Keywords:
Submarine canyon
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본 논문에서는 낙동강 하구역 진우도 자연해빈을 대상으로 해안표착물과 식생대 전선의 상관성 및 상호거동에 대하여 연구하였다. 해안표착물과 식생대 주변의 비사에 의한 퇴적 특성을 고찰하기 위해 현장 바람과 바닥조건을 고려하여 실내 풍동실험을 수행하였다. 본 연구에서 고려하는 주요 영향은 해안표착물과 식생대 주변의 바람에 의한 모래의 퇴적현상이다. 해안표착물에 대한 실험결과로서, 모형 전면부터 퇴적되고 퇴적된 높이가 모형의 70% 정도 퇴적되었을 때 모형 후면이 퇴적되는 양상이 나타났다. 이에 반해, 식생을 대상으로 한 실험에서는 모형 전면보다 후면이 먼저 퇴적되고, 후면이 전면보다 60%정도 더 높게 쌓이는 양상이 나타났다.
Deposition
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Wind is one of the exogenic forces shaping landscapes.Wind erosion is one of the main geomorphologic processes in arid,semiarid and cold-alpine regions.Except forming various wind-eroded landforms,wind erosion can result in soil erosion,increase of land surface roughness,land degradation and desertification.Moreover,wind erosion can produce atmospheric aerosols in a big quantity to pollute air and affect directly or indirectly the atmospheric radiation balance and even global climate change.Wind erosion is caused by both natural and artificial factors.In order to thoroughly reveal the occurrence mechanism of wind erosion,in this paper,the data of the wind profile from wind tunnel experiments are used to study the characteristics of turbulent transmission with wind speed over the vegetation-uncovered sandy bed,gravel bed and vegetation-gravel bed in arid and semiarid regions by using aerodynamic methods.The results are as follows:(1) The turbulent transmission intensity is increased with the increase of free wind speed,sand grain size and land surface roughness;(2) The turbulent transmission intensity is closely related to the density of roughness elements,it is increased with the increase of roughness element density when the density is low,and its change curve becomes gentle when the density reaches a certain value.The study results have certain reference and guiding significance for further researching the relationship between the turbulent transmission and turbulent energy dissipation near the ground surface and for revealing the wind erosion mechanism.
Desertification
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Abstract Small scale features resulting from wind erosion are widespread in the Namib Desert. They include selective erosion of lithological variations (etching), flutes and grooves, facetting of clasts and residual boulders, and smoothing and polishing of rock surfaces. Large scale features are tentatively identified and are restricted to the southern Namib, with its high energy, unidirectional wind regime. Wind erosion features are best developed on fine‐grained rocks of intermediate hardness. They are oriented towards or parallel to modern strong winds. The turbulent flow of wind armed only with dust particles is probably more important than wind driven sand in creating smooth polished rock surfaces, flutes, and grooves. Wind driven sand appears to be significant only in facetting rock masses.
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Intermittency
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Abstract Flow dynamics and sand deposition processes over nebkhas were investigated using computational fluid dynamics simulations, wind tunnel experiments, and field measurements. The computational fluid dynamics simulations showed that nebkha width affects both the elongation and broadening of the wind shadows. The length of the wind shadows decreased as the wind shear velocity increased, following a power function, irrespective of the width and height of the nebkha. There are some uncertainties about the effect of the aspect ratio of the nebkha on the formation of wind shadows as a result of the omission of the transport of sand in the simulations. It is suggested that the length of wind shadows is dependent on the absolute values of nebkha width and height rather than the nebkha aspect ratio. Although the numerical results were consistent with the results of the wind tunnel experiments, the wind tunnel experiments showed that the height of the nebkha had a negative effect on the elongation of the shadow dunes. The sedimentary structures revealed by ground‐penetrating radar surveys of the dunes in the Taitema Dry Lake, in the eastern Taklimakan Desert, China, showed that the formation of shadow dunes can be divided into three phases. Shadow dunes are initially controlled by horizontal separation flow and then elongate following the same growth mechanisms as linear dunes, eventually breaking up into isolated barchans or short, temporary linear dunes. However, the formation of shadow dunes does not necessarily call for the three phases depending on the local wind regime and sediment supply.
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Aeolian sand transport is serious in many arid regions in the world,and it is considered to be as a significant part of global biogeochemical cycles.Furthermore,wind-blown sand brings often disasters.Therefore,widespread attention has been paid to the significance of aeolian sand transport in many fields,such as geomorphology,climatology,meteorology,ecology and environmental science.Wind-blown sand direction is a base for both studying the formation and evolution of aeolian geomorphology and carrying out the sand damage control measures.In this study,a statistical analysis on wind-blown sand direction in an oasis-desert ecotone in Qira County,located in the south marginal zone of the Tarim Basin,was carried out during the period from 2010 to 2011.Some preliminary conclusions are as follows:(1) In the study area,the wind directions of sand-driving wind are mainly W and WNW,and the change of wind direction is comparatively simple;(2) In the study area,the wind directions at which the values of sediment discharge are high are dominated by NW,WNW,W,SW and WSW,and the occurring frequency is as high as 68.3%.An aeolian sediment discharge of 96 kg passing through a height extent of 0-40 cm and 1-cm width occurred.The annual resultant wind-blown sand amount is 45.9 kg,and the resultant wind-blown sand direction is 102.5°;(3) In the study area,the wind-blown sand potential and resultant wind-blown sand potential are 43.2 VU and 31.04 VU respectively.There is a considerable difference between the direction of wind-blown sand potential and the measured sediment discharge.It is recognized that wind-blown sand is a complex process,and various factors affecting wind-blow sand,such as wind speed,wind direction and underlying surface,should be comprehensively considered and researched.
Ecotone
Aeolian sand
Prevailing winds
Katabatic wind
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Landform
Abrasion (mechanical)
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Variation (astronomy)
Plage
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