On the spectral dissipation of ocean waves due to white capping     

Klaus Hasselmann 《Boundary-Layer Meteorology》1974,6(1-2):107-127

Summary The effect of white capping on the spectral energy balance of surface waves is investigated by expressing the white-cap interactions in terms of an equivalent ensemble of random pressure pulses. It is shown first that the source function for any non-expansible interaction process which is weak-in-the-mean is quasi-linear. In the case of white capping, the damping coefficient is then shown to be proportional to the square of the frequency, provided the wave scales are large compared with the white-cap dimensions. The remaining free factor is determined indirectly from consideration of the spectral energy balance. The proposed white-capping dissipation function is consistent with the structure of the energy balance derived from JONSWAP, and the existence of a ^–5 spectrum governed by a non-local energy balance between the atmospheric input, the nonlinear energy transfer and dissipation. However, closure of the energy balance involves hypotheses regarding the structure of the atmospheric input function which need to be tested by further measurements. The proposed set of source functions may nevertheless be useful for numerical wave-prediction. According to the model, nearly all the momentum transferred across the air-sea interface enters the wave field. For fetchlimited and fully developed spectra in a stationary, uniform wind field, the drag coefficient remains approximately constant. However, for more general wind conditions, this will not be the case and the wave spectrum should be included in an accurate parameterisation of the air-sea momentum transfer.Contribution from the Sonderforschungsbereich Meeresforschung Hamburg of the Deutsche Forschungsgemeinschaft.  相似文献   

Geochemical tables: H. J. Rösler and H. Lange. Elsevier,Amsterdam, 1972, 468 pp. Translated from German by H. Liebscher. $27.95 U.S.A.     

Klaus Keil 《Geochimica et cosmochimica acta》1974,38(8):1324

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Variability and propagation of Labrador Sea Water in the southern subpolar North Atlantic     

Dagmar Kieke  Birgit Klein  Lothar Stramma  Monika Rhein  Klaus Peter Koltermann   《Deep Sea Research Part I: Oceanographic Research Papers》2009,56(10):1656-1674

The variability of two modes of Labrador Sea Water (LSW) (upper and deep Labrador Sea Water) and their respective spreading in the interior North Atlantic Ocean are investigated by means of repeated ship surveys carried out along the zonal WOCE line A2/AR19 located at 43–48°N (1993–2007) and along the GOOS line at about 48–51°N (1997–2002). Hydrographic section data are complemented by temperature, salinity, and velocity time series recorded by two moorings. They have been deployed at the western flank of the Mid-Atlantic Ridge (MAR) in the Newfoundland Basin during 1996–2004. The analysis of hydrographic anomalies at various longitudes points to a gradual eastward propagation of LSW-related signals, which happens on time scales of 3–6 years from the formation region towards the MAR. Interactions of the North Atlantic Current (NAC) with the Deep Western Boundary Current (DWBC) close to Flemish Cap point to the NAC being the main distributor of the different types of LSW into the interior of the Newfoundland Basin. Comparisons between the ship data and the mooring records revealed that the mooring sites are located in a region affected by highly variable flow. The mooring time series demonstrate an elevated level of variability with eddy activity and variability associated with the NAC considerably influencing the LSW signals in this region. Hydrographic data taken from Argo profiles from the vicinity of the mooring sites turned out to mimic quite well the temporal evolution captured by the moorings. There is some indication of occasional southward flow in the LSW layer near the MAR. If this can be considered as a hint to an interior LSW-route, it is at least of minor importance in comparison to the DWBC. It acts as an important supplier for the interior North Atlantic, distributing older and recently formed LSW modes southward along the MAR.  相似文献   

Characterization of the lithological contact in the shergottite EETA79001—A record of igneous differentiation processes on Mars     

Deon Van Niekerk  Cyrena Anne Goodrich  G. Jeffrey Taylor  Klaus Keil 《Meteoritics & planetary science》2007,42(10):1751-1762

Abstract— Elephant Moraine (EET) A79001 is the only Martian meteorite that consists of both an olivine‐phyric shergottite (lithology A) and a basaltic shergottite (lithology B). The presence of these lithologies in one rock has previously been ascribed to mixing processes (either magmatic or impact‐induced). Here we present data regarding phase changes across the contact between the lithologies. These data show that the contact is gradational and suggest that it is a primary igneous feature consistent with crystallization of a single cooling magma. We present a model to establish a petrogenetic connection between an olivine‐phyric and a basaltic shergottite through differentiation. The model involves the shallow or surface emplacement of a magma that contained pre‐eruptive solids (phenocrysts and minor xenocrysts). Subsequent differentiation via crystal settling and in situ crystallization (Langmuir 1989) resulted in a layered sequence of lithology A overlain by lithology B, with gradations in modal abundance of maskelynite (increasing from A to B) and pigeonite/maskelynite (decreasing from A to B), and a gradational change in pattern of pyroxene zonation (zones of magnesian augite separating magnesian and ferroan pigeonite appear and thicken into B) across the contact. A pigeonite phenocryst‐bearing zone near the contact in lithology B appears to be intermediate between lithology A and the bulk of lithology B (which resembles basaltic shergottite Queen Alexandra Range [QUE] 94201). Re‐examination of Sr isotopic compositions in lithology A and across the contact is required to test and constrain the model.  相似文献   

Rapid invasion of Crassostrea gigas into the German Wadden Sea dominated by larval supply     

G. Brandt  A. Wehrmann  K.W. Wirtz   《Journal of Sea Research》2008,59(4):279-296

Invasions of non-indigenous species into coastal habitats have been a frequent phenomenon in the last decades, sometimes with significant impact on the receiving ecosystem. However, the understanding of the entire process and especially the relative importance of larval supply and local recruitment remains unclear. In this study, we simulate the invasion of a benthic invertebrate into a previously uncolonised habitat over several years and validate the results with field data. Therefore, we present field data from a monitoring programme revealing the rapid invasion of the oyster Crassostrea gigas into the East Frisian Wadden Sea, North Sea, between 2003 and 2005. The applied model combines a simple, spatially-explicit population dynamics model for the adult stage with a particle tracking model for the larval stage of the life cycle. Simulation results are able to reproduce the large-scale pattern of the field data and indicate a domination of larval supply on the population dynamics in the early stage of the invasion. Though monitoring and simulations suggest a single larval source outside the study area in the west, the population dynamics in the eastern part is only explainable with an additional source within the study area attributed to an unintentional input of juveniles by mussel fishery. High sensitivities to uncertain parameters result in distinct deviations between monitoring and simulations at particular sites. Especially the impact of site-specific variations of the post-settlement mortality underlines the variability of local recruitment conditions and indicates the need for spatially resolved information for exact predictions.  相似文献   

Resolving physically and biologically driven suspended particulate matter dynamics in a tidal basin with a distribution-based model   总被引：1，自引：0，他引：1  

Joeran Maerz  Kai Wirtz 《Estuarine, Coastal and Shelf Science》2009

Understanding suspended particulate matter (SPM) dynamics in coastal waters is crucial to assess changes in coastal sediment budgets and biogeochemical fluxes. SPM dynamics are subject to various physical and biological factors and processes such as, e.g. tidal currents and aggregation which can be enhanced by extracellular polymeric substances (EPS) that are produced by algae and bacteria. It is still unclear how the different factors and processes interact and together determine SPM dynamics. To unravel the interacting processes and factors, we propose a new distribution-based modeling approach. Based on the derivation of explicit equations for size distribution characteristics of SPM such as the average radius, we derived a model of reduced complexity characterized by low initialization and parameterization effort as well as low computational cost. The proposed 0D model includes the processes of aggregation and fragmentation due to shear, aggregation due to differential settling, deposition, resuspension and tidal exchange, and describes the evolution of the SPM concentration in the water column linked by the settling velocity to the change of the mass average radius of the aggregate distribution. A systematic parameter variation for critical bottom shear stress of erosion, the size of resuspended aggregates, the fractal dimension, the collision efficiency, and the aggregate strength has been performed and compared to observations in the back-barrier basin of Spiekeroog Island in the German Wadden Sea. This analysis confirms the hypothesis that in winter biological influences on SPM dynamics are smaller compared to summer. This is mainly reflected by a significant shift in the various parameters. We hence conclude that biological control mechanisms have a much more quantitative relevance for SPM dynamics than currently represented by state-of-the-art SPM transport models.  相似文献   

Indication for precession of comet Halley's nucleus from dust tail analysis     

Klaus Beisser 《Earth, Moon, and Planets》1990,48(2):127-137

The distinct structures ta comet Halley's dust tail around the beginning of March 1986 are analyzed by means of a computer simulation based on nucleus data obtained by the Giotto mission. It is shown that the assumption of a considerable free precession is required to understand the ground based dust tail observations from that time supposing a rotational period of some 50 hr. But a precession-free rotation with a period of about 7 days does not contradict an analysis of the dust tail structure. In both cases, an asymmetric distribution of the relevant emission sources is required.  相似文献   

Interannual variability patterns of the world’s total column water content: Amazon River basin     

Isabella Bordi  Roberto De Bonis  Klaus Fraedrich  Alfonso Sutera 《Theoretical and Applied Climatology》2015,122(3-4):441-455

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A composite Fe,Ni‐FeS and enstatite‐forsterite‐diopside‐glass vitrophyre clast in the Larkman Nunatak 04316 aubrite: Origin by pyroclastic volcanism     

Klaus KEIL  Timothy J. McCOY  Lionel WILSON  Jean‐Alix BARRAT  Doug RUMBLE  Matthias M. M. MEIER  Rainer WIELER  Gary R. HUSS 《Meteoritics & planetary science》2011,46(11):1719-1741

Abstract– We studied the mineralogy, petrology, and bulk, trace element, oxygen, and noble gas isotopic compositions of a composite clast approximately 20 mm in diameter discovered in the Larkman Nunatak (LAR) 04316 aubrite regolith breccia. The clast consists of two lithologies: One is a quench‐textured intergrowth of troilite with spottily zoned metallic Fe,Ni which forms a dendritic or cellular structure. The approximately 30 μm spacings between the Fe,Ni arms yield an estimated cooling rate of this lithology of approximately 25–30 °C s^?1. The other is a quench‐textured enstatite‐forsterite‐diopside‐glass vitrophyre lithology. The composition of the clast suggests that it formed at an exceptionally high degree of partial melting, perhaps approaching complete melting, and that the melts from which the composite clast crystallized were quenched from a temperature of approximately 1380–1400 °C at a rate of approximately 25–30 °C s^?1. The association of the two lithologies in a composite clast allows, for the first time, an estimation of the cooling rate of a silicate vitrophyre in an aubrite of approximately 25–30 °C s^?1. While we cannot completely rule out an impact origin of the clast, we present what we consider is very strong evidence that this composite clast is one of the elusive pyroclasts produced during pyroclastic volcanism on the aubrite parent body ( Wilson and Keil 1991 ). We further suggest that this clast was not ejected into space but retained on the aubrite parent body by virtue of the relatively large size of the clast of approximately 20 mm. Our modeling, taking into account the size of the clast, suggests that the aubrite parent body must have been between approximately 40 and 100 km in diameter, and that the melt from which the clast crystallized must have contained an estimated maximum range of allowed volatile mass fractions between approximately 500 and approximately 4500 ppm.  相似文献   

EC 11481–2303—a peculiar subdwarf OB star revisited     

Thomas Rauch  Klaus Werner  Jeffrey W. Kruk 《Astrophysics and Space Science》2010,329(1-2):133-139

EC?11481–2303 is a peculiar, hot, high-gravity pre-white dwarf. Previous optical spectroscopy revealed that it is a sdOB star with T _eff=41?790 K, log?g=5.84, and He/H = 0.014 by number. We present an on-going spectral analysis by means of non-LTE model-atmosphere techniques based on high-resolution, high-S/N optical (VLT-UVES) and ultraviolet (FUSE, IUE) observations.We are able to reproduce the optical and UV observations simultaneously with a chemically homogeneous NLTE model atmosphere with a significantly higher effective temperature and lower He abundance (T _eff=55?000 K, log?g=5.8, and He/H=0.0025 by number). While C, N, and O appear less than 0.15 times solar, the iron-group abundance is strongly enhanced by at least a factor of ten.  相似文献