Using a landform evolution model to study ephemeral gullying in agricultural fields: the effects of rainfall patterns on ephemeral gully dynamics          下载免费PDF全文

David Hoober  Tal Svoray  Sagy Cohen 《地球表面变化过程与地形》2017,42(8):1213-1226

Water driven soil erosion is a major cause of land degradation worldwide. Ephemeral gullies (EGs) are considered key contributors to agricultural catchment soil loss. Despite their importance, the parameters and drivers controlling EG dynamics have not been adequately quantified. Here we investigate the effects of rainfall characteristics on EGs, using the physically based landform evolution model (LEM) CAESAR‐Lisflood. An initial goal of this study was to test the feasibility of using a LEM to estimate EG dynamics based on an easily obtainable and moderate spatial resolution (2 × 2 m) Digital Elevation Model (DEM). EG evolution was simulated for two rainfall seasons in a 0.37 km² agricultural plot situated in a semiarid catchment in central Israel. The 2014 rainfall season was used to calibrate the model and the 2015 season was used for validation. The model overall well predicted the EG network structure and average depth but tended to underestimate the EG length. The effects of rainfall characteristics on EG dynamics were investigated by comparing simulations employing seven rainfall scenarios. Four of these scenarios differ in their overall rainfall volume relative to observed precipitation (+20%, +10%, ?10%, ?20%). The remaining three scenarios vary in the temporal distribution of rainfall during each storm, allowing us to isolate the effect of rainfall intensity on EG evolution. The results show that: (1) EG dynamics strongly correlated with changes in rainfall volume; (2) small‐scale morphological behavior varies between rainfall scenarios, resulting in different meandering and connectivity variability; (3) EG evolution is divided into two main stages, an initial rapid development occurring after the first two weeks of the rainy season, followed by a stable development period; (4) a 12 mm h^?1 intensity threshold was observed to initiate and, later, modify EGs; and (5) inner storm rainfall variability can have a considerable effect on EG evolution. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

On the interaction between a hurricane,the Gulf Stream and coastal sea level     

Tal Ezer 《Ocean Dynamics》2018,68(10):1259-1272

Tropical storms and hurricanes in the western North Atlantic Ocean can impact the US East Coast in several ways. Direct effects include storm surges, winds, waves, and precipitation and indirect effects include changes in ocean dynamics that consequently impact the coast. Hurricane Matthew [October, 2016] was chosen as a case study to demonstrate the interaction between an offshore storm, the Gulf Stream (GS) and coastal sea level. A regional numerical ocean model was used, to conduct sensitivity experiments with different surface forcing, using wind and heat flux data from an operational hurricane-ocean coupled forecast system. An additional experiment used the observed Florida Current (FC) transport during the hurricane as an inflow boundary condition. The experiments show that the hurricane caused a disruption in the GS flow that resulted in large spatial variations in temperatures with cooling of up to ~?4 °C by surface heat loss, but the interaction of the winds with the GS flow also caused some local warming near fronts and eddies (relative to simulations without a hurricane). A considerable weakening of the FC transport (~?30%) has been observed during the hurricane (a reduction of ~?10 Sv in 3 days; 1Sv?=?10⁶ m³ s^?1), so the impact of the FC was explored by the model. Unlike the abrupt and large wind-driven storm surge (up to 2 m water level change within 12 h in the South Atlantic Bight), the impact of the weakening GS on sea level is smaller but lasted for several days after the hurricane dissipated, as seen in both the model and altimeter data. These results can explain observations that show minor tidal flooding along long stretches of coasts for several days following passages of hurricanes. Further analysis showed the short-term impact of the hurricane winds on kinetic energy versus the long-term impact of the hurricane-induced mixing on potential energy, whereas several days are needed to reestablish the stratification and rebuild the strength of the GS to its pre-hurricane conditions. Understanding the interaction between storms, the Gulf Stream and coastal sea level can help to improve prediction of sea level rise and coastal flooding.  相似文献   

Editorial—the 7th International Workshop on Modeling the Ocean (IWMO 2015)     

Lie-Yauw Oey  Xiao Hua Wang  Tal Ezer  Yign Noh  Andrew McC. Hogg 《Ocean Dynamics》2017,67(12):1645-1647

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Physical reworking by near-bottom flow alters the metazoan meiofauna of Fieberling Guyot (northeast Pacific)     

David Thistle  Lisa A. Levin  Andrew J Gooday  Olaf Pfannkuche  P John D. Lambshead 《Deep Sea Research Part I: Oceanographic Research Papers》1999,46(12):185

Although much of the deep sea is physically tranquil, some regions experience near-bottom flows that rework the surficial sediment. During periods of physical reworking, animals in the reworked layer risk being suspended, which can have both positive and negative effects. Reworking can also change the sediment in ecologically important ways, so the fauna of reworked sites should differ from that of quiescent locations. We combined data from two reworked, bathyal sites on the summit of Fieberling Guyot (32°27.631′N, 127°49.489′W; 32°27.581′N, 127°47.839′W) and compared the results with those of more tranquil sites. We tested for differences in the following parameters, which seemed likely to be sensitive to the direct or indirect effects of reworking: (1) the vertical distribution of the meiofauna in the sea bed, (2) the relative abundance of surface-living harpacticoids, (3) the proportion of the fauna consisting of interstitial harpacticoids, (4) the ratio of harpacticoids to nematodes. We found that the vertical distributions of harpacticoid copepods, ostracods, and kinorhynchs were deeper on Fieberling. In addition, the relative abundance of surface-living harpacticoids was less, the proportion of interstitial harpacticoids was greater, and the ratio of harpacticoids to nematodes was greater on Fieberling. These differences between Fieberling and the comparison sites suggest that physical reworking affects deep-sea meiofauna and indicate the nature of some of the effects.  相似文献   

DAMÉE-NAB: the base experiments     

Eric P. Chassignet  Hernan Arango  David Dietrich  Tal Ezer  Michael Ghil  Dale B. Haidvogel  C. -C. Ma  Avichal Mehra  Afonso M. Paiva  Ziv Sirkes 《Dynamics of Atmospheres and Oceans》2000,32(3-4)

The results of an intercomparison experiment performed with five numerical ocean models of different architecture are presented. While all models are able to simulate the large-scale characteristics of the North Atlantic circulation with a fair degree of realism, they also exhibit differences that can be attributed to the choices made in vertical coordinates, domain size, and boundary conditions.  相似文献   

The influence of geological, geochemical, and biogenic habitat heterogeneity on seep biodiversity     

Erik E. Cordes  Marina R. Cunha  Joëlle Galéron  Camilo Mora  Karine Olu-Le Roy  Myriam Sibuet  Saskia Van Gaever  Ann Vanreusel  & Lisa A. Levin 《Marine Ecology》2010,31(1):51-65

Cold seeps are among the most heterogeneous of all continental margin habitats. Abiotic sources of heterogeneity in these systems include local variability in fluid flow, geochemistry, and substrate type, which give rise to different sets of microbial communities, microbial symbiont-bearing foundation species, and associated heterotrophic species. Biogenic habitats created by microbial mats and the symbiotic species including vesicomyid clams, bathymodiolin mussels, and siboglinid tubeworms add an additional layer of complexity to seep habitats. These forms of habitat heterogeneity result in a variety of macrofaunal and meiofaunal communities that respond to changes in structural complexity, habitat geochemistry, nutrient sources, and interspecific interactions in different ways and at different scales. These responses are predicted by a set of theoretical metacommunity models, the most appropriate of which for seep systems appears to be the 'species sorting' concept, an extension of niche theory. This concept is demonstrated through predictable patterns of community assembly, succession, and beta-level diversity. These processes are described using a newly developed analytical technique examining the change in the slope of the species accumulation curve with the number of habitats examined. The diversity response to heterogeneity has a consistent form, but quantitatively changes at different seep sites around the world as the types of habitats present and the size-classes of fauna analyzed change. The increase in beta diversity across seep habitat types demonstrates that cold seeps and associated biogenic habitats are significant sources of heterogeneity on continental margins globally.  相似文献   

Bringing stakeholders,scientists, and managers together through an integrated ecosystem assessment process     

Yvonne L. deReynier  Phillip S. Levin  Noriko L. Shoji 《Marine Policy》2010

For decades, the scientific community has conducted essential background research and developed appropriate modeling tools in support of an ecosystem-based approach to natural resource management. Resource managers and the public, however, lack a clear roadmap for working with scientists to move beyond the traditional single-species approach. With current management processes so strongly focused on working in a species-by-species framework, there are entrenched cultural and institutional challenges to shifting those processes toward ecosystem-based management. We propose using the integrated ecosystem assessment process to both develop new management ideas for a particular ecosystem, and to help shift public policy processes and perceptions to embrace ecosystem approaches to management.  相似文献   

Numerical modeling of the impact of hurricanes on ocean dynamics: sensitivity of the Gulf Stream response to storm’s track     

Ezer  Tal 《Ocean Dynamics》2019,69(9):1053-1066

Ocean Dynamics - The study is focused on the disruption that a storm can cause to ocean stratification and ocean currents in a region dominated by a western boundary current and meso-scale...  相似文献   

The Sunrise Mission     

P. Barthol  A. Gandorfer  S. K. Solanki  M. Sch��ssler  B. Chares  W. Curdt  W. Deutsch  A. Feller  D. Germerott  B. Grauf  K. Heerlein  J. Hirzberger  M. Kolleck  R. Meller  R. M��ller  T. L. Riethm��ller  G. Tomasch  M. Kn?lker  B. W. Lites  G. Card  D. Elmore  J. Fox  A. Lecinski  P. Nelson  R. Summers  A. Watt  V. Mart��nez?Pillet  J. A. Bonet  W. Schmidt  T. Berkefeld  A. M. Title  V. Domingo  J. L. Gasent?Blesa  J. C. del Toro?Iniesta  A. L��pez?Jim��nez  A. ��lvarez-Herrero  L. Sabau-Graziati  C. Widani  P. Haberler  K. H?rtel  D. Kampf  T. Levin  I. P��rez?Grande  A. Sanz-Andr��s  E. Schmidt 《Solar physics》2011,268(1):1-34

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Seismotectonics and Earth tides     

B. W. Levin  E. V. Sasorova 《Russian Journal of Pacific Geology》2012,6(1):70-77

The results of the processing and analysis of the global earthquake distribution (more than 250000 events based on the ISC catalog) and the study of moonquakes distribution (about 900 events based on the published materials) are presented. It was found that the number of events and the energy for both cases show a bimodal distribution with maximums in the middle latitudes, zero values at the polarcaps, and a local minimum in the vicinity of the equator. The probable influence of tectonic processes on the revealed character of the seismic event distribution is analyzed, and the role of Earth tides in the activation of the seismicity in the symmetric zones on both sides of the equator is shown.  相似文献