Lagrangian coherent structures in the California Current System – sensitivities and limitations     

Cheryl S. Harrison  Gary A. Glatzmaier 《地球物理与天体物理流体动力学》2013,107(1):22-44

We report on numerical experiments to test the sensitivity of Lagrangian coherent structures (LCSs), found by identifying ridges of the finite-time Lyapunov exponent (FTLE), to errors in two systems representing the California Current System (CCS). First, we consider a synthetic mesoscale eddy field generated from Fourier filtering satellite altimetry observations of the CCS. Second, we consider the full observational satellite altimetry field in the same region. LCS are found to be relatively insensitive to both sparse spatial and temporal resolution and to the velocity field interpolation method. Strongly attracting and repelling LCS are robust to perturbations of the velocity field of over 20% of the maximum regional velocity. Contours of the Okubo–Weiss (OW) parameter are found to be consistent with LCS in large mature eddies in the unperturbed systems. The OW parameter is unable to identify eddies at the uncertainty level expected for altimetry observations of the CCS. At this expected error level, the FTLE method is reliable for locating boundaries of large eddies and strong jets. Small LCS features such as lobes are not well resolved even at low error levels, suggesting that reliable determination of lobe dynamics from altimetry will be problematic.  相似文献   

Flow-through PSICAM: a new approach for determining water constituents absorption continuously   总被引：1，自引：0，他引：1  

Jochen Wollschläger  Maik Grunwald  Rüdiger Röttgers  Wilhelm Petersen 《Ocean Dynamics》2013,63(7):761-775

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Material Geographies and Postcolonialism   总被引：1，自引：0，他引：1  

Cheryl McEwan 《Singapore journal of tropical geography》2003,24(3):340-355

While postcolonial studies have inspired new ideas, a new language and a new theoretical inflection for a wide range of teaching and research in human geography, there have been few sustained discussions about what might constitute a postcolonial geography. This paper attempts to deal with this absence by exploring the possibilities of material geographies of postcolonialism. It suggests that geographers are particularly well placed to respond to criticisms of postcolonialism as remaining overwhelmingly textual, cultural and/or historical in focus by contributing towards a productive engagement between postcolonialism and the material realities of global inequalities, and towards a revivified political and ethical project. It explores how particular tactics might inform postcolonial methodologies within geography and makes some tentative suggestions on what a postcolonial political praxis might look like.  相似文献   

Wind tunnel measurement of boundary-layer response to sediment transport   总被引：3，自引：0，他引：3  

Cheryl McKenna Neuman  Marianne Maljaars 《Boundary-Layer Meteorology》1997,84(1):67-83

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Diets of short-tailed shearwaters in the southeastern Bering Sea     

George L. Hunt  Jr.  Cheryl Baduini  Jaime Jahncke 《Deep Sea Research Part II: Topical Studies in Oceanography》2002,49(26)

In the late 1990s, the southeastern Bering Sea exhibited a number of anomalous conditions, including a major die-off of short-tailed shearwaters (Puffinus tenuirostris), a trans-equatorial migrant that constitutes a major portion of the marine bird biomass in the southeastern Bering Sea. As part of a larger study of the ecological role of the inner or structural front over the southeastern Bering Sea shelf, in 1997–1999, we collected short-tailed shearwaters to determine diet composition. In spring 1997, we found that short-tailed shearwaters were consuming predominately the euphausiid Thysanoessa raschii, a diet expected on the basis of past studies. However, in subsequent years, short-tailed shearwater diets in spring contained increasingly larger proportions of fish, in particular, sandlance (Ammodytes hexapterus), as well as other species of euphausiids (T. inermis in 1999). In summer and fall collections, short-tailed shearwater diets were more varied than in spring, and included both fish (age-0 gadids, 21–35% by weight) and a wider variety of euphausiid species (T. inermis and T. spinifera). In summer and fall, crab zoea (August 1998) and copepods (August 1999) were eaten by shearwaters collected while feeding within the inner front. Diets in 1997–1999 were broader than those found in previous studies of short-tailed shearwaters over the inner shelf and Bristol Bay, which had documented diets composed almost solely of T. raschii. Our data are consistent with the hypothesis that euphausiids were less available to short-tailed shearwaters foraging over the middle and coastal domains of the southeastern Bering Sea in 1997–1999 than has previously been true. Our results are also consistent with hypothesis that the inner front can affect the availability of prey to shearwaters.  相似文献   

Application of a coupled discontinuous–continuous Galerkin finite element shallow water model to coastal ocean dynamics     

Cheryl Ann Blain  T. Christopher Massey 《Ocean Modelling》2005,10(3-4):283-315

A coupled discontinuous–continuous Galerkin (DG–CG) shallow water model is compared to a continuous Galerkin generalized wave-continuity equation (GWCE) based model for the coastal ocean, whereby local mass imbalance typical of GWCE-based solutions is eliminated using the coupled DG–CG approach. Two mass imbalance indicators for the GWCE-based model are presented and analyzed. The indicators motivate discussion on the suitability of using a GWCE-based model versus the locally conservative coupled DG–CG model. Both realistic and idealized test problems for tide, wind, and wave-driven circulation form the basis of the study. For the problems studied, coupled DG–CG solutions retain the robustness of well-documented solutions from GWCE-based models and also capture the dynamics driven by small-scale, highly advective processes which are problematic for GWCE-based models. Issues associated with the coupled DG–CG model are explored, including increased cost due to increased degrees of freedom, the necessary application of slope limiters, as well as the actual coupling process.  相似文献   

The Multifunctionality of Country Stores: Insights on Resilience from Rural Vermont          下载免费PDF全文

Cheryl Morse 《Geographical review》2018,108(3):457-475

A multifunctionality analysis of built environments within rural landscapes can deepen understanding of how contemporary rural places function. There is an urgent need for this knowledge as small towns in the United States lose socio‐economic infrastructure resulting from restructuring, demographic change, and the centralization of services. This qualitative and exploratory study of country stores in rural Vermont finds that stores operate as key socio‐spatial nodes within broader geographic networks. Analysis of the goods, functions, and services stores furnish reveals the reflexive relationships stores have with the physical and cultural geographies of their regions. In moments of community crisis and under certain conditions, stores exhibit hyper‐functionality. Built environments and their socio‐spatial roles in multifunctional landscapes should be included in analyses of rural community resilience.  相似文献   

Happy to Be Home: Place-Based Attachments,Family Ties,and Mobility among Rural Stayers     

Cheryl E. Morse  Jill Mudgett 《The Professional geographer》2018,70(2):261-269

Migration research has traditionally centered on tracing movement; however, the experience of staying in place has begun to capture scholarly attention. Drawing on data from an online residential decision-making survey, this article focuses specifically on the reasons that contented Vermonters cite for remaining in their home state. A statistical analysis of responses reveals the dominance of place-based factors and family ties in stayers' residential decision making. Contented stayers highly value landscape and community, as well as living near family. Biographical sketches of individual respondents show the emotional dimensions of choosing to stay, as well as the diverse forms of mobility that contented stayers exercise to remain happy at home. In its focus on stayers, this research situates itself within new geographic inquiries into place attachment and studies of “immobile” populations.  相似文献   

Aeolian sediment flux decay: Non-linear behaviour on developing deflation lag surfaces     

Cheryl Mckenna Neuman  W. G. Nickling 《地球表面变化过程与地形》1995,20(5):423-435

Wind tunnel simulations of the effect of non-erodible roughness elements on sediment transport show that the flux ratio q/q_s, shear velocity U*, and roughness density λ are co-dependent variables. Initially, the sediment flux is enhanced by kinetic energy retention in relatively elastic collisions that occur at the roughness element surfaces, but at the same time, the rising surface coverage of the immobile elements reduces the probability of grain ejection. A zone of strong shearing stress develops within 0·03 to 0·04 m of the rough bed because of a relative straightening of velocity profiles which are normally convex with saltation drag. This positive influence on fluid entrainment is opposed by declining shear stress partitioned to the sand bed. Similarly, because the free stream velocity U_f is fixed while U_* increases, velocity at height z and particle momentum gain from the airstream decline, leading eventually to lower numbers of particles ejected on average at each impact. When the ratio of the element basal area to frontal area σ is approximately equal to 3·5, secondary flow effects appear to become significant, so that the dimensionless aerodynamic roughness parameter Z₀/h and shear stress on the exposed sand bed T_s decrease. It is at this point that grain supply to the airstream and saltation drag appear to be significantly reduced, thereby intensifying the reduction in U_*. The zone of strong fluid shear near the bed dissipates.  相似文献   

Concubines and Power. Five Hundred Years in a Northern Nigerian Palace – Heidi J. Nast     

Cheryl McEwan 《Singapore journal of tropical geography》2006,27(2):228-229

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