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981.
982.
This paper considers the results of numerical experiments involving POLYMODE data assimilation by a barotropic model for synoptic ocean dynamics. The model's response the data assimilation for various space-time discretenesses of assimilation is studied. Results derived from the application of optimal interpolation algorithms and modified optimal filtration algorithms are compared. Qualitative similarity to the calculations carried out through the simulation modelling technique is noted. Optimal assimilation algorithms are determined, depending on the space-time discreteness used. An optimal sampling discreteness for the POLYMODE conditions is suggested.Translated by Vladimir A. Puchkin. 相似文献
983.
The problem of monitoring of the mesoscale variability of hydrophysical fields in the shelf zone is considered. The usefulness of the data available in regional information centres is discussed. The possibility of monitoring the dynamics of the oceanic fields in the tropical Atlantic encompassing separate observation sites is demonstrated using the oceanographic databank of the scientific research centre (CERESCOR) in Conakry-Rogbane as an example. The results of assimilation of the hydrophysical survey data derived on the shelf in a telescopic model of the region are given.Translated by Mikhail M. Trufanov. 相似文献
984.
M. Taviani 《Geo-Marine Letters》1994,14(2-3):185-191
Recent suggestions that the Miocene-age calcari aLucina blocks scattered in the Apennine chain of the Italian peninsula are methanogenic in nature (paleo cold vents) calls for a reexamination of their macrofauna. Two Tortonian-age outcrops of such limestones (Case Rovereti and Montepetra) have been analyzed for their mollusk content and shown to host a diverse vent fauna. The paleoassemblages show remarkable similarities with modern counterparts associated with hydrocarbon venting on the Gulf of Mexico continental slope. Faunal data from both sites lend support to the hypothesis that methane/hydrocarbon venting was active during the Miocene and sustained specialized bathyal chemosynthetic communities in the ancient Mediterranean. 相似文献
985.
986.
A hybrid thermal protection method using waste heat from a surface-mounted outboard motor is shown to create a warm “micro-climate” environment for divers. The effects of surface heater capacities, water flow rates, shelter volume and shelter insulation on micro-climate temperatures are characterized. During long, cold-water decompression stops this method offers a reliable, low-cost alternative to surface-supplied hot water suits or diver-carried heating systems. An added bonus for divers using closed-circuit breathing apparatus is prolonged durations of their carbon dioxide scrubbers when surrounded by the warm water “micro-climate”. Closed-circuit and open-circuit options of this diver decompression shelter concept are evaluated. 相似文献
987.
988.
Thomas F. Wever Hannelore M. Fiedler Gunther Fechner Friedrich Abegg Ingo H. Stender 《Geo-Marine Letters》1997,17(4):246-252
Between 2 and 6 February, 1995, a 25 km2 area at the Dry Tortugas (Florida Keys) was surveyed with a 100 kHz side-scan sonar system and 3.5-kHz subbottom profiler.
The side-scan system revealed a pattern of alternating high and low backscatter. The subbottom profiler showed areas with
no acoustic penetration between sediment troughs. The combination of both methods allowed delineation of the boundaries in
high-backscatter regions, and sediment samples allowed correlations between high backscatter and coarser-grained sediments. 相似文献
989.
In the frame of the linear theory for long waves, the paper studies long waves generated by a barotropic tide running at an
arbitrary angle over a bottom ridge. The ocean is assumed to be two-layered. In the area of a ridge with a rectangular cross
section, geostrophic flows are considered, coupled with the inclinations of the free surface and interface. Wave amplitudes
are shown to depend on the angle of an onrunning tide and this allows us to reach a conclusion about the influence of a geostrophic
current on the generation of internal waves.
Translated by Vladimir A. Puchkin. 相似文献
990.
Geoacoustic and physical properties of carbonate sediments of the Lower Florida Keys 总被引:4,自引:0,他引:4
Near-surface sediment geoacoustic and physical properties were measured from a variety of unconsolidated carbonate sediments
in the Lower Florida Keys. Surficial values of compressional and shear speed correlate with sediment physical properties and
near-surface acoustic reflectivity. Highest speeds (shear 125–150 m s-1; compressional 1670–1725 m s-1) are from sandy sediments near Rebecca Shoal and lowest speeds (shear 40–65 m s-1; compressional 1520–1570 m s-1) are found in soft, silty sediments which collect in sediment ponds in the Southeast Channel of the Dry Tortugas. High compressional
wave attenuation is attributed to scattering of acoustic waves from heterogeneity caused by accumulation of abundant shell
material and other impedance discontinuities rather than high intrinsic attenuation. Compared to siliciclastic sediments,
carbonate sediment shear wave speed is high for comparable values of sediment physical properties. Sediment fabric, rather
than changes due to the effects of biogeochemical processes, is responsible for these differences. 相似文献