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51.
The scaling law linking the strength of the meridional overturning to the surface meridional temperature gradient is re-examined in two ocean general circulation models at coarse resolution in an idealised single-hemisphere setting. Two sets of results are presented, where the surface meridional temperature gradient is decreased either by increasing the northernmost temperature and keeping the equator temperature fixed, or by decreasing the equator temperature and keeping the northernmost temperature fixed. The maximum of the meridional overturning first increases and then decreases when the northernmost temperature is gradually increased, whereas the maximum overturning decreases monotonically when the equator temperature is decreased. No scaling law can be derived when the northernmost temperature is increased, whereas a 2/3 power law is found when the temperature is decreased at the equator. The behaviour of the overturning is strongly influenced by the vigour and, particularly, the spatial patterns of convection, which vary substantially between the two sets and which control the horizontal and vertical density gradients at high latitudes. 相似文献
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Meena Sansar Raj Soares Lucas Pedrosa Grohmann Carlos H. van Westen Cees Bhuyan Kushanav Singh Ramesh P. Floris Mario Catani Filippo 《Landslides》2022,19(5):1209-1229
Landslides - Event-based landslide inventories are essential sources to broaden our understanding of the causal relationship between triggering events and the occurring landslides. Moreover,... 相似文献
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Since 1998, ferry observations have been carried out in the Marsdiep tidal inlet (Dutch Wadden Sea), using amongst other instruments a vessel-mounted acoustic Doppler current profiler (ADCP). Besides 32 cross-sections a day of current velocity data, the instrument also records the echo intensity, which has been interpreted in terms of suspended sediment concentration (SSC) before (Thorne and Hanes, Cont Shelf Res 22:603–632, 2002). However, we show herein that the random phase scattering model as outlined by Thorne and Hanes (Cont Shelf Res 22:603–632, 2002), predicts unrealistically high values of SSC if the depth-averaged current velocity exceeds approximately 0.7 m/s. Therefore, we extended the random phase scattering model by including scattering by turbulence-induced variability in SSC. The important mechanism is that when SSC fluctuations are present at length, scales of the order of the acoustic wavelength, the phase of the returned signal is no longer random and causes stronger backscatter. Such SSC fluctuations occur as a result of turbulent eddies in combination with an SSC gradient. The extended model was compared with data of two field surveys carried out in the Marsdiep inlet. The extended model, when compared with the classical random phase model, showed a large improvement of accuracy of the estimated SSC, which allows us to apply the model to the ferry data set to analyse suspended sediment transports through the Marsdiep tidal inlet. 相似文献
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Rutger de Wit Lucas J. Stal Bente Aa. Lomstein Rodney A. Herbert Hans van Gemerden Pierluigi Viaroli Victor-Ugo Cecherelli Francisco Rodríguez-Valera Marco Bartoli Gianmarco Giordani Roberta Azzoni Bart Schaub David T. Welsh Andrew Donnelly Ana Cifuentes Josefa Antn Kai Finster Lise B. Nielsen Anne-Grethe Underlien Pedersen Anne Turi Neubauer Marina A. Colangelo Sander K. Heijs 《Continental Shelf Research》2001,21(18-19)
“Buffer capacities” has been defined in ecology as a holistic concept (e.g., Integration of Ecosystem Theories: A Pattern, second ed. Kluwer, Dordrecht, 1997, 388pp), but we show that it can also be worked out in mechanistic studies. Our mechanistic approach highlights that “buffering capacities” can be depleted progressively, and, therefore, we make a distinction between current and potential “buffering capacities”. We have applied this concept to understand the limited “local stability” in seagrass ecosystems and their vulnerability towards structural changes into macro-algal dominated communities. We explored the following processes and studied how they confer buffering capacities to the seagrass ecosystem: (i) net autotrophy is persistent in Zostera noltii meadows where plant assimilation acts as a sink for nutrients, this contrasted with the Ulva system that shifted back and forth between net autotrophy and net heterotrophy; (ii) the Z. noltii ecosystem possesses a certain albeit rather limited capacity to modify the balance between nitrogen fixation and denitrification, i.e., it was found that in situ nitrogen fixation always exceeded denitrification; (iii) the nitrogen demand of organoheterotrophic bacteria in the sediment results in nitrogen retention of N in the sediment and hence a buffer against release of nitrogen compounds from sediments, (iv) habitat diversification in seagrass meadows provides shelter for meiofauna and hence buffering against adverse conditions, (v) sedimentary iron provides a buffer against noxious sulfide (note: bacterial sulfide production is enhanced in anoxic sediment niches by increased organic matter loading). On the other hand, in the coastal system we studied, sedimentary iron appears less important as a redox-coupled buffer system against phosphate loading. This is because most inorganic phosphate is bound to calcium rather than to iron. In addition, our studies have highlighted the importance of plant–microbe interactions in the seagrass meadows. 相似文献
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Vasile Marza Juraci Carvalho Lucas Barros Cristiano Chimpliganond 《Journal of Seismology》2003,7(1):89-98
An analysis and discussion of the main features and effects of the 1999global seismicity based especially on the inferred patterns of strong(Mw 7) earthquakes using NEIC/USGS data is presented.Based on the above data and their statistical features (see also Table 1)one may state that from the point of view of occurrence rate (number/yr)the 1999 global seismicity was fairly regular, but from the moment (orenergy) release standpoint it is well under the long-term average. The spacepartition was again rather typical and time distribution was quasi-Poissonian,noteworthy, the 1999 worldwide seismicity had an anomalously high deathtoll, to be discussed later. Two main new insights are brought by ouranalysis: (i) a (mega)quiescence along the whole south American segmentof circum-Pacific earthquake belt, which was inferred and rated asanomalous while it was underway and which, in retrospect, ended with thegreat (Mw = 8.4 HRV) 2001 Arequipa (Peru) event; (ii) an intriguingmonotonous rate decrease within only magnitude class 5.0 to 5.9 duringthe analyzed period (i.e., 1990–1999). 相似文献
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Abstract. An object-relational data model is an entry point and integral part of geologic analysis system, in which we can start geologic modeling inside a database. A conceptual data model named the Geoscience (Earth Resources) Data Model 3.0 has been developed based on the conceptual design of NADM-C1.0 and EGDM 812. Such adaptation makes this data model interoperable with data models from other geoscience fields. The focus of current data model is to effectively manage multi datasets related with the study of earth resources and to create relationship among data types.
The conceptual data model for earth resources is successfully implemented physically by integrating a GIS and relational data storage. The direct link between relational database and GIS makes the database contents highly visual and spatially enabling. Database contents are fully georeferenced through different types of georeferencing systems that enables data integration, visualization and analysis of multi geoscience datasets in 2D and 3D environment. A new way of geologic analysis through visualization of virtually all kinds of geoscience datasets is proposed.
The earth resources research and industry can take benefits on this system through better data management and effective geologic visualization that in turn accelerate a better understanding of earth resources. Meanwhile wider geoscience community will benefit from better interaction and data sharing among geoscience fields for accelerating a better understanding of our complex earth. 相似文献
The conceptual data model for earth resources is successfully implemented physically by integrating a GIS and relational data storage. The direct link between relational database and GIS makes the database contents highly visual and spatially enabling. Database contents are fully georeferenced through different types of georeferencing systems that enables data integration, visualization and analysis of multi geoscience datasets in 2D and 3D environment. A new way of geologic analysis through visualization of virtually all kinds of geoscience datasets is proposed.
The earth resources research and industry can take benefits on this system through better data management and effective geologic visualization that in turn accelerate a better understanding of earth resources. Meanwhile wider geoscience community will benefit from better interaction and data sharing among geoscience fields for accelerating a better understanding of our complex earth. 相似文献