⁻² yr⁻¹ at the lowland site, while that at Geiersnest and Feldberg mountain sites constituted 84% and 73% respectively of the corresponding magnitude for the lowland site. In the same vein, annual mean of radiation efficiency (defined here as R _n /G _s ) amounted to 0.32 in Feldberg, 0.37 in Geiersnest and 0.41 in Bremgarten. Consequently the annual available energy, of which net radiative flux is representative, was smaller at the mountain ous sites relative to the lowland site during the study period. Inter-annual variability of net radiative flux, its constituent variables and derivatives at the study sites were generally below 10%, with longwave fluxes showing the lowest fluctuation. This renders the measured data quite suitable for modelling purposes. In winter, mean daily sums of R _n showed a slow rise with cloud amount N at the lowland site but a sharp rise with N at Feldberg mountain site. In summer however, mean daily sums of R _n declined significantly with N as well as Linke turbidity factor at the study sites. Received June 24, 1999 Revised November 2, 2000     

Conditions and formation mechanism of carbon phases in late quarternary geyzerites and travertines of Ol’khon area and Ol’khon Island (Baikal rift zone)

Late Quaternary geyserite and travertine in Ol’khon Area and Ol’khon Island contain a recently discovered high-temperature association of hydrocarbon and carbonaceous phases, including highly crystalline graphite, α-carbyne, and bitumen, which were produced at temperatures no lower than 400°C. A carbon modification α-carbyne, which was previously found only among experimental products, was first identified in geyserite from the Ol’khon area. Nanometer-sized morphostructures and crystallites were detected on the surface of highly crystalline graphite from the geyserite and travertine. No such structures and crystallites have ever been found on graphite of magmatic, metamorphic, metasomatic, or pneumatolytic origin. The newly formed nanometer-sized morphostructures and crystallites should be regarded as typomorphic features of carbonaceous phases in high-temperature hydrothermal rocks. Graphite was likely produced in the geyserite and travertine by low-pressure polycondenssation of hydrocarbons, at free growth in open space from oversaturated solutions and/or a gas phase.     

Über den Zusammenhang der interdiurnen Veränderlichkeit mit der Dispersion des Luftdruckes

Zusammenfassung Ausgehend von einer Häufigkeitsverteilung der stündlichen Luftdruckschwankungen in der Gaußschen Form wird eine Verteilung für die täglichen Druckänderungen abgeleitet und der Zusammenhang mit der Häufigkeitsverteilung des Luftdruckes hergestellt. Dabei wird die Abhängigkeit des Mittelwertes der Druckschwankungen vom Barometerstand von Bedeutung. Eine solche empirische Ermittlung wurde für Wien in erster Näherung durchgeführt. Auf Grund des erwähnten Zusammenhanges kann die interdiurne Veränderlichkeit durch die Dispersion der Luftdruckhäufigkeitsverteilung ausgedrückt werden, was wiederum den beobachteten Parallelismus zwischen den Linien gleicher Dispersion und gleicher interdiurner Veränderlichkeit wiedergibt. Der errechnete Wert für die interdiurne Veränderlichkeit des Luftdruckes von Wien wird mit dem beobachteten verglichen.

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Summary Starting from a distribution of the hourly variations of atmospheric pressure according to Gauß a distribution for the daily variations is deduced and a connexion with the distribution of pressure is effected. With regard to these considerations the dependence of the mean value of the variations of pressure on the height of the barometer is important. In first approximation a statement of this mean value was made for Vienna. In consequence of the above mentioned connexion the mean value of the daily variations of pressure can be expressed by the dispersion of the distribution of pressure. Thus the observed parallelism between the isolines of the dispersion and those of the interdiurnal variability becomes understandable. The calculated and the observed value of the interdiurnal variability of pressu e at Vienna are compared with one another.

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Résumé Partant d'une distribution des fréquences des variations horaires de la pression atmosphérique selon la loi de Gauss, l'auteur en déduit une distribution des variations interdiurnes comparées à la distribution des fréquences de la pression elle-même. La valeur moyenne des variations de pression dépend de la hauteur barométrique. Vienne fait l'objet d'une telle recherche empirique en première approximation. Se fondant sur la relation mentionnée, on peut exprimer la variabilité interdiurne par la dispersion de la distribution des fréquences de la pression, ce qui met de nouveau en évidence le parallélisme observé entre les isolignes de la dispersion et celles de la variation interdiurne. On compare la valuer calculée de la variabilité interdiurne pour Vienne avec les valeurs observées.

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Mit 2 Textabbildungen.     

江西永丰县梁坊橋变形礫岩

江西永豐縣南,古縣至瑤田間之梁坊橋附近,有一變形礫岩層,恰位於走向北10度東及北80度东兩逆斷層啣接處。該礫岩層中之礫石,多為扁平橢圓形,其長軸兩端逐漸尖化,外附絲澤、臘狀、光滑表皮,並有新生之雲母片及長纖維狀物質,於此光滑面上,常具深刻水平擦痕。這些變形礫石,受外力變形後,共長軸近於東西,扁平面平行於北80度東之斷層面舆附近岩層之片理。垂直變形礫石a,b,c三軸及膠結物質延長方向,分製薄片,在顯微鏡下觀察,其膠結物為灰白色雲母及許多無光性之黑色物質,呈顯著之流紋構造,內含大小不一之眼球狀石英粒等;石英礫石內之石英晶體,均具極强之波浪消光,於晶體四周,圍繞密擠再結晶之小型石英粒,而示標準磨碎構造。晶體本身含有無數極小之氣孔或包體,並作一定方向排列,而成變形紋理,平行於扭應面;在石英岩礫石內,石英粒均沿一定方向延長,並按其大小作帶狀排列。礫石內部,擁有極複雜之節理舆顯明之断層,這些事實象微着强烈的外力作用。根據弗氏旋轉台再結晶石英粒。軸及雲母底面等之統計舆分析,得知其晶體排列恆受扭應力支配。     

Geomorphology,acoustic backscatter,and processes in Santa Monica Bay from multibeam mapping

Santa Monica Bay was mapped in 1996 using a high-resolution multibeam system, providing the first substantial update of the submarine geomorphology since the initial compilation by Shepard and Emery [(1941) Geol. Soc. Amer. Spec. Paper 31]. The multibeam mapping generated not only high-resolution bathymetry, but also coregistered, calibrated acoustic backscatter at 95 kHz. The geomorphology has been subdivided into six provinces; shelf, marginal plateau, submarine canyon, basin slope, apron, and basin. The dimensions, gradients, and backscatter characteristics of each province is described and related to a combination of tectonics, climate, sea level, and sediment supply. Fluctuations of eustatic sea level have had a profound effect on the area; by periodically eroding the surface of Santa Monica plateau, extending the mouth of the Los Angeles River to various locations along the shelf break, and by connecting submarine canyons to rivers. A wetter glacial climate undoubtedly generated more sediment to the rivers that then transported the increased sediment load to the low-stand coastline and canyon heads. The trends of Santa Monica Canyon and several bathymetric highs suggest a complex tectonic stress field that has controlled the various segments. There is no geomorphic evidence to suggest Redondo Canyon is fault controlled. The San Pedro fault can be extended more than 30 km to the northwest by the alignment of a series of bathymetric highs and abrupt changes in direction of channel thalwegs.     

Enhanced Acoustic Backscatter Due to High Abundance of Sand Dollars, Dendraster excentricus

Detailed acoustic surveys of benthic sediments were conducted in July 1995 and September 1998 in the vicinity of Humboldt Bay, California. During these surveys, a band of enhanced acoustic backscatter was observed offshore from the bay entrance, approximately parallel to the isobaths, in water depths ranging from 16-24 m. In order to assess the cause of the increase in backscatter levels, a more comprehensive study was conducted in August and September 1999 using 100 kHz side-scan sonar, bottom grab sampling and underwater video recording. New observations indicated that a dense population of sand dollars ( Dendraster excentricus ) coincided with the enhanced backscatter band. Compared to the two previous acoustic studies, the central section of the band expanded westward by 180 m and the southern section of the band shifted eastward by 160 m, possibly resulting from a change in the biological or physical factors which influence the location and breadth of sand dollars. The relationship between high sand dollar abundance and enhanced acoustic backscatter was further verified in the nearshore region off Samoa Beach California, where a dense, banded population of sand dollars was previously observed. Video footage confirmed the presence of a band of sand dollars, also nominally parallel to the isobaths, in water depths of 8-15 m. A band of enhanced backscatter coincided with the dense sand dollar population. The identification of dense aggregations of sand dollars through enhanced acoustic backscatter could lead to the use of acoustic techniques to study sand dollar distributions and abundance.