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481.
H. Loßnitzer 《Theoretical and Applied Climatology》1958,9(1):73-79
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.
Mit 1 Textabbildung
Herrn Dr.Anders K. ?ngstr?m zu seinem 70. Geburtstag gewidmet. 相似文献
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.
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.
Mit 1 Textabbildung
Herrn Dr.Anders K. ?ngstr?m zu seinem 70. Geburtstag gewidmet. 相似文献
482.
Late-glacial ice advances in the western Italian Alps 总被引:1,自引:0,他引:1
STEPHEN c. PORTER GIUSEPPE OROMBELLI 《Boreas: An International Journal of Quaternary Research》1982,11(2):125-140
The extent of ice on the south side of the Mont Blanc massif during two late-glacial readvances is known primarily from the distribution of crystalline erratics on sedimentary and metasedimentary terrain, and from the distribution of end moraines and outwash remants. Similar dual moraine complexes are found elsewhere in upper Val d'Aosta and indicate that the pattern is regional in character. During the earlier readvance equilibrium-line altitudes were ca. 450 ± 50m lower than at present, whereas during the later readvance they were ca. 350 ± 50 m lower. The moraines, not yet closely dated, were deposited sometime after 14,200 14 C Years ago by which time Lago'd Alice near the margin of the würm moraine system at Ivrea had been deglaciated, and before 8400 years ago, at which time Rutor Glacier in upper Val d'Aosta was no larger than at present. The younger moraines are believed to correlate with Egesen moraines on the north side of the Alps, whereas the older set may either correlate with an early phase of the Egesen or with Daun advance. 相似文献
483.
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). 相似文献
484.
Josette Garnier Pierre Servais Gilles Billen Maïa Akopian Natacha Brion 《Estuaries and Coasts》2001,24(6):964-976
Ecological processes driving the oxygen budget were investigated in the downstream part of the Seine River and its estuary. Phytoplankton and bacterioplankton production were measured along longitudinal profiles (11 to 17 stations) in a range of low discharges from 300 m3 s−1 in 1993 and 1995 to 140 m3 s−1 in 1996. Values representative of the water column were based on investigations carried out during two tidal cycles. Net primary production was invariably greatest in the freshwater estuary, from Poses to Rouen (from 500 to 1,000 μg C l−1 d−1 between PK 202 and 240) and decreased sharply downstream (from 10 to 25 μg c l−1 d−1 between PK 250 and 310). This decrease was mainly due to the deterioration of the light conditions with the increase in depth and suspended matter concentrations. Heterotrophic activity was maximum in the reach where primary production declined. Judging by the production:respiration ratio (P:R), the system appeared clearly heterotrophic in the Seine River immediately downstream of the Paris region due to high allochthonous organic pollution by the incompletely treated Parisian effluents and in the part of the estuary characterized by intense degradation of autochthonous material. Because the effluents are not treated by a nitrification step, the oxygen consumption due to nitrification was much higher than expected from the P:R ratio. Oxidation of ammonium represented an oxygen consumption of between 1 and 14 g O2 m−2 d−1, almost equalling the sum of heterotrophic respirations that were barely balanced by photosynthesis. The reaeration flux at the water-atmosphere interface was deduced from the calculations and a reaeration coefficient was estimated. 相似文献
485.
Dreissena larval fluxes were studied in the lower stretch of the Seine River in 1996–1998. Fluxes reached 150×1012 ind d−1, representing a larval concentration of 5,000 ind l−1 in the Seine estuary. We showed that a sampling frequency with a 3-d interval allowed us to adequately estimate the annual production of larvae. The water residence time in the Seine River and estuary is sufficient for theDreissena larvae to complete their cycle and settlement. High abundance of the larvae in the plankton samples from the Seine River and its estuary showed the existence of a large community of benthic adults, known to be powerful filter-feeders. The progenitor population and the geographical extent of the adultDreissena were estimated from cohort analyses of the planktonic larvae. The maximum density ofDreissena was found in the highly channelized part of the estuary (up to 4,500 ind m−2). Estimated values were compared with concentration of mussels in the benthic traps and samples. Calculated filtration rates of benthic mussels were compared with those of larvae at different stages and with filtration of the zooplankton community. The impact of theDreissena was much higher than that of zooplankton; the filtration of the larvae exceeded that of adults during short periods of maximum larval emission. 相似文献
486.
In this paper we investigate the behaviour of Newton's kernel in the integration for topographical effects needed for solving the boundary value problem of geodesy. We follow the standard procedure and develop the kernel into a Taylor series in height and look at the convergence of this series when the integral is evaluated numerically on a geographical grid, as is always the case in practice. We show that the Taylor series converges very rapidly for the integration over the distant zone, i.e., the zone well removed from the point of interest. We also show that the series diverges in the vicinity of the point of interest when the grid becomes too dense. Generally, when the grid step is smaller than either the height of the point of interest, or the difference between its height and those of the neighbouring points. Thus we claim that the Taylor series version of Newton's kernel cannot be used for evaluating topographical effects on too dense a topographical mesh. 相似文献
487.
Chaotic radar signal processing over the sea 总被引:1,自引:0,他引:1
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 相似文献
488.
Jen-Men Lo 《Ocean Engineering》1991,18(5)
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. 相似文献
489.
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. 相似文献
490.
Impact of Brunswick River Mouth Training Walls on Adjacent Beaches, Brunswick Heads, New South Wales, Australia 总被引:1,自引:0,他引:1
1 .IntroductionTheBrunswickbeach barrierbegantodeveloparound 6 50 0yearsagoattheendofthepostglacialmarinetransgression .Onshoreandalongshoretransportofmarinesandsoccurredfollowingthestabi lizationofsealevelresultinginbeachandduneextensionwhichoccurredonmanyNSWbeachesuntilabout30 0 0to 1 0 0 0yearsBP (Roy ,1 980 ) ,followedbyperiodsofstabilitytorecession .TherecessionalongthenorthernNSWandsouthernQLDcoastisattributedtocontinuingnorthwardlongshoresandtransportestimatedatbetween 2 0 0 0 0 0m… 相似文献