Journal articles: 'Topographic steering'

1

Marshall, David. "Topographic Steering of the Antarctic Circumpolar Current." Journal of Physical Oceanography 25, no. 7 (July 1995): 1636–50. http://dx.doi.org/10.1175/1520-0485(1995)025<1636:tsotac>2.0.co;2.

Full text

APA, Harvard, Vancouver, ISO, and other styles

2

Jones, B., S. Boudjelas, and E. G. Mitchelson-Jacob. "Topographic steering of winds in Vestfjorden, Norway." Weather 52, no. 10 (October 1997): 304–11. http://dx.doi.org/10.1002/j.1477-8696.1997.tb05526.x.

Full text

APA, Harvard, Vancouver, ISO, and other styles

3

Wåhlin, A. K. "Topographic steering of dense currents with application to submarine canyons." Deep Sea Research Part I: Oceanographic Research Papers 49, no. 2 (February 2002): 305–20. http://dx.doi.org/10.1016/s0967-0637(01)00058-9.

Full text

APA, Harvard, Vancouver, ISO, and other styles

4

Kuddannaya, Shreyas, Chong Swee Tong, Yantao Fan, and Yilei Zhang. "Geometrically Mediated Topographic Steering of Neurite Behaviors and Network Formation." Advanced Materials Interfaces 5, no. 7 (February 9, 2018): 1700819. http://dx.doi.org/10.1002/admi.201700819.

Full text

APA, Harvard, Vancouver, ISO, and other styles

5

Trodahl, Marta, and Pål Erik Isachsen. "Topographic Influence on Baroclinic Instability and the Mesoscale Eddy Field in the Northern North Atlantic Ocean and the Nordic Seas." Journal of Physical Oceanography 48, no. 11 (November 2018): 2593–607. http://dx.doi.org/10.1175/jpo-d-17-0220.1.

Full text

Abstract:

AbstractA weak planetary vorticity gradient and weak density stratification in the northern North Atlantic and Nordic seas lead to time-mean currents that are strongly guided by bottom topography. The topographic steering sets up distinct boundary currents with strong property fronts that are prone to both baroclinic and barotropic instability. These instability processes generate a macroturbulent eddy field that spreads buoyancy and other tracers out from the boundary currents and into the deep basins. In this paper we investigate the particular role played by baroclinic instability in generating the observed eddy field, comparing predictions from linear stability calculations with diagnostics from a nonlinear eddy-permitting ocean model hindcast. We also look into how the bottom topography impacts instability itself. The calculations suggest that baroclinic instability is a consistent source of the eddy field but that topographic potential vorticity gradients impact unstable growth significantly. We also observe systematic topographic effects on finite-amplitude eddy characteristics, including a general suppression of length scales over the continental slopes. Investigation of the vertical structure of unstable modes reveal that Eady theory, even when modified to account for a bottom slope, is unfit as a lowest-order model for the dynamics taking place in these ocean regions.

APA, Harvard, Vancouver, ISO, and other styles

6

Kessler, Mark A., Robert S. Anderson, and Jason P. Briner. "Fjord insertion into continental margins driven by topographic steering of ice." Nature Geoscience 1, no. 6 (May 11, 2008): 365–69. http://dx.doi.org/10.1038/ngeo201.

Full text

APA, Harvard, Vancouver, ISO, and other styles

7

Wakes, Sarah J., Michael J. Hilton, and Teresa Konlechner. "Topographic Steering of Oblique Incident Winds Across a Foredune-Parabolic Topography, Mason Bay, Stewart Island, New Zealand." Journal of Coastal Research 75, sp1 (March 3, 2016): 343–47. http://dx.doi.org/10.2112/si75-069.1.

Full text

APA, Harvard, Vancouver, ISO, and other styles

8

Smith, Alex, Derek W. T. Jackson, J. Andrew G. Cooper, Meiring Beyers, and Colin Breen. "Whole-island wind bifurcation and localized topographic steering: Impacts on aeolian dune dynamics." Science of The Total Environment 763 (April 2021): 144444. http://dx.doi.org/10.1016/j.scitotenv.2020.144444.

Full text

APA, Harvard, Vancouver, ISO, and other styles

9

Darelius, E. "Topographic steering of dense overflows: Laboratory experiments with V-shaped ridges and canyons." Deep Sea Research Part I: Oceanographic Research Papers 55, no. 8 (August 2008): 1021–34. http://dx.doi.org/10.1016/j.dsr.2008.04.008.

Full text

APA, Harvard, Vancouver, ISO, and other styles

10

Winter, Kate, Neil Ross, Fausto Ferraccioli, Tom A. Jordan, Hugh F. J. Corr, René Forsberg, Kenichi Matsuoka, Arne V. Olesen, and Tania G. Casal. "Topographic Steering of Enhanced Ice Flow at the Bottleneck Between East and West Antarctica." Geophysical Research Letters 45, no. 10 (May 17, 2018): 4899–907. http://dx.doi.org/10.1029/2018gl077504.

Full text

APA, Harvard, Vancouver, ISO, and other styles

11

Moor, J. J. W. de, R. T. van Balen, and C. Kasse. "Simulating meander evolution of the Geul River (the Netherlands) using a topographic steering model." Earth Surface Processes and Landforms 32, no. 7 (2007): 1077–93. http://dx.doi.org/10.1002/esp.1466.

Full text

APA, Harvard, Vancouver, ISO, and other styles

12

Broomé, Sara, and Johan Nilsson. "Stationary Sea Surface Height Anomalies in Cyclonic Boundary Currents: Conservation of Potential Vorticity and Deviations from Strict Topographic Steering." Journal of Physical Oceanography 46, no. 8 (August 2016): 2437–56. http://dx.doi.org/10.1175/jpo-d-15-0219.1.

Full text

Abstract:

AbstractIn high-latitude subpolar seas, such as the Nordic seas and the Labrador Sea, time-mean geostrophic currents mediate the bulk of the meridional oceanic heat transport. These currents are primarily encountered along the continental slopes as intense cyclonic boundary currents, which, because of the relatively weak stratification, should be strongly steered by the bottom topography. However, analyses of hydrographic and satellite altimetric data along depth contours in Nordic seas boundary currents reveal some remarkable, stationary, along-stream variations in the depth-integrated buoyancy and bottom pressure. A closer examination shows that these variations are linked to changes in steepness and curvature of the continental slope. To examine the underlying dynamics, a steady-state model of a cyclonic stratified boundary current over a topographic slope is developed in the limit of small Rossby numbers. Based on potential vorticity conservation, equations for the zeroth- and first-order pressure and buoyancy fields are derived. To the lowest order, the flow is completely aligned with the bottom topography. However, the first-order results show that where the lowest-order flow increases (decreases) its relative vorticity along a depth contour, the first-order pressure and depth-integrated buoyancy increase (decrease). This response is associated with cross-isobath flows, which induce stretching/compression of fluid elements that compensates for the changes in relative vorticity. The model-predicted along-isobath variations in pressure and depth-integrated buoyancy are comparable in magnitude to the ones found in the observational data from the Nordics Seas.

APA, Harvard, Vancouver, ISO, and other styles

13

Walker, Ian J., Patrick A. Hesp, Robin G. D. Davidson-Arnott, and Jeff Ollerhead. "Topographic Steering of Alongshore Airflow over a Vegetated Foredune: Greenwich Dunes, Prince Edward Island, Canada." Journal of Coastal Research 225 (September 2006): 1278–91. http://dx.doi.org/10.2112/06a-0010.1.

Full text

APA, Harvard, Vancouver, ISO, and other styles

14

Jiang, Lin, and Roland W. Garwood. "Effects of topographic steering and ambient stratification on overflows on continental slopes: A model study." Journal of Geophysical Research: Oceans 103, no. C3 (March 15, 1998): 5459–76. http://dx.doi.org/10.1029/97jc03201.

Full text

APA, Harvard, Vancouver, ISO, and other styles

15

Gille, Sarah T. "Float Observations of the Southern Ocean. Part I: Estimating Mean Fields, Bottom Velocities, and Topographic Steering." Journal of Physical Oceanography 33, no. 6 (June 2003): 1167–81. http://dx.doi.org/10.1175/1520-0485(2003)033<1167:footso>2.0.co;2.

Full text

APA, Harvard, Vancouver, ISO, and other styles

16

Yang, Ming-Jen, Da-Lin Zhang, and Hsiao-Ling Huang. "A Modeling Study of Typhoon Nari (2001) at Landfall. Part I: Topographic Effects." Journal of the Atmospheric Sciences 65, no. 10 (October 2008): 3095–115. http://dx.doi.org/10.1175/2008jas2453.1.

Full text

Abstract:

Although there have been many observational and modeling studies of tropical cyclones, understanding of their intensity and structural changes after landfall is rather limited. In this study, several 84-h cloud-resolving simulations of Typhoon Nari (2001), a typhoon that produced torrential rainfall of more than 1400 mm over Taiwan, are carried out using a quadruply nested–grid mesoscale model whose finest grid size was 2 km. It is shown that the model reproduces reasonably well Nari’s kinematic and precipitation features as well as structural changes, as verified against radar and rain gauge observations. These include the storm track, the contraction and sizes of the eye and eyewall, the spiral rainbands, the rapid pressure rise (∼1.67 hPa h−1) during landfall, and the nearly constant intensity after landfall. In addition, the model captures the horizontal rainfall distribution and some local rainfall maxima associated with Taiwan’s orography. A series of sensitivity experiments are performed in which Taiwan’s topography is reduced to examine the topographic effects on Nari’s track, intensity, rainfall distribution, and amount. Results show that the impact of island terrain on Nari’s intensity is nearly linear, with stronger storm intensity but less rainfall in lower-terrain runs. In contrast, changing the terrain heights produces nonlinear tracks with circular shapes and variable movements associated with different degrees of blocking effects. Parameter and diagnostic analyses reveal that the nonlinear track dependence on terrain heights results from the complex interactions between the environmental steering flow, Nari’s intensity, and Taiwan’s topography, whereas the terrain-induced damping effects balance the intensifying effects of latent heat release associated with the torrential rainfall in maintaining the near-constant storm intensity after landfall.

APA, Harvard, Vancouver, ISO, and other styles

17

Belmadani, Ali, Emilio Concha, David Donoso, Alexis Chaigneau, François Colas, Nikolai Maximenko, and Emanuele Di Lorenzo. "Striations and preferred eddy tracks triggered by topographic steering of the background flow in the eastern South Pacific." Journal of Geophysical Research: Oceans 122, no. 4 (April 2017): 2847–70. http://dx.doi.org/10.1002/2016jc012348.

Full text

APA, Harvard, Vancouver, ISO, and other styles

18

Huang, Ching-Yuang, Cher-Wei Chou, Shu-Hua Chen, and Jia-Hong Xie. "Topographic Rainfall of Tropical Cyclones past a Mountain Range as Categorized by Idealized Simulations." Weather and Forecasting 35, no. 1 (December 31, 2019): 25–49. http://dx.doi.org/10.1175/waf-d-19-0120.1.

Full text

Abstract:

Abstract Topographic rainfall induced by westbound tropical cyclones past an island mountain is investigated using an idealized Weather Research and Forecasting (WRF) Model. Idealized simulations with varying vortex core size R (100–250 km), vortex intensity Vmax (20–35 m s−1), and steering wind speed U (4–10 m s−1) are conducted. The results show that the geometric distributions of major rainfall over the island are not greatly sensitive to cloud microphysics schemes using either single momentum or double momentum. Major rainfall is produced over northeastern and southwestern slopes of the mountain for smaller U. As U is doubled, the rainfall, however, is considerably weakened or is present only over southwestern slopes. For smaller U, a bifurcation of island rainfall with a sudden change in intensity or geometric shifting exists within a tiny range of R or Vmax. When the bifurcation occurs with small track deviations, geometric distributions of major rainfall are also more sensitive to cloud microphysics schemes. Such formation of bifurcation or double-peak rainfall, however, is significantly reduced when the terrain size is doubled. Systematic experiments are conducted to relate the topographical rainfalls over the northern half, southern half, and the whole of the mountain slopes to varying R, Vmax, and U. Larger U tends to produce much larger southern rainfall than northern rainfall. The average and maximum rainfalls generally increase with increased Vmax, except for large R. The decrease of average rainfall and maximum rainfall with increased U is more evident for smaller R, while not necessarily true for larger R.

APA, Harvard, Vancouver, ISO, and other styles

19

Liang, M., V. R. Voller, and C. Paola. "A reduced-complexity model for river delta formation – Part 1: Modeling deltas with channel dynamics." Earth Surface Dynamics 3, no. 1 (January 28, 2015): 67–86. http://dx.doi.org/10.5194/esurf-3-67-2015.

Full text

Abstract:

Abstract. In this work we develop a reduced-complexity model (RCM) for river delta formation (referred to as DeltaRCM in the following). It is a rule-based cellular morphodynamic model, in contrast to reductionist models based on detailed computational fluid dynamics. The basic framework of this model (DeltaRCM) consists of stochastic parcel-based cellular routing schemes for water and sediment and a set of phenomenological rules for sediment deposition and erosion. The outputs of the model include a depth-averaged flow field, water surface elevation and bed topography that evolve in time. Results show that DeltaRCM is able (1) to resolve a wide range of channel dynamics – including elongation, bifurcation, avulsion and migration – and (2) to produce a variety of deltas such as alluvial fan deltas and deltas with multiple orders of bifurcations. We also demonstrate a simple stratigraphy recording component which tracks the distribution of coarse and fine materials and the age of the deposits. Essential processes that must be included in reduced-complexity delta models include a depth-averaged flow field that guides sediment transport a nontrivial water surface profile that accounts for backwater effects at least in the main channels, both bedload and suspended sediment transport, and topographic steering of sediment transport.

APA, Harvard, Vancouver, ISO, and other styles

20

Stevens, D. P., and S. R. Thompson. "The South Atlantic in the Fine-Resolution Antarctic Model." Annales Geophysicae 12, no. 9 (August 31, 1994): 826–39. http://dx.doi.org/10.1007/s00585-994-0826-5.

Full text

Abstract:

Abstract. The geographical area covered by the Fine-Resolution Antarctic Model (FRAM) includes that part of the South Atlantic south of 24°S. A description of the dynamics and thermodynamics of this region of the model is presented. Both the mean and eddy fields in the model are in good agreement with reality, although the magnitude of the transients is somewhat reduced. The heat flux is northward and in broad agreement with many other estimates. Agulhas eddies are formed by the model and propagate westward into the Atlantic providing a mechanism for fluxing heat from the Indian Ocean. The confluence of the Brazil and Falkland currents produces a strong front and a large amount of mesoscale activity. In the less stratified regions to the south, topographic steering of the Antarctic circumpolar current is important.

APA, Harvard, Vancouver, ISO, and other styles

21

Thompson, Andrew F., and Jean-Baptiste Sallée. "Jets and Topography: Jet Transitions and the Impact on Transport in the Antarctic Circumpolar Current." Journal of Physical Oceanography 42, no. 6 (June 1, 2012): 956–72. http://dx.doi.org/10.1175/jpo-d-11-0135.1.

Full text

Abstract:

Abstract The Southern Ocean’s Antarctic Circumpolar Current (ACC) naturally lends itself to interpretations using a zonally averaged framework. Yet, navigation around steep and complicated bathymetric obstacles suggests that local dynamics may be far removed from those described by zonally symmetric models. In this study, both observational and numerical results indicate that zonal asymmetries, in the form of topography, impact global flow structure and transport properties. The conclusions are based on a suite of more than 1.5 million virtual drifter trajectories advected using a satellite altimetry–derived surface velocity field spanning 17 years. The focus is on sites of “cross front” transport as defined by movement across selected sea surface height contours that correspond to jets along most of the ACC. Cross-front exchange is localized in the lee of bathymetric features with more than 75% of crossing events occurring in regions corresponding to only 20% of the ACC’s zonal extent. These observations motivate a series of numerical experiments using a two-layer quasigeostrophic model with simple, zonally asymmetric topography, which often produces transitions in the front structure along the channel. Significantly, regimes occur where the equilibrated number of coherent jets is a function of longitude and transport barriers are not periodic. Jet reorganization is carried out by eddy flux divergences acting to both accelerate and decelerate the mean flow of the jets. Eddy kinetic energy is amplified downstream of topography due to increased baroclinicity related to topographic steering. The combination of high eddy kinetic energy and recirculation features enhances particle exchange. These results stress the complications in developing consistent circumpolar definitions of the ACC fronts.

APA, Harvard, Vancouver, ISO, and other styles

22

Mazzini, A., A. Akhmetzhanov, X. Monteys, and M. Ivanov. "The Porcupine Bank Canyon coral mounds: oceanographic and topographic steering of deep-water carbonate mound development and associated phosphatic deposition." Geo-Marine Letters 32, no. 3 (October 27, 2011): 205–25. http://dx.doi.org/10.1007/s00367-011-0257-8.

Full text

APA, Harvard, Vancouver, ISO, and other styles

23

Huang, Yi-Hsuan, Chun-Chieh Wu, and Yuqing Wang. "The Influence of Island Topography on Typhoon Track Deflection." Monthly Weather Review 139, no. 6 (June 1, 2011): 1708–27. http://dx.doi.org/10.1175/2011mwr3560.1.

Full text

Abstract:

Abstract High-resolution simulations for Typhoon Krosa (2007) and a set of idealized experiments are conducted using a full-physics model to investigate the eminent deflection of typhoon track prior to its landfall over mountainous island topography. The terrain height of Taiwan plays the most important role in Typhoon Krosa’s looping motion at its landfall, while the surface properties, details in the topographic shape of Taiwan, and the cloud microphysics are shown to be secondary to the track deflection. A simulation with 3-km resolution and realistic model settings reproduces the observed Krosa’s track, while that with 9-km resolution fails, suggesting that high resolution to better resolve the typhoon–terrain interactions is important for the prediction and simulation of typhoon track deflection prior to landfall. Results from idealized experiments with model configurations mimicking those of Supertyphoon Krosa show that vortices approaching the northern and central topography are significantly deflected to the south before making sharp turns to the north, forming a kinked track pattern prior to and during landfall. This storm movement is consistent with the observed looping cases in Taiwan. Both real-case and idealized simulations show strong channel winds enhanced between the storm and the terrain when deflection occurs. Backward trajectory analyses support the concept of the channeling effect, which has been previously found to be crucial to the looping motion of Typhoon Haitang (2005) as well. However, the inner-core asymmetric ventilation flow does not match the movement of a deflected typhoon perfectly, partly because the steering flow is not well defined and could not completely capture the terrain-induced deflection in the simulation and in nature.

APA, Harvard, Vancouver, ISO, and other styles

24

Carter, Glenn S., Michael C. Gregg, and Mark A. Merrifield. "Flow and Mixing around a Small Seamount on Kaena Ridge, Hawaii." Journal of Physical Oceanography 36, no. 6 (June 1, 2006): 1036–52. http://dx.doi.org/10.1175/jpo2924.1.

Full text

Abstract:

Abstract Microstructure observations over a small seamount on the Kaena Ridge, Hawaii, showed asymmetry in the along- and across-ridge directions. The ∼400-m-high seamount is on the southern edge of the ridge (centered at 21°43′49″N, 158°38′48″W), 42 km northwest of Oahu. A 1-km-resolution numerical simulation shows that the flow within the depth range of the seamount tends to be accelerated around the seamount rather than going up and over it. The flow patterns, however, are more complicated than for an isolated seamount because of the influence of the ∼3000-m-high Kaena Ridge. Comparison with the numerical simulations indicates that the across-ridge asymmetry, in which dissipation on the north-northeastern side of the seamount was higher and more concentrated toward the bed than on the south-southwestern side, is consistent with an M2 tidal beam generated at the northern edge of the ridge. The along-ridge asymmetry, with higher dissipation on the east-southeastern flank than on the west-northwestern flank, is in qualitative agreement with M2 shear variance from the model simulation. The average observed dissipation rate over the seamount was ɛ = 6.2 × 10−8 W kg−1, and diapycnal diffusivity was Kρ = 1.3 × 10−3 m2 s−1. Dissipation measurements following the 1000-m isobath south-southwest of the seamount suggest along-ridge internal tide generation caused by topographic steering that creates an along-ridge current over critical topography northwest of the seamount.

APA, Harvard, Vancouver, ISO, and other styles

25

Tamsitt, Veronica, Lynne D. Talley, Matthew R. Mazloff, and Ivana Cerovečki. "Zonal Variations in the Southern Ocean Heat Budget." Journal of Climate 29, no. 18 (August 26, 2016): 6563–79. http://dx.doi.org/10.1175/jcli-d-15-0630.1.

Full text

Abstract:

Abstract The spatial structure of the upper ocean heat budget in the Antarctic Circumpolar Current (ACC) is investigated using the ⅙°, data-assimilating Southern Ocean State Estimate (SOSE) for 2005–10. The ACC circumpolar integrated budget shows that 0.27 PW of ocean heat gain from the atmosphere and 0.38 PW heat gain from divergence of geostrophic heat transport are balanced by −0.58 PW cooling by divergence of Ekman heat transport and −0.09 PW divergence of vertical heat transport. However, this circumpolar integrated balance obscures important zonal variations in the heat budget. The air–sea heat flux shows a zonally asymmetric pattern of ocean heat gain in the Indian and Atlantic sectors and ocean heat loss in the Pacific sector of the ACC. In the Atlantic and Indian sectors of the ACC, the surface ocean heat gain is primarily balanced by divergence of equatorward Ekman heat transport that cools the upper ocean. In the Pacific sector, surface ocean heat loss and cooling due to divergence of Ekman heat transport are balanced by warming due to divergence of geostrophic heat advection, which is similar to the dominant heat balance in the subtropical Agulhas Return Current. The divergence of horizontal and vertical eddy advection of heat is important for warming the upper ocean close to major topographic features, while the divergence of mean vertical heat advection is a weak cooling term. The results herein show that topographic steering and zonal asymmetry in air–sea exchange lead to substantial zonal asymmetries in the heat budget, which is important for understanding the upper cell of the overturning circulation.

APA, Harvard, Vancouver, ISO, and other styles

26

Wang, Qiang, Claudia Wekerle, Sergey Danilov, Xuezhu Wang, and Thomas Jung. "A 4.5 km resolution Arctic Ocean simulation with the global multi-resolution model FESOM 1.4." Geoscientific Model Development 11, no. 4 (April 3, 2018): 1229–55. http://dx.doi.org/10.5194/gmd-11-1229-2018.

Full text

Abstract:

Abstract. In the framework of developing a global modeling system which can facilitate modeling studies on Arctic Ocean and high- to midlatitude linkage, we evaluate the Arctic Ocean simulated by the multi-resolution Finite Element Sea ice-Ocean Model (FESOM). To explore the value of using high horizontal resolution for Arctic Ocean modeling, we use two global meshes differing in the horizontal resolution only in the Arctic Ocean (24 km vs. 4.5 km). The high resolution significantly improves the model's representation of the Arctic Ocean. The most pronounced improvement is in the Arctic intermediate layer, in terms of both Atlantic Water (AW) mean state and variability. The deepening and thickening bias of the AW layer, a common issue found in coarse-resolution simulations, is significantly alleviated by using higher resolution. The topographic steering of the AW is stronger and the seasonal and interannual temperature variability along the ocean bottom topography is enhanced in the high-resolution simulation. The high resolution also improves the ocean surface circulation, mainly through a better representation of the narrow straits in the Canadian Arctic Archipelago (CAA). The representation of CAA throughflow not only influences the release of water masses through the other gateways but also the circulation pathways inside the Arctic Ocean. However, the mean state and variability of Arctic freshwater content and the variability of freshwater transport through the Arctic gateways appear not to be very sensitive to the increase in resolution employed here. By highlighting the issues that are independent of model resolution, we address that other efforts including the improvement of parameterizations are still required.

APA, Harvard, Vancouver, ISO, and other styles

27

Hendricks, Eric A., Yi Jin, Jonathan R. Moskaitis, James D. Doyle, Melinda S. Peng, Chun-Chieh Wu, and Hung-Chi Kuo. "Numerical Simulations of Typhoon Morakot (2009) Using a Multiply Nested Tropical Cyclone Prediction Model." Weather and Forecasting 31, no. 2 (April 1, 2016): 627–45. http://dx.doi.org/10.1175/waf-d-15-0016.1.

Full text

Abstract:

Abstract High-impact Typhoon Morakot (2009) was investigated using a multiply nested regional tropical cyclone prediction model. In the numerical simulations, the horizontal grid spacing, cumulus parameterizations, and microphysical parameterizations were varied, and the sensitivity of the track, intensity, and quantitative precipitation forecasts (QPFs) was examined. With regard to horizontal grid spacing, it is found that convective-permitting (5 km) resolution is necessary for a reasonably accurate QPF, while little benefit is gained through the use of a fourth domain at 1.67-km horizontal resolution. Significant sensitivity of the track forecast was found to the cumulus parameterization, which impacted the model QPFs. In particular, the simplified Arakawa–Schubert parameterization tended to erroneously regenerate the remnants of Tropical Storm Goni to the southwest of Morakot, affecting the large-scale steering flow and the track of Morakot. Strong sensitivity of the QPFs to the microphysical parameterization was found, with the track and intensity showing little sensitivity. It is also found that Morakot’s accumulated precipitation was reasonably predictable, with the control simulation producing an equitable threat score of 0.56 for the 3-day accumulated precipitation using a threshold of 500 mm. This high predictability of precipitation is due in part to more predictable large-scale and topographic forcing.

APA, Harvard, Vancouver, ISO, and other styles

28

Neelin, J. David, Baird Langenbrunner, Joyce E. Meyerson, Alex Hall, and Neil Berg. "California Winter Precipitation Change under Global Warming in the Coupled Model Intercomparison Project Phase 5 Ensemble." Journal of Climate 26, no. 17 (August 23, 2013): 6238–56. http://dx.doi.org/10.1175/jcli-d-12-00514.1.

Full text

Abstract:

Abstract Projections of possible precipitation change in California under global warming have been subject to considerable uncertainty because California lies between the region anticipated to undergo increases in precipitation at mid-to-high latitudes and regions of anticipated decrease in the subtropics. Evaluation of the large-scale model experiments for phase 5 of the Coupled Model Intercomparison Project (CMIP5) suggests a greater degree of agreement on the sign of the winter (December–February) precipitation change than in the previous such intercomparison, indicating a greater portion of California falling within the increased precipitation zone. While the resolution of global models should not be relied on for accurate depiction of topographic rainfall distribution within California, the precipitation changes depend substantially on large-scale shifts in the storm tracks arriving at the coast. Significant precipitation increases in the region arriving at the California coast are associated with an eastward extension of the region of strong Pacific jet stream, which appears to be a robust feature of the large-scale simulated changes. This suggests that effects of this jet extension in steering storm tracks toward the California coast constitute an important factor that should be assessed for impacts on incoming storm properties for high-resolution regional model assessments.

APA, Harvard, Vancouver, ISO, and other styles

29

Pedlosky, Joseph. "Baroclinic Flow around Planetary Islands in a Double Gyre: A Mechanism for Cross-Gyre Flow." Journal of Physical Oceanography 40, no. 5 (May 1, 2010): 1075–86. http://dx.doi.org/10.1175/2009jpo4375.1.

Full text

Abstract:

Abstract A quasigeostrophic, two-layer model is used to study the baroclinic circulation around a thin, meridionally elongated island. The flow is driven by either buoyancy forcing or wind stress, each of whose structure would produce an antisymmetric double-gyre flow. The ocean bottom is flat. When the island partially straddles the intergyre boundary, fluid from one gyre is forced to flow into the other. The amount of the intergyre flow depends on the island constant, that is, the value of the geostrophic streamfunction on the island in each layer. That constant is calculated in a manner similar to earlier studies and is determined by the average, along the meridional length of the island, of the interior Sverdrup solution just to the east of the island. Explicit solutions are given for both buoyancy and wind-driven flows. The presence of an island of nonzero width requires the determination of the baroclinic streamfunction on the basin’s eastern boundary. The value of the boundary term is proportional to the island’s area. This adds a generally small additional baroclinic intergyre flow. In all cases, the intergyre flow produced by the island is not related to topographic steering of the flow but rather the pressure anomaly on the island as manifested by the barotropic and baroclinic island constants. The vertical structure of the flow around the island is a function of the parameterization of the vertical mixing in the problem and, in particular, the degree to which long baroclinic Rossby waves can traverse the basin before becoming thermally damped.

APA, Harvard, Vancouver, ISO, and other styles

30

England, Matthew H., and Véronique C. Garçon. "South Atlantic circulation in a world ocean model." Annales Geophysicae 12, no. 9 (August 31, 1994): 812–25. http://dx.doi.org/10.1007/s00585-994-0812-y.

Full text

Abstract:

Abstract. The circulation in the South Atlantic Ocean has been simulated within a global ocean general circulation model. Preliminary analysis of the modelled ocean circulation in the region indicates a rather close agreement of the simulated upper ocean flows with conventional notions of the large-scale geostrophic currents in the region. The modelled South Atlantic Ocean witnesses the return flow and export of North Atlantic Deep Water (NADW) at its northern boundary, the inflow of a rather barotropic Antarctic Circumpolar Current (ACC) through the Drake Passage, and the inflow of warm saline Agulhas water around the Cape of Good Hope. The Agulhas leakage amounts to 8.7 Sv, within recent estimates of the mass transport shed westward at the Agulhas retroflection. Topographic steering of the ACC dominates the structure of flow in the circumpolar ocean. The Benguela Current is seen to be fed by a mixture of saline Indian Ocean water (originating from the Agulhas Current) and fresher Subantarctic surface water (originating in the ACC). The Benguela Current is seen to modify its flow and fate with depth; near the surface it flows north-westwards bifurcating most of its transport northward into the North Atlantic Ocean (for ultimate replacement of North Atlantic surface waters lost to the NADW conveyor). Deeper in the water column, more of the Benguela Current is destined to return with the Brazil Current, though northward flows are still generated where the Benguela Current extension encounters the coast of South America. At intermediate levels, these northward currents trace the flow of Antarctic Intermediate Water (AAIW) equatorward, though even more AAIW is seen to recirculate poleward in the subtropical gyre. In spite of the model's rather coarse resolution, some subtle features of the Brazil-Malvinas Confluence are simulated rather well, including the latitude at which the two currents meet. Conceptual diagrams of the recirculation and interocean exchange of thermocline, intermediate and deep waters are constructed from an analysis of flows bound between isothermal and isobaric surfaces. This analysis shows how the return path of NADW is partitioned between a cold water route through the Drake Passage (6.5 Sv), a warm water route involving the Agulhas Current sheeding thermocline water westward (2.5 Sv), and a recirculation of intermediate water originating in the Indian Ocean (1.6 Sv).

APA, Harvard, Vancouver, ISO, and other styles

31

Benyeogor, Mbadiwe S., Oladayo O. Olakanmi, and Sushant Kumar. "Design of Quad-Wheeled Robot for Multi-Terrain Navigation." Scientific Review, no. 62 (February 5, 2020): 14–22. http://dx.doi.org/10.32861/sr.62.14.22.

Full text

Abstract:

Wheeled robots are often utilized for various remote sensing and telerobotic applications because of their ability to navigate through dynamic environments, mostly under the partial control of a human operator. To make these robots capable to traverse through terrains of rough and uneven topography, their driving mechanisms and controllers must be very efficient at producing and controlling large mechanical power with great precision in real-time, however small the robot may be. This paper discusses an approach for designing a quad-wheeled robot, which is wirelessly controlled with a personal computer (PC) by medium-range radio frequency (RF) transceiver, to navigate through unpaved paths with little or no difficulty. An efficient servo-controlled Ackerman steering mechanism and a high-torque driving power-train were developed. The robot’s controller is programmed to receive and respond to RF control signals from the PC to perform the desired motions. The dynamics of the robot’s drivetrain is modeled and analyzed on MATLAB to predict its performances. The robot was tested on various topographies to determine its physical capabilities. Results show that the robot is capable of non-holonomically constrained motions on rough and uneven terrains.

APA, Harvard, Vancouver, ISO, and other styles

32

Li, Wenhao, and Feng Kang. "Design and Analysis of Steering and Lifting Mechanisms for Forestry Vehicle Chassis." Mathematical Problems in Engineering 2020 (March 12, 2020): 1–16. http://dx.doi.org/10.1155/2020/5971746.

Full text

Abstract:

Due to its special topographical structure, the forest working environment requires a vehicle chassis that can adapt well to complex terrain conditions. This article describes the key components of a chassis that was designed to adapt to complex terrain. The working principle and structural design of the steering structure and the lifting structure are analyzed in detail, and function verification is carried out. The steering mechanism has three degrees of freedom, and the first degree of freedom reduces the body’s inclination by 30°. The second degree of freedom can increase the steering angle of the chassis to 47°, decreasing the turning radius of the chassis. The third degree of freedom reduces the body rollover inclination by 30°. The entire steering mechanism enhances the ride and stability of the chassis. With the lifting mechanism, the wheel-legs are lifted so that the chassis can pass a limit height of 187 mm, and the wheel-legs are lowered to raise the center of gravity of the vehicle chassis by 244 mm. The entire lifting mechanism greatly improves the vehicle's ability to cross forest terrain. The size is reduced by 10% compared to other structures, and the lifting height and obstacle resistance are improved by 12.7%.

APA, Harvard, Vancouver, ISO, and other styles

33

Gratton, Eric, Mbadiwe Benyeogor, Kosisochukwu Nnoli, Oladayo Olakanmi, Liam Wolf, Zavier Berti, Sushant Kumar, and Piyal Saha. "Multi-terrain Quadrupedal-wheeled Robot Mechanism: Design, Modeling, and Analysis." European Journal of Engineering Research and Science 5, no. 12 (December 10, 2020): 24–33. http://dx.doi.org/10.24018/ejers.2020.5.12.2256.

Full text

Abstract:

For a robot to navigate in terrains of rough and uneven topographies, its drives and controllers must generate and control large mechanical power with great precision. This paper is aimed at developing an autonomous robot with active-suspensions in form of a hybrid quadrupedal-wheel drive mechanism. This involves a computational approach to optimizing the development cost without compromising the system’s performance. Using the Solidworks CAD tool, auxiliary components were designed and integrated with the bed structure to form an actively suspended robot drive mechanism. Also, using the S-Math Computing tool, the robot’s suspension system was optimized, employing a four-bar mechanism. To enhance the compatibility of this design with the intended controller, some mathematical equations and numerical validations were formulated and solved. These included the modeling of tip-over stability and skid steering, the trendline equations for computing the angular positions of the suspension servomotors, and the computation of R2– values for determining the accuracy of these trendline equations. Using finite element analysis (FEA), we simulated the structural integrity of key sub-components of the final structure. The results show that our mechanical design is appropriate for developing an actively suspended robot that can efficiently navigate in different terrestrial sites and topographies.

APA, Harvard, Vancouver, ISO, and other styles

34

Våge, Kjetil, Robert S. Pickart, G. W. K. Moore, and Mads Hvid Ribergaard. "Winter Mixed Layer Development in the Central Irminger Sea: The Effect of Strong, Intermittent Wind Events." Journal of Physical Oceanography 38, no. 3 (March 1, 2008): 541–65. http://dx.doi.org/10.1175/2007jpo3678.1.

Full text

Abstract:

Abstract The impact of the Greenland tip jet on the wintertime mixed layer of the southwest Irminger Sea is investigated using in situ moored profiler data and a variety of atmospheric datasets. The mixed layer was observed to reach 400 m in the spring of 2003 and 300 m in the spring of 2004. Both of these winters were mild and characterized by a low North Atlantic Oscillation (NAO) index. A typical tip jet event is associated with a low pressure system that is advected by upper-level steering currents into the region east of Cape Farewell and interacts with the high topography of southern Greenland. Heat flux time series for the mooring site were constructed that include the enhancing influence of the tip jet events. This was used to force a one-dimensional mixed layer model, which was able to reproduce the observed envelope of mixed layer deepening in both winters. The deeper mixed layer of the first winter was largely due to a higher number of robust tip jet events, which in turn was caused by the steering currents focusing more storms adjacent to southern Greenland. Application of the mixed layer model to the winter of 1994–95, a period characterized by a high-NAO index, resulted in convection exceeding 1700 m. This prediction is consistent with hydrographic data collected in summer 1995, supporting the notion that deep convection can occur in the Irminger Sea during strong winters.

APA, Harvard, Vancouver, ISO, and other styles

35

Tang, Chi Kit, and Johnny C. L. Chan. "Idealized simulations of the effect of Taiwan topography on the tracks of tropical cyclones with different steering flow strengths." Quarterly Journal of the Royal Meteorological Society 142, no. 701 (October 2016): 3211–21. http://dx.doi.org/10.1002/qj.2902.

Full text

APA, Harvard, Vancouver, ISO, and other styles

36

Castillo-Trujillo, Alma Carolina, Dale Partridge, Brian Powell, and Pierre Flament. "Vorticity Balance off the South Shore of Oahu, Hawaii, Derived by High-Frequency Radio Doppler Current Observations." Journal of Physical Oceanography 49, no. 1 (January 2019): 211–25. http://dx.doi.org/10.1175/jpo-d-17-0270.1.

Full text

Abstract:

AbstractHigh-frequency radio Doppler surface current observations off the south shore of Oahu, Hawaii, are used to calculate the vorticity equation at a ~2-km spatial resolution in terms of a time-dependent and time-mean surface balance. First-order terms are mean advection of mean vorticity, vortex stretching, and a residual, which is treated as unquantified terms such as wind stress curl, bottom pressure torque, and noise. The most striking feature in the 2-yr time-mean vorticity balance is the anticorrelation between advection of vorticity and vortex stretching implying that potential vorticity (PV) advection is the most dominant mechanism in the area. Several terms in the depth-integrated vorticity balance were also estimated. The bottom pressure torque acts as a first-order term only in areas of shallow topography. A PV analysis resulted in the 50-m Penguin Bank steering the westward Hawaiian Lee Current.

APA, Harvard, Vancouver, ISO, and other styles

37

Gupta, I. N., C. S. Lynnes, and R. A. Wagner. "An array study of the effects of a known local scatterer on regional phases." Bulletin of the Seismological Society of America 83, no. 1 (February 1, 1993): 53–63. http://dx.doi.org/10.1785/bssa0830010053.

Full text

Abstract:

Abstract F-k analyses of NORESS array recordings of teleseismic events have indicated a prominent secondary source about 25 to 30 km southwest of the array, in the region of Lake Mjosa with large topographical relief. Residual seismograms derived by subtracting the beamed record from each array channel are used to investigate the effects of this scatterer on the regional phases Pn, Pg, and Lg from several events at regional distances. The beamed record for each regional phase is obtained by incorporating steering delays based on the known azimuth and phase velocity from the f-k analysis of raw data. Both explosion and earthquake sources along several different azimuths to NORESS provide evidence for scattered arrivals Pn-to-Rg, Pg-to-Rg, and Lg-to-Rg, originating from the same region of Lake Mjosa. These scattered arrivals are observed with remarkable clarity and closeness to the expected arrival times and are rich in low frequencies, as expected for Rg. Their presence in various regional phases indicates that near-receiver scattering plays an important role in the composition of regional phases.

APA, Harvard, Vancouver, ISO, and other styles

38

Zhang, Yuanchun, Fuqing Zhang, and Jianhua Sun. "Comparison of the diurnal variations of warm-season precipitation for East Asia vs. North America downstream of the Tibetan Plateau vs. the Rocky Mountains." Atmospheric Chemistry and Physics Discussions 14, no. 9 (May 27, 2014): 13769–816. http://dx.doi.org/10.5194/acpd-14-13769-2014.

Full text

Abstract:

Abstract. A wavenumber-frequency spectral decomposition technique is used to analyze the high-resolution NOAA/Climate Prediction Center morphing technique (CMORPH) precipitation dataset and to explore the differences and similarities of the diurnal variation of warm-season precipitation in the East Asia and North America downstream of big topography. The predominant phase speed of precipitation at different time scales for North America, averaged over all warm-season months (May–August) for 2003–2010, is ∼20 m s−1, which is faster than the speed of ∼14 m s−1 calculated for East Asia. Consistent with the recent studies of the precipitation diurnal cycles for these two regions, the difference in the diurnal phase propagation is likely due to the difference in the mean steering level wind speed for these two regions. The wavenumber-frequency spectral analysis further reveals the complex, multi-scale, multi-modal nature of the warm-season precipitation variation embedded within the diurnal cycle over both continents, with phase speeds varying from 10 to 30 m s−1 and wave periods varying from diurnal to a few hours. At the diurnal frequency regulated by the thermodynamically driven Mountains-Plains Solenoids (MPS), increased precipitation for both continents first originates in the afternoon from the eastern edge of big topography and subsequently moves downslope in the evening and reaches the broad plains area at night. More complex diurnal evolutions are observed in East Asia due to more the complex, multistep terrains east of the Tibetan Plateau and the associated localized MPS circulations. Nevertheless, increased variation of precipitation at smaller spatial and temporal scales is evident in the active phase of the dominant diurnal cycle for both continents.

APA, Harvard, Vancouver, ISO, and other styles

39

Zhang, Yuanchun, Fuqing Zhang, and Jianhua Sun. "Comparison of the diurnal variations of warm-season precipitation for East Asia vs. North America downstream of the Tibetan Plateau vs. the Rocky Mountains." Atmospheric Chemistry and Physics 14, no. 19 (October 13, 2014): 10741–59. http://dx.doi.org/10.5194/acp-14-10741-2014.

Full text

Abstract:

Abstract. A wave-number-frequency spectral decomposition technique is used to analyze the high-resolution NOAA/Climate Prediction Center morphing technique (CMORPH) precipitation data set and to explore the differences and similarities of the diurnal variation of warm-season precipitation in the East Asia and North America downstream of big topography. The predominant phase speed of precipitation at different time scales for North America, averaged over all warm-season months (May–August) for 2003–2010, is ~20 ms−1, which is faster than the speed of ~14 ms−1 calculated for East Asia. Consistent with the recent studies of the precipitation diurnal cycles for these two regions, the difference in the diurnal phase propagation is likely due to the difference in the mean steering level wind speed for these two regions. The wave-number-frequency spectral analysis further reveals the complex, multi-scale, multi-modal nature of the warm-season precipitation variation embedded within the diurnal cycle over both continents, with phase speeds varying from 10 to 30 ms−1 and wave periods varying from diurnal to a few hours. At the diurnal frequency regulated by the thermodynamically driven mountains–plains solenoids (MPSs), increased precipitation for both continents first originates in the afternoon from the eastern edge of big topography and subsequently moves downslope in the evening and reaches the broad plains area at night. More complex diurnal evolutions are observed in East Asia due to the more complex, multistep terrains east of the Tibetan Plateau and the associated localized MPS circulations. Nevertheless, increased variation of precipitation at smaller spatial and temporal scales is evident in the active phase of the dominant diurnal cycle for both continents.

APA, Harvard, Vancouver, ISO, and other styles

40

CHIU, YUNG-SHENG, YUAN-YING CHANG, LI-WEN HSIEH, MEI-CHUN YUAN, and CHI-FANG CHEN. "THREE-DIMENSIONAL ACOUSTICS EFFECTS IN THE ASIAEX SCS EXPERIMENT." Journal of Computational Acoustics 17, no. 01 (March 2009): 11–27. http://dx.doi.org/10.1142/s0218396x09003835.

Full text

Abstract:

A three-dimensional (3D) ocean environment is assimilated with measured ocean data in the ASIAEX SCS (Asian Seas International Acoustics EXperiment, South China Sea) experiment. The experiment site is characterized as an active internal wave propagation region along the Northwestern shelf break of the South China Sea. Three-dimensional acoustics effects in the area are studied using FOR3DW, a wide-angle version of the parabolic equation code FOR3D (a Finite difference solution, an Ordinary differential equation, and Rational function approximations for solving 3D problems), and MOS3DPEF (MOdal Spectrum analysis based on 3D PE Field). The TL comparison between Nx2D and 3D calculations are shown to demonstrate the 3D effects. Variations in topography of the shelf break and in the water column due to the internal waves cause the 3D effects in the acoustic field. The intercomparison of the importance of bottom steering 3D effects and nonlinear internal wave refraction 3D effects is therefore proposed to realize which possesses the major part of the 3D effects. Also, 3D modal analysis results show that the nonlinear internal wave front causes severe horizontal refraction for higher modes.

APA, Harvard, Vancouver, ISO, and other styles

41

Heimbach, Patrick, and Martin Losch. "Adjoint sensitivities of sub-ice-shelf melt rates to ocean circulation under the Pine Island Ice Shelf, West Antarctica." Annals of Glaciology 53, no. 60 (2012): 59–69. http://dx.doi.org/10.3189/2012/aog60a025.

Full text

Abstract:

AbstractWe investigate the sensitivity of sub-ice-shelf melt rates under Pine Island Ice Shelf, West Antarctica, to changes in the oceanic state using an adjoint ocean model that is capable of representing the flow in sub-ice-shelf cavities. The adjoint code is based on algorithmic differentiation (AD) of the Massachusetts Institute of Technology’s ocean general circulation model (MITgcm). The adjoint model was extended by adding into the AD process the corresponding sub-ice-shelf cavity code, which implements a three-equation thermodynamic melt-rate parameterization to infer heat and freshwater fluxes at the ice-shelf/ocean boundary. The inferred sensitivities reveal dominant timescales of 30–60 days over which the shelf exit is connected to the deep interior via advective processes. They exhibit rich three-dimensional time-evolving patterns that can be understood in terms of a combination of the buoyancy forcing by inflowing water masses, the cavity geometry and the effect of rotation and topography in steering the flow in the presence of prominent features in the bedrock bathymetry. Dominant sensitivity pathways are found over a sill, as well as ‘shadow regions’ of very low sensitivities. To the extent that these transient patterns are robust they carry important information for decision-making in observation deployment and monitoring.

APA, Harvard, Vancouver, ISO, and other styles

42

Radhadevi, P. V., S. S. Solanki, M. V. Jyothi, and G. Varadan. "Automated Registration of Images from Multiple Bands of Resourcesat-2 Liss-4 camera." ISPRS - International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences XL-8 (November 28, 2014): 1177–83. http://dx.doi.org/10.5194/isprsarchives-xl-8-1177-2014.

Full text

Abstract:

Continuous and automated co-registration and geo-tagging of images from multiple bands of Liss-4 camera is one of the interesting challenges of Resourcesat-2 data processing. Three arrays of the Liss-4 camera are physically separated in the focal plane in alongtrack direction. Thus, same line on the ground will be imaged by extreme bands with a time interval of as much as 2.1 seconds. During this time, the satellite would have covered a distance of about 14 km on the ground and the earth would have rotated through an angle of 30”. A yaw steering is done to compensate the earth rotation effects, thus ensuring a first level registration between the bands. But this will not do a perfect co-registration because of the attitude fluctuations, satellite movement, terrain topography, PSM steering and small variations in the angular placement of the CCD lines (from the pre-launch values) in the focal plane. This paper describes an algorithm based on the viewing geometry of the satellite to do an automatic band to band registration of Liss-4 MX image of Resourcesat-2 in Level 1A. The algorithm is using the principles of photogrammetric collinearity equations. The model employs an orbit trajectory and attitude fitting with polynomials. Then, a direct geo-referencing with a global DEM with which every pixel in the middle band is mapped to a particular position on the surface of the earth with the given attitude. Attitude is estimated by interpolating measurement data obtained from star sensors and gyros, which are sampled at low frequency. When the sampling rate of attitude information is low compared to the frequency of jitter or micro-vibration, images processed by geometric correction suffer from distortion. Therefore, a set of conjugate points are identified between the bands to perform a relative attitude error estimation and correction which will ensure the internal accuracy and co-registration of bands. Accurate calculation of the exterior orientation parameters with GCPs is not required. Instead, the relative line of sight vector of each detector in different bands in relation to the payload is addressed. With this method a band to band registration accuracy of better than 0.3 pixels could be achieved even in high hill areas.

APA, Harvard, Vancouver, ISO, and other styles

43

Huang, Kuan-Chieh, and Chun-Chieh Wu. "The Impact of Idealized Terrain on Upstream Tropical Cyclone Track." Journal of the Atmospheric Sciences 75, no. 11 (October 16, 2018): 3887–910. http://dx.doi.org/10.1175/jas-d-18-0099.1.

Full text

Abstract:

Abstract Tropical cyclones (TCs) encountering the terrain of Taiwan usually experience prominent track deflection, resulting in uncertainty in TC track forecasts. The underlying mechanisms of TC deflection are examined to better understand the pattern of TC tracks under various flow regimes. In this study, idealized experiments are carried out utilizing the Advanced Research version of the Weather Research and Forecasting (WRF) Model. This study investigates the motion of a TC that is deflected southward while moving westward toward an idealized terrain similar to Taiwan. An analysis of both the flow asymmetries and the potential vorticity tendency (PVT) demonstrates that horizontal advection contributes to the southward movement of the TC. The track deflection is examined in two separate time periods, with different mechanisms leading to the southward movement. Changes in the background flow induced by the terrain first cause the large-scale steering current to push the TC southward while the TC is still far from the terrain. As the TC approaches the idealized topography, the role of the inner-core dynamics becomes important, and the TC terrain-induced channeling effect results in further southward deflection. Asymmetries in the midlevel flow also develop during this period, in part associated with the effect of vertical momentum transport. The combination of the large-scale environmental flow, the low-level channeling effect, and asymmetries in the midlevel flow all contribute to the southward deflection of the TC track.

APA, Harvard, Vancouver, ISO, and other styles

44

Rajnicek, A., and C. McCaig. "Guidance of CNS growth cones by substratum grooves and ridges: effects of inhibitors of the cytoskeleton, calcium channels and signal transduction pathways." Journal of Cell Science 110, no. 23 (December 1, 1997): 2915–24. http://dx.doi.org/10.1242/jcs.110.23.2915.

Full text

Abstract:

We exploited our observation that embryonic Xenopus spinal neurites align parallel to grooves in a quartz surface and that embryonic rat hippocampal neurites align perpendicular to shallow, narrow grooves (see companion paper: A. M. Rajnicek, S. Britland and C. D. McCaig, 1997) (J. Cell Sci. 110, 2905–2913) to investigate the mechanism of growth cone contact guidance. Substratum topography affected the pattern of growth cone filopodia and microtubules but parallel orientation of Xenopus neurites and perpendicular orientation of hippocampal neurites were unperturbed by cytochalasin B, which virtually eliminated filopodia. Hippocampal growth cone orientation and turning in response to grooves was unaffected by disruption of microtubules using taxol or nocodazole. Gross cytoskeletal reorganization on grooved substrata was therefore not required for growth cone steering. Inhibitors were used to identify the signal transduction pathway for perpendicular alignment of hippocampal neurites. Alignment persisted in the presence of gadolinium chloride, a blocker of stretch-activated calcium channels, the G protein inhibitor pertussis toxin, the protein tyrosine kinase inhibitor genistein, the protein kinase A and G inhibitor HA1004, the protein kinase A inhibitor KT5720and the protein kinase G inhibitor KT5823. Low concentrations of the protein kinase C inhibitors stauro-sporine, bisindolylmaleimide or H-7 did not affect perpendicular orientation but higher concentrations inhibited it. The calcium channel blockers flunarizine, nifedipine and diltiazem also inhibited perpendicular orientation. Influx of calcium and protein kinase C activity therefore appear to be involved in perpendicular contact guidance.

APA, Harvard, Vancouver, ISO, and other styles

45

DECKERS, B., E. KERSELAERS, H. GULINCK, B. MUYS, and M. HERMY. "Long-term spatio-temporal dynamics of a hedgerow network landscape in Flanders, Belgium." Environmental Conservation 32, no. 1 (March 2005): 20–29. http://dx.doi.org/10.1017/s0376892905001840.

Full text

Abstract:

Although the importance of hedgerows for sustainable agriculture and conservation of rural biodiversity is increasingly being recognized, obtaining insight into the spatial and temporal dynamics of hedgerow networks remains an important challenge for landscape ecologists, with the key factors driving changes in rural landscape structure especially deserving further attention. The present study analyses the long-term history of a hedgerow network landscape in Flanders, Belgium. A detailed reconstruction of the hedgerow network is made at five points in time, starting at the end of the 18th century until present, for 367 distinct 400 m×400 m samples. Whilst hedgerows were mainly concentrated around historical village centres and within valleys at the end of 18th century, the network expanded progressively during the 19th century. In the 20th century, the hedgerow network degraded strongly, with hedgerow density and connectivity declining and mesh-size heterogeneity and network fragmentation increasing, although the network recovered slightly during the 1990s. Different trajectories of change in hedgerow network structure were observed depending on landscape position, with both topography and village proximity significantly affecting hedgerow network dynamics. The present network structure was mainly governed by land use, with highly developed networks being predominantly associated with pasture. Three main conclusions arise from the results of this study. First, the role of land use and landscape position as basic factors steering hedgerow network dynamics at the landscape scale is demonstrated. Second, the long-term perspective of the study enabled insight into the poorly known expansion phase of hedgerow networks, linked mainly with the development of small-scale labour-intensive agriculture. Finally, the findings confirm the large-scale degradation of linear semi-natural habitats in European agricultural landscapes during most of the 20th century, and indicate that a pro-active rural policy can halt and even reverse this process.

APA, Harvard, Vancouver, ISO, and other styles

46

Blanckaert, K. "Topographic steering, flow recirculation, velocity redistribution, and bed topography in sharp meander bends." Water Resources Research 46, no. 9 (September 2010). http://dx.doi.org/10.1029/2009wr008303.

Full text

APA, Harvard, Vancouver, ISO, and other styles

47

Blanckaert, K. "Correction to “Topographic steering, flow recirculation, velocity redistribution, and bed topography in sharp meander bends”." Water Resources Research 46, no. 11 (November 2010). http://dx.doi.org/10.1029/2010wr010004.

Full text

APA, Harvard, Vancouver, ISO, and other styles

48

Thomson, Richard E. "Topographic steering of a mid-depth drifter in an eddy-like circulation region south and east of the Hawaiian Ridge." Journal of Geophysical Research 108, no. C11 (2003). http://dx.doi.org/10.1029/2002jc001715.

Full text

APA, Harvard, Vancouver, ISO, and other styles

49

Bestley, Sophie, Virginia Andrews-Goff, Esmee van Wijk, Stephen R. Rintoul, Michael C. Double, and Jason How. "New insights into prime Southern Ocean forage grounds for thriving Western Australian humpback whales." Scientific Reports 9, no. 1 (September 27, 2019). http://dx.doi.org/10.1038/s41598-019-50497-2.

Full text

Abstract:

Abstract Humpback whale populations migrate extensively between winter breeding grounds and summer feeding grounds, however known links to remote Antarctic feeding grounds remain limited in many cases. New satellite tracks detail humpback whale migration pathways from Western Australia into the Southern Ocean. These highlight a focal feeding area during austral spring and early summer at the southern Kerguelen plateau, in a western boundary current where a sharp northward turn and retroflection of ocean fronts occurs along the eastern plateau edge. The topographic steering of oceanographic features here likely supports a predictable, productive and persistent forage ground. The spatial distribution of whaling catches and Discovery era mark-recaptures confirms the importance of this region to Western Australian humpback whales since at least historical times. Movement modelling discriminates sex-related behaviours, with females moving faster during both transit and resident periods, which may be a consequence of size or indicate differential energetic requirements. Relatively short and directed migratory pathways overall, together with high-quality, reliable forage resources may provide a partial explanation for the ongoing strong recovery demonstrated by this population. The combination of new oceanographic information and movement data provides enhanced understanding of important biological processes, which are relevant within the context of the current spatial management and conservation efforts in the Southern Ocean.

APA, Harvard, Vancouver, ISO, and other styles

50

Lim, Aaron, Andrew J. Wheeler, David M. Price, Luke O’Reilly, Kimberley Harris, and Luis Conti. "Influence of benthic currents on cold-water coral habitats: a combined benthic monitoring and 3D photogrammetric investigation." Scientific Reports 10, no. 1 (November 10, 2020). http://dx.doi.org/10.1038/s41598-020-76446-y.

Full text

Abstract:

Abstract Strong currents are a key component of benthic habitats by supplying food and nutrients to filter-feeding organisms such as cold-water corals. Although field measurements show that cold-water coral habitats exist in areas of elevated bottom currents, flume studies show that cold-water corals feed more effectively at lower flow speeds. This research aims to explore this disconnect in situ by utilising high spatial resolution ROV photogrammetric data coupled with high temporal resolution in situ acoustic doppler current profile measurements at seven study sites within the upper Porcupine Bank Canyon (uPBC), NE Atlantic. Object-based image analysis of photogrammetric data show that coral habitats vary considerably within the upper canyon. Although there is a regional hydrodynamic trend across the uPBC, this variation is likely driven locally by topographic steering. Although live coral tends not to face directly into the prevailing current direction, preferring lower local flows speeds, they can tolerate exposure to high-flow speeds of up to 114 cm s−1, the highest recorded in a Desmophyllum pertusum habitat. Not only do these high flow speeds supply food and nutrients, they may also help contribute to coral rubble production through physical erosion. These results can be incorporated into simulations of future deep-water habitat response to changing environmental conditions while extending the upper current speed threshold for cold-water corals.

APA, Harvard, Vancouver, ISO, and other styles

Journal articles on the topic 'Topographic steering'

Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles