The Krakatoa Air-Sea Waves: an Example of Pulse Propagation in Coupled Systems   总被引：2，自引：0，他引：2  

David Harkrider  Frank Press 《Geophysical Journal International》1967,13(1-3):149-159

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SPECTRAL CHARACTERISTICS OF SURFACE-LAYER TURBULENCE OVER THE SUBURBS OF TIANJIN   总被引：1，自引：0，他引：1       下载免费PDF全文

(王存忠)  (曹文俊) 《Acta Meteorologica Sinica》1994,(2)

The paper computed the spectra of velocity and temperature,and the cospectra of velocity and temperature by theobservational data of July,1990 in the suburbs of Tianjin.The results show that the characteristics of the atmosphericturbulence spectra over the suburbs are basically in accordance with some typical results over the flat terrain.But thescale,on which turbulence can satisfy the isotropic condition,over the suburbs is larger than over the flat terrain.Thespectrum peak frequency range is a bit narrower.The feature of the spectrum range in low frequency(LF)is out ofaccordance with that of the flat terrain either.  相似文献   

Velocity structure and properties of the lunar crust     

M. N. Toksőz  F. Press  K. Anderson  A. Dainty  G. Latham  M. Ewing  J. Dorman  D. Lammlein  Y. Nakamura  G. Sutton  F. Duennebier 《Earth, Moon, and Planets》1972,4(3-4):490-504

Lunar seismic data from three Apollo seismometers are interpreted to determine the structure of the Moon's interior to a depth of about 100 km. The travel times and amplitudes ofP arrivals from Saturn IV B and LM impacts are interpreted in terms of a compressional velocity profile. The most outstanding feature of the model is that, in the Fra Mauro region of Oceanus Procellarum, the Moon has a 65 km thick layered crust. Other features of the model are: (i) rapid increase of velocity near the surface due to pressure effects on dry rocks, (ii) a discontinuity at a depth of about 25 km, (iii) near constant velocity (6.8 km/s) between 25 and 65 km deep, (iv) a major discontinuity at 65 km marking the base of the lunar crust, and (v) very high velocity (about 9 km/s) in the lunar mantle below the crust. Velocities in the upper layer of the crust match those of lunar basalts while those in the lower layer fall in the range of terrestrial gabbroic and anorthositic rocks.Lamant-Doherty Geological Observatory Contribution No. 1768.  相似文献   

Detrital spinels from alpinotype source rocks in middle Devonian sediments of the Rhenish Massif     

Dr. Susanne Press 《International Journal of Earth Sciences》1986,75(2):333-340

Middle Devonian sandy siltstones of the Gummersbach area (Rhenish Massif) show increased Cr contents (up to 675 ppm). The chromium is mainly associated with detrital Cr-Al spinels. The spinels are characterized by a wide spectrum of chemical composition.In more than 50% of 134 analyzed spinel grains the Cr₂O₃ content exceeds 50 wt %. The A1₂O₃ content which is negatively correlated to Cr₂O₃ reaches 40 wt %. The MgO contents are, with few exceptions, lower than the FeO contents; both elements are negatively correlated. The Fe₂O₃ contents which were calculated from a quarter of the grains rarely exceed 5 wt %. Besides Cr, Al, Fe, Mg TiO₂ contents were determined.The chemical composition of the detrital spinels indicates provenance from peridotites of an ophiolite suite.Provenance analysis shows that the source area of the Middle Devonian clastic sediments was situated in the north.

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Zusammenfassung In sandigen Siltsteinen des Mitteldevons des Bergischen Landes (Rheinisches Schiefergebirge) wurden erhöhte Cr-Gehalte von maximal 675 ppm festgestellt. Das Chrom ist überwiegend an detritische Spinelle gebunden. Mikrosondenuntersuchungen erbrachten eine große Variationsbreite im Chemismus dieser Spinelle. Über die Hälfte der 134 analysierten Körner weist mehr als 50 Gew % Cr₂O₃ auf. Der Al₂O₃-Gehalt, umgekehrt proportional zum Cr₂O₃-Gehalt, erreicht 40 Gew %. Die MgO-Gehalte sind bis auf wenige Ausnahmen kleiner als die FeO-Gehalte; beide Elemente sind negativ korreliert. Die Fe₂O₃-Gehalte, die von einem Viertel der Körner berechnet wurden, liegen meist unter 5 Gew %. Neben Cr, Al, Fe, Mg treten in einigen Spinellen meßbare TiO₂-Gehalte auf. Von ihrem Chemismus her lassen sich die detritischen Cr-Al-Spinelle von Peridotiten alpinotyper Ophiolite ableiten. Sedimentologische Befunde zeigen an, daß das Liefergebiet der klastischen mitteldevonischen Sedimente im Norden des Rheinischen Schiefergebirges gelegen hat.

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Résumé Les siltites sableuses du Dévonien moyen de la région de Gummersbach (Massif Schisteux Rhénan) montrent des teneurs en Cr élevées, jusqu'à un maximum de 675 ppm. Le chrome est lié principalement à des spinelles détritiques. La microsonde révèle une grande variation du chimisme de ces spinelles.Plus de la moitié des 134 grains analysés contiennent plus de 50% en poids de Cr₂O₃. La teneur en Al₂O₃ est enversement proportionnelle à celle en Cr₂O₃ et atteint 40 % en poids. Les teneurs en MgO sont à quelques exceptions près plus petites que celles en FeO; les deux éléments ont une corrélation négative. Les teneurs en Fe₂O₃, déterminées dans un quart des grains, ne dépassent généralement pas 5 % en poids. En plus de Cr, Al, Fe, Mg, on rencontre, dans quelques spinelles, des teneurs mesurables en TiO₂.La composition chimique des spinelles détritiques permet de leur assigner comme origine des péridotites appartenant à une série ophiolitique de type alpin.Les études sédimentologiques montrent que la région d'origine des sédiments clastiques du Dévonien moyen se trouve au nord du Massif Schisteux Rhénan.

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/ / , 675 . . . . . 134 50 -% r₂₃. l₂₃ 40 .-%. MgO, , , FeO. . F₂₃, , 5 -%. , , iO. — , . , .

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Regional effects of climate change on reindeer: a case study of the Muotkatunturi region in Finnish Lapland   总被引：2，自引：0，他引：2  

Susan E. Lee  Malcolm C. Press  John A. Lee  Tim Ingold  Terhi Kurttila 《Polar research》2000,19(1):99-105

Few studies have investigated current climate changes for high latitude regions, and the impact of such changes on reindeer and indigenous people. Previous work by other authors has identified snow and ice conditions in winter as being critical in determining the availability of forage for reindeer. Deep snow makes it difficult to access food. Lack of food weakens the herd and can reduce the allocation of nutrients to the development of the foetus in the female deer. Climate data for Lapland, northern Finland, and Karasjok, northern Norway, are examined, together with reindeer calf numbers for the period 1977 to 1994 for the Muotkatunturi region (68°N 25°30'E). Between 1883 and 1993, precipitation increased but temperatures showed no clear warming or cooling trend. However, since the late 1980s, temperatures have increased. A regression analysis on the climate and reindeer data found that the warmer the winter prior to the rut, the fewer the live calves recorded the following year (r = 0.529, p < 0.05). Also, the wetter the winter prior to the rut, the fewer the calves recorded (r = 0.427, p < 0.10). In contrast, the warmer the autumn prior to their birth, the greater the number of calves recorded (r = 0.474, p < 0.10). These results suggest that as climate changes and winters become warmer and wetter with increased snowfall, calf numbers will decline. These findings have important implications for the Saami people who are heavily dependent on the reindeer for their livelihood.  相似文献   

Spatial and temporal variability in the responses of Arctic terrestrial ecosystems to environmental change     

Terry V. Callaghan  Malcolm C. Press  John A. Lee  David L. Robinson  Clive W. Anderson 《Polar research》1999,18(2):191-197

This paper compares the responses of two contrasting Arctic ecosystems to climate change simulations: a polar semi-desert (in Svalbard) and a dwarf shrub heath (at Abisko, northern Sweden). These ecosystems are located close to the northern-and southernmost extremes of the Arctic region, respectively. Inmacts of simulated climatic changes were determined through factorial perturbation experiments, where growing season temperature, nutrient availability and water supply were manipulated. The results are compared with the impact of interannual variation in climate on the growth of a keystone moss species, Hylocomium splendens , from the wider circumpolar area. The perturbation studies revealed that current interannual variability in temperature and the temperate tolerance of many species may exceed predicted changes in mean summer temperature over the next century. Arctic ecosystems differed in their responses to environmental manipulations, with the structure of the dwarf shrub health being affected through shifts in competitive hierarchy, potentially leading to lower biodiversity, and the polar semi-desert being affected through invasion, potentially leading to higher diversity. H. splendens showed negative responses to perturbation at the sub-Arctic site, in contrast to the positive relationship between temperature and growth observed in the natural environment. This apparent discrepancy may result from: (i) artefacts arising from the perturbations, such as lower atmospheric relative humidity; (ii) non-equilibrium responses during the relatively short-term perturbation studies and/or (iii) ecotypic variation in the moss population. Thus, caution should be employed when extrapolating from perturbations studies to both longer time-scales and different ecosystems within the Arctic.  相似文献