Summer distribution of dissolved Cd,Co, Cu,Mn, and Ni in central North Sea waters     

Dr. Klaus Kremling  Alfred Wenck  Christa Pohl 《Ocean Dynamics》1987,40(3):103-114

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Evolution of the oceanic plankton     

Helen Tappan  Alfred R. Loeblich 《Earth》1973,9(3):207-240

In its evolution through geologic time, the oceanic plankton has reflected many changes in the physical environment while both causing and being affected by evolutionary change in the associated biota. Temporal variations in the vertical and latitudinal habitat partitioning also affected geochemical balances in the oceans and accumulation rates of biogenic sediments, and perhaps the atmospheric oxygen pressure. Advantages of the oceanic plankton habitat that led to its occupation by a varied sequence of organisms include its extensive geographic area, the possibility for rapid dispersal by currents, the availability of resources (ranging from light, carbon dioxide, and dissolved nutrients for the autotrophic organisms to the various lower trophic levels required by the heterotrophs), and the better oxygenation of the upper water layers.Convergent morphology of the plankton represents adaptations for suspension in the water column, for movement within this water mass to increase nutrient uptake, and for protection against grazing or predation. Necessary attributes for cosmopolitan species include eurythermy and euryhalinity. The patchiness of plankton diversity results from small-scale variations in water masses, the low level of interorganism contact or competition, and the possibility of rapid exploitation of favorable conditions by species present in the local area.Parallel evolution, radiation, and extinction of the various components of the oceanic plankton are similar in pattern to an ecologic succession — early evolution and conditions following major periods of extinction being homologous with the physically controlled or immature modern ecosystem associated with high stress levels and characterized by high net but low gross productivity, low diversity but great intraspecific variability, and small biomass. Evolutionary radiation is associated with more stable physical conditions and, like the seral progression, of an ecosystem, results in high diversity but less intraspecific variability. Increased biological interaction leads to higher gross but lower net productivity, hence more efficient energy and resource utilization. The drop in gross oceanic productivity at times of major extinction is associated with low diversity and decreased rate of accumulation of biogenic ooze, hence the apparent worldwide disconformities, as at the Cretaceous-Tertiary boundary, even in the deep sea.  相似文献   

Applications of an orbiting gravity gradiometer     

Oscar L. Colombo  Alfred Kleusberg 《Journal of Geodesy》1983,57(1-4):83-101

Considering present attempts to develop a gradiometer with an accuracy between 10⁻³ E and 10⁻⁴ E, two applications for such a device have been studied: (a) mapping the gravitational field of the Earth, and (b) estimating the geocentric distance of a satellite carrying the instrument. Given a certain power spectrum for the signal and 10⁻⁴ E (rms) of white measurement noise, the results of an error analysis indicate that a six-month mission in polar orbit at a height of 200 km, with samples taken every three seconds, should provide data for estimating the spherical harmonic potential coefficients up to degree and order 300 with less than 50% error, and improve the coefficients through degree 30 by up to four orders of magnitude compared to existing models. A simulation study based on numerical orbit integrations suggests that a simple adjustment of the initial conditions based on gradiometer data could produce orbits where the geocentric distance is accurate to 10 cm or better, provided the orbits are 2000 km high and some improvement in the gravity field up to degree 30 is first achieved. In this sense, the gravity-mapping capability of the gradiometer complements its use in orbit refinement. This idea can be of use in determining orbits for satellite altimetry. Furthermore, by tracking the gradiometer-carrying spacecraft when it passes nearly above a terrestrial station, the geocentric distance of this station can also be estimated to about one decimeter accuracy. This principle could be used in combination with VLBI and other modern methods to set up a world-wide 3-D network of high accuracy.  相似文献   

Urban vulnerability and adaptation to heatwaves: a case study of Graz (Austria)     

Christiane Reischl  Romana Rauter  Alfred Posch 《Climate Policy》2018,18(1):63-75

The increasing frequency of heatwaves, particularly in urban contexts, is one of the perceptible consequences of climate change. A city’s vulnerability to these heatwaves must be determined to develop proper adaptation measures. This article addresses the vulnerability of a medium-sized city in Central Europe, Graz, to heatwaves. Based on secondary data and primary data gathered from expert interviews, we identified certain determinants of vulnerability for the city: temperature, proportion of open and green spaces to developed areas, construction period of buildings, distribution of age and poverty risk, adaptation strategies used, and risk perception levels assessed for decision makers in the city administration. Certain city districts can be classified as particularly vulnerable. A high level of risk perception was detected among all decision makers and some adaptation measures have already been enacted. In particular, inter-organizational collaboration in adaptation networks works effectively. A deficit in efficient communication between researchers, policy makers, and members of the public was perceived to be the main barrier. This case study exemplifies the assessment of a city’s vulnerability to heatwaves on the basis of particular determinants and can be applied to many other cities.

Policy relevance

The method applied revealed potential improvements and opportunities on the policy level. Strong networks for climate change adaptation are most effective if regular meetings take place, allowing trust and friendship to grow between decision makers. More target-group-oriented information is needed. Emergency organizations, in particular, need more information, because the perception of heatwave risks has only been based thus far on personal experiences. By establishing a central authority, more information could be provided on heatwaves in cities. The need to raise the perception of members of the population and motivate them to take personal responsibility during disasters was emphasized by interviewed decision makers. This can be supported by providing advice during heatwaves through newspapers, TV, and radio. People in risk groups and their relatives could be trained in workshops. City areas that are at high risk should be marked on maps to make relevant information more tangible for decision makers.  相似文献   

Extreme events of stratospheric stationary waves and indications for stratosphere–troposphere coupling: simultaneous analysis in boreal winter     

Jianjun Xu  Alfred M. Powell Jr 《Theoretical and Applied Climatology》2015,120(3-4):661-671

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