Summary A brief survey is given of environmental factors influencing turbidity: tides, vertical stratification, seasonal factors, state of sea. Observations of Secchi disc visibility, averaged per half-degree, square, are compared with surface readings of beam attenuation of the seawater. Considering also results of measurements of daylight penetration in the North Sea, a thumb rule is found for the depth of the level of 1% daylight intensity, viz. three times the Secchi dept. For the southern North Sea it is possible to indicate lines of equal mean depth of that level during the periods December/May and June/November.
Die Trübung der südlichen Nordsee
Zusammenfassung Es wird ein kurzer Überblick der die Trübung beeinflussenden Umweltsbedingungen gegeben: Tiden, vertikale Schichtung, jahreszeitliche Faktoren, Zustand der Meeresoberfläche. Beobachtungen der Durchsichtigkeit mit Hilfe von Secchi-Scheiben, gemittelt über Halbgradfelder werden verglichen mit Oberflächenmessungen der Lichtabschwächung des Seewassers. Unter Berücksichtigung auch von Meßergebnissen von Tageslichtdurchdringung in der Nordsee ist eine Faustregel für die Tiefe auf der Basis von 1% Tageslichtintensität gefunden worden, nämlich das Dreifache der Secchi-Tiefe. Für die südliche Nordsee ist es möglich, Linien gleicher mittlerer Tiefen auf dieser Basis während der Perioden Dezember/Mai und Juni/November zu bestimmen.
La turbidité dans la partie Sud de la mer du Nord
Résumé On passe en revue brièvement les facteurs ambiants qui influencent la turbidité: marées, stratification verticale, facteurs saisonniers, état de la mer. Des observations de transparence par disque de Secchi, calculées en moyenne par carré d'un demi-degré, sont comparées avec l'affaiblissement du rayonnement lumineux dans l'eau de mer constaté à la surface. En tenant compte aussi des mesures de la pénétration de la lumière du jour dans la mer du Nord, on établit une loi approximative donnant la profondeur au niveau de laquelle l'intensité de cette lumière est de 1% et qui est trois fois la profondeur de Secchi. Pour la partie Sud de la mer du Nord, il est possible de déterminer des lignes d'égale profondeur moyenne de ce niveau pour les périodes de Décembre à Mai et de Juin à Novembre.
Nach einem Vortrag gehalten auf der ICES-Tagung 1969 in Dublin. 相似文献
Natural Hazards - Climate change leads to sea level rise worldwide, as well as increases in the intensity and frequency of tropical cyclones (TCs). Storm surge induced by TC’s, together with... 相似文献
Summary Five ofBerlage's eight empirical rules concerning the Southern Oscillation (1957) may be united in one general rule with regard to the different influence of solar activity during 11-year sunspot cycles with annual maximum numberR above or below 85 (Tables 2, 3, 4, 5 and 6). The opposite character of strong and weak 11-year cycles of solar activity is also present in the 7-year period (Tables 7, 8, 9 and 10; Fig. 1). Finally it is shown that a similar contrast obviously exists in the appearance of polar lights (Table 11, Fig. 2 and 3).The results have not been statistically tested. Because of the rather small number of solar periods involved and the complicated character of the relations found, I could not find a satisfactory statistical method to operate with. I may emphasize, however, the converging evidence enlarging considerably the statistical significance of my results. 相似文献
The orientation of the straight internal foliation Si within large ( 5 mm) garnet porphyroblasts has been measured relative to the orientation of the external foliation Se around a single antiform of 0.5 m wavelength, which folds the dominant regional foliation. The internal foliation is not constant in orientation, but varies consistently both with position around the fold and with the porphyroblast ellipticity. The dip of Si (hinge dip taken as zero) is consistently less than the dip of Se; it increases with increasing dip of Se and with increasing ellipticity of the porphyroblasts. Si effectively defines a fold with an opening angle greater than that in the external foliation. The opening angle of this fold in Si decreases with increasing porphyroblast ellipticity. The observed variation in the orientation of Si can be explained qualitatively by a flattened flexural flow model for fold development, as could be expected for folding of a pre-existing, strongly anisotropic foliation. The measurements clearly demonstrate that rotation of porphyroblasts relative to geographical co-ordinates did occur during the development of this fold and that a model based on the classical theories of rotation of stiff inclusions in a weaker viscous matrix is most appropriate. 相似文献
In this study, we address the effective method to apply a novel reliability method integrated with finite element models to
the safety assessment of pilot site Scheldt in the Netherlands. This site was considered as one of the three main pilot sites
in Europe to assess the application of newly suggested techniques in order to reduce and manage the flood risk in the Floodsite
project. , 2004–2009). The novel method of dynamic bounds (DB) is applied to this site after a successful experience in (Rajabalinejad in Reliability
methods for finite element models, 1 edn. IOS Press, Amsterdam, 2009). In this study, the bi-functional response of the finite element model is considered, and the dimensional uncertainty is
defined presenting the expected uncertainty for a certain dimension in the DB method. The uncertainty is used as a judgment
tool to choose the dimension for the DB method for the desired accuracy. The results obtained by applying this technique are
presented in this paper. 相似文献
Particularly in arid and semiarid areas, more and more populations rely almost entirely on imported water. However, the extent to which intentional discharge into transiting river
systems and unintentional leakage may be augmenting water resources for communities along and down gradient of the water transfer scheme has not previously been subject to research. The objective of this study was to assess both the potential of a large-scale water
transfer (WT) scheme to increase groundwater availability by channel transmission losses in a large dryland aquifer system (2,166 km²) in Brazil, and the capability of the receiving streams to transport water downstream under a prolonged drought. An integrated surface-water/groundwater model was developed to improve the estimation of the groundwater resources, considering the spatio-temporal variability of infiltrated rainfall for aquifer
recharge. Aquifer recharge from the WT scheme was simulated under prolonged drought conditions, applying an uncertainty analysis of the most influential fluxes and parameters. The annual recharge (66 mm/year) was approximately twice the amount of water abstracted
(1990–2016); however, the annual recharge dropped to 13.9 mm/year from 2012 to 2016, a drought period. Under similar drought conditions, the additional recharge (6.89 × 106 m³/year) from the WT scheme did not compensate for the decrease in groundwater head in areas that
do not surround the receiving streams. Actually, the additional recharge is counteracted by a decrease of 25% of natural groundwater recharge or an increase of 50% in pumping rate; therefore, WT transmission losses alone would not solve the issue of the unsustainable management of groundwater resources.
Although most GIS-based planning support have the capacity to show the location and attributes of different places, very few GIS-based systems are able to describe adequately the degree of spatial interaction, or the geographic accessibility, between places. The Faculty of Geographical Sciences of the Utrecht University (The Netherlands) and the South African Council for Scientific and Industrial Research (CSIR), are developing a methodology to address the problem of measuring accessibility by integrating specialised GIS software (FlowMap) that measures the geographic accessibility between locations within a spatial decision support system (AccessMap). The resulting GIS-tool is applied to the Wild Coast area in South Africa. In this region a lack of accessibility to market centres is perceived as one of the major constraints of economic development in the region. 相似文献
The 50-year global CO2 record led the way in establishing a scientific fact: modern civilization is changing important properties of the global
atmosphere, oceans and biosphere. The evidence on which this scientific fact is based will be refined further, but the next
challenge for scientists is broader. In addition to its traditional role in providing discovery, diagnosis, and prediction
of the changes that are taking place on our planet, science has now also a role in helping society mitigate emissions by objectively
quantifying them, and in helping adaptation by providing environmental forecasts on regional scales. Science is also expected
to provide new options for society to tackle the transition to a new energy system, and to provide thorough environmental
evaluation of all such options. This is what the meeting recognized as planetary responsibilities for scientists in the next
50 years. 相似文献