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1.
Russell A. Moll Alan Bratkovich William Y. B. Chang Peimin Pu 《Estuaries and Coasts》1993,16(1):92-103
An investigation of the thermal front in southeastern Lake Michigan during April 1988 revealed a dynamic physical, chemical, and biological environment. The front was observed approximately 4 km from the coast as a distinct gradient separating cold open-lake waters from warmer nearshore waters. Surface isotherms near the front were generally parallel to one another but skewed with respect to shore. Comparison between April 22 and 29 showed that the surface isothern pattern was modulated by wind stress. The pattern from April 29 showed signs of flow instabilities with horizontal scales of 1 km to 5 km. Surface drifter trajectories provided estimates of horizontal convergence at the fron which varied from 7×10?6 s?1 to 20×10?6 s?1. Inferred rates of downwelling, which ranged from 9.5 m d?1 to 20.7 m d?1, were sufficient to move a water parcel from the surface to the bottom in 2 to 6 d at the front. Convergent circulation was observed on both sampling dates despite contrasts in wind stress. Concentrations of chloride, soluble silica, and chlorophyll, which were always higher inshore, were 5% to 82% larger than offshore mean values. The aquatic environment just inshore of the thermal front was characterized by chlorphyll concentrations which exceeded 5.0 μg 1?1 while concentrations offshore were between 1.0 μg 1?1 and 2.0 μg 1?1. A relatively uniform vertical structure in chlorophyll concentrations in the frontal zone was consistent with the observed convergence and inferred downwelling near the front. 相似文献
2.
Jesus A. Uriarte Laura Damas Mollá Maialen Sagarna Arantza Aranburu Francisco García Iñaki Antigüedad Tomás Morales 《水文研究》2020,34(4):1004-1015
Locating and quantifying groundwater flow in many built-up areas are a priority with regard to its complete restoration. In this work, a hydrogeological survey of the surroundings of the Punta Begoña Galleries (Getxo, Bizkaia), built on a coastal cliff, was completed by using ground penetrating radar (GPR) testing. Thus, the preliminary characterization of soils and rocks in accessible areas of the cliff was first improved by hydrogeological information gathered from a single survey borehole, including permeability measurements by low pressure injection tests (LPTs) and continuous water level monitoring. As a complementary method, the non-destructive GPR technique was performed during both dry and wet hydrological periods and in tandem with the injection tests, providing more complete spatial and temporal images of water flows. Specifically, GPR allows mapping of flow paths in soils and assessing the continuity of fractures in rock masses. Altogether, this complementary approach provides greater knowledge of complex underground flow dynamics in built environments, thus making it easier to make decisions for their management. 相似文献
3.
Variabilität der Primärproduktion aus dreidimensionalen Modellrechnungen für die Nordsee mit ECOHAM1
Ocean Dynamics - Mit dem dreidimensionalen Modell ECOHAM1 (Ecological North Sea Model, Hamburg, Version 1) wurde die jährliche Primärproduktion für die Jahre 1985 bis 1994 regional... 相似文献
4.
5.
Al- and Mg-doped titanomagnetites were synthesized at 1300°C using the gas-mixing technique. A composition, representative of average natural titanomagnetites in ocean floor basalts, was sought.
The samples were ball-milled in acetone to average grain sizes of 0.5 μm and 5 μm and the material was then oxidised, in air, at temperatures below 300°C. This procedure formed titanomaghemite, a cation-deficient titanomagnetite.
Low-temperature oxidation is described as the diffusion of Fe-ions out of the spinel lattice and the process is observed to be distinctly dependent upon grain size. 相似文献
6.
Summary The mean annual cycle of the net energy flux through the sea surface and of the heat storage are investigated in detail using
observations of the Light Vessel LV Elbe 1 for the period 1962-1986 in the German Bight and at Ocean Weather Ship OWS Famita
for the period 1965-1978 in the central North Sea. The investigation confirms the general geographical picture of the heat
budget of the German Bight that shows a net loss to the atmosphere by a long-term mean of -15 W m-2. The radiative surface input of 113 W m-2 is balanced by -62 W m-2 net back radiation, -51 W m-2 of latent heat flux and -15 W m-2 of sensible heat flux. The heat advection calculated as the residual of the heat storage rate and surface energy balance
is 16 W m-2. The mean annual cycles of heat storage and surface energy balance are nearly equal, and the temperature variations are mainly
driven by local heat input. The small differences build up the annual advection cycle. Warm water advection occurs from October
to April and cold water advection in summer from May to September. The seasonal advection variability is extreme in winter
and summer, and the ranges slow down in spring and autumn, when the sign of the heat balance changes. The OWS Famita is situated
also in an area of net energy loss to the atmosphere, showing a long-term annual mean loss of -16 W m-2. The surface radiation input of 105 W m-2 is mainly balanced by outgoing long wave back radiation of -60 W m-2 and a latent heat flux of -49 W m-2. A minor contribution to the heat balance is the sensible heat flux of -12 W m-2. Warm water advection occurs in winter and spring. Variability is greater than at LV Elbe 1.
Calculated monthly fluxes show the dominance of the energy gain of incoming solar radiation. Net long-wave radiation is nearly
constant with time. The sensible heat flux serves as a heat source only at LV Elbe 1 from May to June. The latent heat flux
is a loss term all the year. The heat storage cycle is nearly equal to the surface energy balance at LV Elbe 1 ; the differences
are more irregular at OWS Famita. The temperature variations are mainly driven by local heat input. The simplified one-dimensional
balance holds generally for the heating period in both regions, although for some months the magnitude of the advection is
up to a third of the net surface fluxes or the storage rate. At LV Elbe 1 from April to December, the heat budget is dominated
by local dynamics. At OWS Famita the advective contribution is less than 30% of net surface heat input from May to October.
The dominance of solar radiation in determining the surface heat fluxes, and the annual cycles of the storage rate in phase
justify the use of one-dimensional models as a first approximation of the temperature dynamics in these regions. Comparisons
of simulations of the temperature cycle at both sites with observations give sufficient precision during most parts of the
seasonal cycle. Suitable data sets to drive and validate these models are now available and different models should be tested.
Advektive beitr?ge zur w?rmebilanz der deutschen bucht (feuerschiff elbe 1) und zur w?rmebilanz der zentralen nordsee (Wetterschiff Famita)
Zusammenfassung Untersucht wurde der mittlere Jahresgang vom W?rmeeintrag durch die Meeresoberfl?che und vom W?rmeinhalt der Wassers?ule. Dazu wurden Messungen aus der Deutschen Bucht vom Feuerschiff Elbe 1 für die Jahre 1962-1986 und Messungen in der zentralen Nordsee vom Wetterschiff Famita für die Jahre 1965-1978 verwendet. Die Untersuchung best?tigt das generelle Bild einer W?rmeabgabe an die Atmosph?re von -15 W m-2 im langj?hrigen Mittel für die Deutsche Bucht. Die kurzwellige Einstrahlung von 113 W-2 wird durch -62 W m-2 langwellige Ausstrahlung, -51 W m-2 latenten W?rmefluβ und -15 W m-2 sensiblen W?rmefluβ nahezu balanciert. Die berechnete W?rmeadvektion als Residuum aus W?rmeinhalt und Nettow?rmefluβ an der Meeresoberfl?che betr?gt 16 W m-2 Der Jahresgang des W?rmeinhaltes und der Jahresgang des Nettow?rmeflusses an der Oberfl?che sind fast gleich, so daβ der Temperaturjahresgang haupts?chlich durch den lokalen W?rmeeintrag gesteuert wird. Kleine Abweichungen hiervon bestimmen den Jahresgang der W?rmeadvektion. Warmwasseradvektion tritt von Oktober bis April auf. Kaltwasseradvektion liegt im Sommer von Mai bis September vor. Die Variabilit?t der W?rmeadvektion ist im Winter und Sommer am gr?βten, w?hrend die Variabilit?t im Frühjahr und Herbst geringer ist, wenn sich das Vorzeichen der W?rmebilanz ?ndert. Das Wetterschiff Famita befindet sich ebenfalls in einer Region, in der W?rme an die Atmosph?re abgegeben wird. Die W?rmeabgabe betr?gt -16 W m-2 im langzeitlichen Mittel. Die kurzwellige Einstrahlung von 105 W m-2 wird haupts?chlich durch -60 W m-2 langwellige Ausstrahlung, -49 W m-2 latenten W?rmefluβ und -12 W m-2 sensiblen W?rmefluβ balanciert. Warmwasseradvektion tritt im Winter und Frühjahr auf. Die Variabilit?t der W?rmeadvektion ist gr?βer als bei Feuerschiff Elbe 1. Die berechneten monatlichen Energieflüsse zeigen, daβ die solare Einstrahlung den Jahresgang der W?rmebilanz dominiert. Die effektive Ausstrahlung ist nahezu konstant. Die sensible W?rme wirkt nur bei Feuerschiff Elbe 1 von Mai bis Juni als W?rmequelle. Der latente W?rmefluβ ist w?hrend des gesamten Jahres negativ. Für Feuerschiff Elbe 1 ist der W?rmeinhalt der Wassers?ule mit dem Energieeintrag an der Oberfl?che in Phase, w?hrend bei Wetterschiff Famita Differenzen auftreten. Die Temperaturvariationen sind haupts?chlich durch den lokalen W?rmeeintrag bestimmt. Diese vereinfachten Verh?ltnisse gelten für beide Regionen, obwohl für einige Monate die W?rmeadvektion bis zu einem Drittel des Nettow?rmeflusses an der Oberfl?che betragen kann. Bei Feuerschiff Elbe 1 wird die W?rmebilanz von April bis Dezember durch die lokale Dynamik bestimmt. Bei Wetterschiff Famita ist die W?rmeadvektion von Mai bis Oktober kleiner als 30% vom Oberfl?cheneintrag. Die Dominanz der solaren Einstrahlung für die W?rmebilanz an der Oberfl?che und der phasengleiche Jahresgang des W?rmeinhaltes rechtfertigen es, eindimensionale Wassers?ulenmodelle für die Region zu verwenden, um die Dynamik der Temperatur zu berechnen. So zeigt der Vergleich von simulierten und gemessenen Temperaturjahresg?ngen an beiden Positionen eine ausreichende Genauigkeit über weite Teile des Jahres. Damit stehen neben der gezeigten W?rmebilanzabsch?tzung zwei Datens?tze zur Verfügung, um Modelle zu betreiben, zu validieren und verschiedenartige Modelle zu vergleichen.相似文献
7.
The distribution of element abundances with redshift in Damped Lyα (DLA) systems can be adequately reproduced by the same
models reproducing the halo and disk components of the Milky Way Galaxy at different galactocentric distances. In this sense,
DLA systems are well represented by normal spiral galaxies in their early evolutionary stages.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
8.
A generalization of the multiphase chemical evolution model applied to a wide set of theoretical galaxies is shown. This set
of models has been computed by using the so-called Universal Rotation Curve from (Persic, Salucci and Steel, 1996) to calculate
the radial mass distributions of each theoretical galaxy. By assuming that the molecular cloud and star formation efficiencies
depend on the morphological type of each galaxy, we construct a bi-parametric grid of models whose results are valid in principle
for any spiral galaxy, of given maximum rotation velocity or total mass, and morphological type.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
9.
We have computed a set of multiphase chemical evolution models in which the radial mass distributions of each theoretical
galaxy is calculated using the universal rotation curve from Persic, Salucci and Steel (1996). We obtain the chemical evolution
for galaxies of different masses and morphological types by changing the efficiencies to form molecular clouds and stars according
with these types. We obtain the radial distributions of diffuse and molecular gas densities, the star formation rate and abundances
for 15 elements for each galaxy.
This revised version was published online in September 2006 with corrections to the Cover Date. 相似文献
10.
Leif M. Petersen Andrew J. E. Charman Eugene J. Moll Ray J. Collins Marc T. Hockings 《社会与自然资源》2014,27(3):315-336
South Africa's organically emerged cultural business of traditional healing is almost exclusively reliant on wild-harvested resources extracted from wilderness areas or open-access commons. The wild medicine business has been described for much of South Africa, although is little understood in Cape Town, the urban centerpiece of the Cape Floristic Region (CFR). A census of different traditional healer typologies in five typical working-class residential areas (representing ～71,500 residents) was conducted to assess the nature and extent of traditional medicine harvesting and trade. Extrapolating these findings for the city reveals a local industry of more than 15,000 practitioners collectively conducting trade worth US $15.6 million per year. More than 40% of the volume of traditional medicines traded in the city is harvested from the CFR. Future conservation approaches must consider that the business of traditional healing and dispensing wild-harvested medicines is both economically important and culturally entrenched. 相似文献