The transport of ye been investigated numerica Ilow sand over mountain regions in the presence of internal gravity waves has y. The motion of yellow sand particles has been simulated in a Lagrangian frame of reference...The transport of ye been investigated numerica Ilow sand over mountain regions in the presence of internal gravity waves has y. The motion of yellow sand particles has been simulated in a Lagrangian frame of reference by solving the time-dependent Reynolds averaged Navier-Stokes equations. An implicit time integration in a fitted body grid arrangement was used to simulate the stratified flow over an isolated ideally bell-shaped mountain. The transport and deposition of particles of various sizes, and of the altitudes where particles were released have been analyzed. Particular attention was given to transport patterns of different sized particles in various atmospheric conditions. The results show that the particle size and the release altitude are both important factors in determining the trajectories of the particles. Small particles tend to be transported a long distance over the mountains, whereas heavier particles settle down around the release source. Due to the existence of an internal gravity wave, the particle release altitude affects the trajectory of the particles. The analysis and results provide a very useful tool for the study of atmospheric flow and transport of pollutants over real topographies.展开更多
Based on one-year wave field data measured at the south part of the radial sand ridges of the Southern Yellow Sea, the wave statistical characteristics, wave spectrum and wave group properties are analyzed. The result...Based on one-year wave field data measured at the south part of the radial sand ridges of the Southern Yellow Sea, the wave statistical characteristics, wave spectrum and wave group properties are analyzed. The results show that the significant wave height （H1/3） varies from 0.15 to 2.22 m with the average of 0.59 m and the mean wave period （Tmean） varies from 2.06 to 6.82 s with the average of 3.71 s. The percentage of single peak in the wave spectra is 88.6 during the measurement period, in which 36.3% of the waves are pure wind waves and the rest are young swells. The percentage with the significant wave height larger than 1 m is 12.4. The dominant wave directions in the study area are WNW, W, ESE, E and NW. The relationships among the characteristic wave heights, the characteristic wave periods, and the wave spectral parameters are identified. It is found that the tentative spectral model is suitable for the quantitative description of the wave spectrum in the study area, while the run lengths of the wave group estimated from the measured data are generally larger than those in other sea areas.展开更多
The Jianggang Harbour-centered radial sand ridge(RSR) is the largest sand body in the Yellow Sea. Its formation and evolution are of interest for scientists of various fields; however, the sediment provenance is uncer...The Jianggang Harbour-centered radial sand ridge(RSR) is the largest sand body in the Yellow Sea. Its formation and evolution are of interest for scientists of various fields; however, the sediment provenance is uncertain. In this study, rare earth element(REE) geochemical compositions of the RSR sediments together with their potential sources are investigated to identify the provenance of the RSR sediments. The typical parameters((La/Yb)_N,(La/Sm)_N and(Gd/Yb)_N) as well as the upper continental crust-normalized patterns of REEs can only be associated with source rocks, and thus can be used as effective tracers for the origin and sources of sediments. However, the REE contents of sediments are affected by many factors, such as particle sorting and chemical weathering. Onshore RSR sediments are different in REE geochemical composition from offshore RSR sediments to some extent, suggesting that not all of the offshore RSR sediments have the same sources as the onshore RSR sediments. Meanwhile, the sediments adjacent to the northeast of Cheju Island and at Lian Island near the Lianyun Harbour were not the source of the RSR sediments due to their distinctive REE patterns, dEu,(La/Yb)_N,(Gd/Yb)_N and(La/Sm)_N. The Korean river sediments could be dispersed to the Jiangsu Coast slightly impacting the fine fractions of the RSR sediments, particularly the offshore RSR sediments. Additionally, geochemical comparisons show that the modern Yellow River was responsible for the onshore RSR sediments, whereas the sediment loads from the Yangtze River could serve as a major contributor to the RSR, particularly the offshore RSR. In addition, the offshore RSR could also be partly fed by an unknown source due to some high values of(La/Yb)_N,(La/Sm)_N and La contents differing from those of the Chinese and Korean river sediments.展开更多
According to a deformed mild-slope equation derived by Guang-wen Hong and an enhanced numerical method, a wave refraction-diffraction nonlinear mathematical model that takes tidal level change and the high-order bathy...According to a deformed mild-slope equation derived by Guang-wen Hong and an enhanced numerical method, a wave refraction-diffraction nonlinear mathematical model that takes tidal level change and the high-order bathymetry factor into account has been developed. The deformed mild-slope equation is used to eliminate the restriction of wave length on calculation steps. Using the hard disk to record data during the calculation process, the enhanced numerical method can save computer memory space to a certain extent, so that a large-scale sea area can be calculated with high-resolution grids. This model was applied to wave field integral calculation over a radial sand ridge field in the South Yellow Sea. The results demonstrate some features of the wave field： （1） the wave-height contour lines are arc-shaped near the shore; （2） waves break many times when they propagate toward the shore; （3） wave field characteristics on the northern and southern sides of Huangshayang are different; and （4） the characteristics of wave distribution match the terrain features. The application of this model in the region of the radial sand ridge field suggests that it is a feasible way to analyze wave refraction-diffraction effects under natural sea conditions.展开更多
黄河流域是我国重要的生态屏障和经济区,防风固沙服务及其驱动机制的研究对于筑牢黄河流域生态安全屏障具有重要意义。基于修正土壤风蚀模型(RWEQ)定量评估黄河流域2000—2018年防风固沙服务时空变化,采用相关分析和地理加权回归模型(G...黄河流域是我国重要的生态屏障和经济区,防风固沙服务及其驱动机制的研究对于筑牢黄河流域生态安全屏障具有重要意义。基于修正土壤风蚀模型(RWEQ)定量评估黄河流域2000—2018年防风固沙服务时空变化,采用相关分析和地理加权回归模型(GWR)从社会、气候、土壤、植被、地形等角度探究各驱动因素对黄河流域防风固沙服务影响的空间异质性。结果表明:(1)2000—2018年黄河流域土壤风蚀模数与单位面积防风固沙量分别以0.04 t hm^(-2)a^(-1)和0.14 t hm^(-2)a^(-1)的速率下降,而防风固沙保有率和植被覆盖度则分别以0.05%·a^(-1)和0.26%·a^(-1)的速率上升。(2)黄河流域土壤风蚀以微度(<2 t hm^(-2)a^(-1))和轻度(2—25 t hm^(-2)a^(-1))为主,共占研究区面积的96.28%。土壤风蚀在空间分布呈现西北高东南低的特点,而防风固沙服务高值则主要分布于西北部和下游流域。(3)各驱动因素对黄河流域防风固沙服务的影响具有明显的空间异质性,其中降水、温度、实际蒸散量、土壤黏粒含量、土壤有机质含量和坡度以负面抑制作用为主,而风速、气压、归一化植被指数和土壤粗砂含量则主要呈现正向促进作用。本研究结果可为黄河流域荒漠化防治和生态保护修复提供一定参考和依据。展开更多
基金the Scientific Foundation for Returned Overseas Chinese Scholars, Ministry of Education of China
文摘The transport of ye been investigated numerica Ilow sand over mountain regions in the presence of internal gravity waves has y. The motion of yellow sand particles has been simulated in a Lagrangian frame of reference by solving the time-dependent Reynolds averaged Navier-Stokes equations. An implicit time integration in a fitted body grid arrangement was used to simulate the stratified flow over an isolated ideally bell-shaped mountain. The transport and deposition of particles of various sizes, and of the altitudes where particles were released have been analyzed. Particular attention was given to transport patterns of different sized particles in various atmospheric conditions. The results show that the particle size and the release altitude are both important factors in determining the trajectories of the particles. Small particles tend to be transported a long distance over the mountains, whereas heavier particles settle down around the release source. Due to the existence of an internal gravity wave, the particle release altitude affects the trajectory of the particles. The analysis and results provide a very useful tool for the study of atmospheric flow and transport of pollutants over real topographies.
文摘Based on one-year wave field data measured at the south part of the radial sand ridges of the Southern Yellow Sea, the wave statistical characteristics, wave spectrum and wave group properties are analyzed. The results show that the significant wave height （H1/3） varies from 0.15 to 2.22 m with the average of 0.59 m and the mean wave period （Tmean） varies from 2.06 to 6.82 s with the average of 3.71 s. The percentage of single peak in the wave spectra is 88.6 during the measurement period, in which 36.3% of the waves are pure wind waves and the rest are young swells. The percentage with the significant wave height larger than 1 m is 12.4. The dominant wave directions in the study area are WNW, W, ESE, E and NW. The relationships among the characteristic wave heights, the characteristic wave periods, and the wave spectral parameters are identified. It is found that the tentative spectral model is suitable for the quantitative description of the wave spectrum in the study area, while the run lengths of the wave group estimated from the measured data are generally larger than those in other sea areas.
基金Under the auspices of National Key Technology Research and Development Program(No.2012BAB03B01)National Natural Science Foundation of China(No.41273015,51278172,51478167)
文摘The Jianggang Harbour-centered radial sand ridge(RSR) is the largest sand body in the Yellow Sea. Its formation and evolution are of interest for scientists of various fields; however, the sediment provenance is uncertain. In this study, rare earth element(REE) geochemical compositions of the RSR sediments together with their potential sources are investigated to identify the provenance of the RSR sediments. The typical parameters((La/Yb)_N,(La/Sm)_N and(Gd/Yb)_N) as well as the upper continental crust-normalized patterns of REEs can only be associated with source rocks, and thus can be used as effective tracers for the origin and sources of sediments. However, the REE contents of sediments are affected by many factors, such as particle sorting and chemical weathering. Onshore RSR sediments are different in REE geochemical composition from offshore RSR sediments to some extent, suggesting that not all of the offshore RSR sediments have the same sources as the onshore RSR sediments. Meanwhile, the sediments adjacent to the northeast of Cheju Island and at Lian Island near the Lianyun Harbour were not the source of the RSR sediments due to their distinctive REE patterns, dEu,(La/Yb)_N,(Gd/Yb)_N and(La/Sm)_N. The Korean river sediments could be dispersed to the Jiangsu Coast slightly impacting the fine fractions of the RSR sediments, particularly the offshore RSR sediments. Additionally, geochemical comparisons show that the modern Yellow River was responsible for the onshore RSR sediments, whereas the sediment loads from the Yangtze River could serve as a major contributor to the RSR, particularly the offshore RSR. In addition, the offshore RSR could also be partly fed by an unknown source due to some high values of(La/Yb)_N,(La/Sm)_N and La contents differing from those of the Chinese and Korean river sediments.
基金supported by the Ph.D. Programs Foundation of the Ministry of Education of China (Grant No.20070294026)
文摘According to a deformed mild-slope equation derived by Guang-wen Hong and an enhanced numerical method, a wave refraction-diffraction nonlinear mathematical model that takes tidal level change and the high-order bathymetry factor into account has been developed. The deformed mild-slope equation is used to eliminate the restriction of wave length on calculation steps. Using the hard disk to record data during the calculation process, the enhanced numerical method can save computer memory space to a certain extent, so that a large-scale sea area can be calculated with high-resolution grids. This model was applied to wave field integral calculation over a radial sand ridge field in the South Yellow Sea. The results demonstrate some features of the wave field： （1） the wave-height contour lines are arc-shaped near the shore; （2） waves break many times when they propagate toward the shore; （3） wave field characteristics on the northern and southern sides of Huangshayang are different; and （4） the characteristics of wave distribution match the terrain features. The application of this model in the region of the radial sand ridge field suggests that it is a feasible way to analyze wave refraction-diffraction effects under natural sea conditions.
文摘黄河流域是我国重要的生态屏障和经济区,防风固沙服务及其驱动机制的研究对于筑牢黄河流域生态安全屏障具有重要意义。基于修正土壤风蚀模型(RWEQ)定量评估黄河流域2000—2018年防风固沙服务时空变化,采用相关分析和地理加权回归模型(GWR)从社会、气候、土壤、植被、地形等角度探究各驱动因素对黄河流域防风固沙服务影响的空间异质性。结果表明:(1)2000—2018年黄河流域土壤风蚀模数与单位面积防风固沙量分别以0.04 t hm^(-2)a^(-1)和0.14 t hm^(-2)a^(-1)的速率下降,而防风固沙保有率和植被覆盖度则分别以0.05%·a^(-1)和0.26%·a^(-1)的速率上升。(2)黄河流域土壤风蚀以微度(<2 t hm^(-2)a^(-1))和轻度(2—25 t hm^(-2)a^(-1))为主,共占研究区面积的96.28%。土壤风蚀在空间分布呈现西北高东南低的特点,而防风固沙服务高值则主要分布于西北部和下游流域。(3)各驱动因素对黄河流域防风固沙服务的影响具有明显的空间异质性,其中降水、温度、实际蒸散量、土壤黏粒含量、土壤有机质含量和坡度以负面抑制作用为主,而风速、气压、归一化植被指数和土壤粗砂含量则主要呈现正向促进作用。本研究结果可为黄河流域荒漠化防治和生态保护修复提供一定参考和依据。
