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  • 2011 Volume 66 Issue 3
    Published: 20 March 2011
      
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  • Sediment Exchange and Transport Processes in the Yangtze River Estuary: Concurrent Discussion on the Effects of Sediment Sink in the Muddy Area
    LIU Hong, HE Qing, Gert Jan WELTJE, CHEN Jiyu
    2011, 66(3): 291-304. https://doi.org/10.11821/xb201103001
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    The suspended & surface sediments exchange processes under the high-turbidity and mixing estuarine environments were analyzed based on the grain size spectral calculation, to explore the rate and transport of suspended sediments in the Yangtze estuary-shelf systems. The results showed that: (1) approximately 47% of the sediments from the Yangtze River was accumulated in the mouth bar area and subaqueous delta, while the rest was transported to the Hangzhou Bay and southern Zhejiang and Fujian coasts. 122.5°-123°E was the important limits of the Yangtze suspended sediment diffusing eastward to the East China Sea. This method of grain size spectral calculation provided by this paper can be used for the study of quantitative calculation of sediment transport and deposition in other tidal environments. (2) Higher sediment exchange ratio (p> 0.6) occurred in the muddy area and Hangzhou Bay, and the ratio of the muddy areas outside the South Passage was higher than 0.9, which indicates that most suspended sediment contributed to the seabed evolution and sediment supply. On the decadal to centennial time scale associated with our results, a clearly defined depocenter of Yangtze sediment with the exchange rates greater than 2-3 cm/a is present in the muddy area and Hangzhou Bay. (3) Due to the impact of longshore currents and the Taiwan warm current, the suspended sediment from the Yangtze River deposited firstly in the muddy area, and then was transported to the inner Yangtze River Estuary, Hangzhou Bay and the south coasts by tidal current. Muddy area was the "sediment sink" of sediment processes in the estuary and moved southward. (4) Under the background of decrease in the Yangtze River sediment supply, the delta toward tidal flats was still deposited slowly, indicating that the sediments in the sediment sink made great contribution to the estuarine geomorphologic evolution.
  • Morphological Evolution of Mouth Bars of the Yangtze Estuarine Waterways in the Last 100 Years
    HE Yufang, CHENG Heqin, CHEN Jiyu
    2011, 66(3): 305-312. https://doi.org/10.11821/xb201103002
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    The mouth bar in the Yangtze estuarine waterways has significant influences on the transportation of the estuary, flood discharge and the construction of Shanghai Port. In this paper the morphological evolution and its mechanisms of mouth bars of the Yangtze estuarine waterways are studied by analyzing hundreds of years of historical data and the latest profile maps of some main mouth bar channels in the Yangtze Estuary. The results are shown as follows: The mouth bars in North Branch move gradually from outside of the mouth to inside and form a huge sand bar. In North Channel, the top of mouth bar migrates down-stream about 30 kilometers, and a channel bar has been developing since 2001. Two mouth bar tops had ever exited in North Passage, which disappeared in 2010. The top of mouth bar in South Passage migrates to down-stream about 14 kilometers and the number of tops increases at first and then reduces to only one now. According to these analysis results, we can conclude that the evolution of mouth bar differs from that of the location. In North Branch it is directly related to large reclamation in Chongming Island, but in North Passage it has a close relationship with the Yangtze Estuary Deepwater Channel Regulation. However, the evolution of mouth bar in North Channel and South Passage is not only in connection with the Yangtze Estuary Deepwater Channel Regulation, but also with the reclamation in East Hengsha Shoal and the Qingcaosha Reservoir.
  • Multi-scale Variability of Flow Discharge and Sediment Load of Yellow River to Sea and Its Impacts on the Estuary during the Past 60 Years
    LIU Feng, CHEN Shenliang, PENG Jun, CHEN Guangquan
    2011, 66(3): 313-323. https://doi.org/10.11821/xb201103003
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    Based on the hydrological data of Lijin station from 1950 to 2008, the temporal change of flow discharge and sediment load of Yellow River to sea is analyzed by the wavelet analyses. What's more, the impacts of their changes on the estuary are studied based on the measured coastline and bathometric data. The results show that there are three significant periodic variations for flow discharge and sediment load, which may be related with the periodic variations of ENSO, additionally, the variations of flow discharge and sediment load are varying in different time scales. The long-term variation of flow discharge and sediment load are stepwise decreasing because of the combined influences of human activities and precipitation. The evolution of the Yellow River Estuary is in relation with the flow discharge and sediment load, the stretch speed of its coastline in different periods is significantly correlated with the incoming flow discharge and sediment load, and the subaqueous topography near the estuary has exhibited siltation generally since 1976. Furthermore, the siltation extent is closely related with the flow discharge and sediment load into sea.
  • Scour and Silting Evolution and Its Influencing Factors in Inner Mongolia Reach
    QIN Yi, ZHANG Xiaofang, WANG Fenglong, YAN Heng, HAN Haijun
    2011, 66(3): 324-330. https://doi.org/10.11821/xb201103004
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    Rivers with fluvial equilibrium are characterized by bed deformation adjustment. The erosion-deposition area in cross-section can reflect this characteristic. The time series of erosion-deposition area in BYGL and SHHK stations was obtained by quantifying change of section area during the period 1976-2006. After trend and mutation analysis, three different trends were identified in general: the quasi-equilibrium phase, rapid shrinkage phase and the new quasi-equilibrium phase. It was also found that once a big flood occurred in the ten tributaries, the trend of erosion-deposition area would change. The phenomenon was more obvious due to the decrease of deluge after the completion of upstream reservoir. After the time series had clear mutations in the late 1990s, the Inner Mongolia reach entered a new equilibrium phase. The conditions of incoming water and sediment were adapted to the bed boundary conditions. Therefore, how to control sedimentation in Inner Mongolia reach was worth discussing.
  • Scale Effects of China Mainland Coastline Based on Fractal Theory
    GAO Yi, SU Fenzhen, ZHOU Chenghu, YANG Xiaomei, SUN Xiaoyu, ZHANG Dandan
    2011, 66(3): 331-339. https://doi.org/10.11821/xb201103005
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    Based on DEM and remote sensing images, multi-scale coastlines of China mainland were extracted and the fractal characteristics of coastlines were analyzed. The results are shown as follows. (1) The coastline of China mainland fits the fractal model, and the fractal dimension is 1.195. (2) The scale effect with fractal dimensions of coastline has significant differences in light of uplift and subsidence segments along the coast of China mainland. (3) The fractal numbers of coastline dimension have significant spatial heterogeneity in the coastline types. The number of fractal dimension in sandy coastline located in the Luanhe River plain is 1.109, for the muddy coastline located in northern Jiangsu Plain, 1.059, and for rocky coastline along southeastern Fujian mountains, 1.293. (4) The length of rocky coastline is affected more by scale effect than that of muddy and sandy coastline. Since coastline is the conjunction of sea, land and atmosphere surface, the study of coastline scale effect is one of the scientific bases for the research on air-sea-land interaction in multi-scales.
  • The Study of Marine Terraces on Matsu Islands
    TUNG Terhuei, WANG Huati, TENG Kouhsiung
    2011, 66(3): 340-347. https://doi.org/10.11821/xb201103006
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    The tectonic movements of Pingtan-Dongshan fold belt and Changleh-Zhao'an fault zone occurred in late Jurassic. Due to the influence of tectonic movement and magmatic activities, formed a series of islands off the coast of southeast China including the Matsu Islands. The results show that the Matsu Islands have 9 marine terraces, with heights of 0-10 m, 20-38 m, 40-56 m, 58-78 m, 80-97 m, 100-128 m, 142-160 m, 172-182 m and 238-248 m. Based on the relationship of late Pleistocene marine terraces sequence and uplift rate base map, we have estimated formation age of various marine terraces, i.e., 6 ka BP, 46 ka BP, 55 ka BP, 76 ka BP, 79 ka BP, 94 ka BP, 105 ka BP, 119 ka BP and 175 ka BP. The terraces formed in Pleistocene except the first step in Pliocene. The basement average uplift rate is estimated to be 1.6 mm/a after we compared the height and spacing of marine terraces on the Matsu Islands.
  • Formation Mechanism and Stability of Caofeidian Channel in the Bohai Bay
    JI Rongyao, LU Yongjun, ZUO Liqin
    2011, 66(3): 348-355. https://doi.org/10.11821/xb201103007
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    Caofeidian barrier island extends southward into the Bohai Bay in the form of headland, just in front of which there is a deep channel with the largest water depth of 41 m. The formation of the deep channel was based on the old river valley extending from the Haihe River Estuary to the Bohai Sea Strait. The headland topography of Caofeidian barrier island forms the boundary condition of the deep channel, and the obvious velocity increase by headland effect becomes the dynamic condition of the deep channel development. The boundary condition and dynamic condition for the deep channel are almost adaptive for a long time, and the seabed is basically in a state of stability, and the the deep channel is in a state of slight erosion with short sediment supply. In recent years, the development of the Caofeidian harbor area has a significant effect on the evolution of the deep channel. The engineering practice shows that during 2004-2009, the seabed is basically in a state of erosion-deposition equilibrium with slight ersoion, and the deep channel is stable, which proves that the development of the Caofeidian harbor area did not change the boundary and dynamic conditions of the deep channel.
  • Application of MODIS BRDF/Albedo Dataset in the Regional Temperature Simulation of China
    ZHANG Xuezhen, ZHENG Jingyun, HE Fanneng, WANG Zhuosen
    2011, 66(3): 356-366. https://doi.org/10.11821/xb201103008
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    Surface albedo determines the surface radiation budget directly and causes a local radiation forcing, thus the local temperature (2 m temperature, the same below) could be modified; and then, through atmospheric advection, the temperature of lower reach would be impacted. To study the effects of using MODIS BRDF/Albedo in the regional climate simulation with WRF (Weather Research and Forecasting) model, we carried out two 6-year (2002-2007) simulations on climate of China with WRF model. The Control Run (CT) was forced by surface albedo derived from Static Surface Dataset suggested by WRF model; the MODIS Run (MD) was forced by spectral surface albedo derived from MODIS BRDF/Albedo dataset. The results show the CT run could reproduce the general spatial pattern of temperature with evident biases. In southern Tibetan Plateau, the CT's simulation is lower than observation, with the maximum biases of 1.03oC in autumn; while, in eastern China, the CT's simulation is higher than observation, with the maximum biases of 3.4oC in spring. MD's biases pattern is similar with CT run. However, the MD's cooling biases in southern Tibetan Plateau are larger than CT run, with the maximum biases of 1.32oC; the MD's warming biases in eastern China is lower than CT run, with the maximum biases of 2.97oC. The differences between the CT's biases and MD's biases demonstrate MD's simulation is generally lower than CT's simulation. On the Tibetan Plateau, the lower simulation from MD is attributed to local higher surface albedo. The higher surface albedo causes a less net solar radiation and then a less sense heat from surface to atmosphere bottom; as a consequence, the lower temperature happened. In eastern China, the lower temperature was attributed to colder airflow from north, which is caused by higher albedo and thus cooling effects occur on the Mongolia Plateau.
  • Study on Tropical Cyclone Potential Impact Index in China
    YIN Yizhou, XIAO Fengjin, LUO Yong, ZHAO Shanshan
    2011, 66(3): 367-375. https://doi.org/10.11821/xb201103009
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    Based on tropical cyclone traces and disasters information, considering the tropical cyclone frequency, intensity, scope and duration, the study established the Tropical Cyclone Potential Impact Index (TCPI). It also analyzed the spatial pattern and interannual variations of TCPI for China during 1949-2009. As an example, the Super Typhoon "Saomai" (No.0608) was selected to analyze the relationship between TCPI and the direct economic losses, total rainfall, and maximum wind speed. The research had the following results: China's TCPI presented a weak decreasing trend during 1949-2009 and this trend was not significant, but in different phases the decreasing or increasing trend was more significant. The tropical cyclones potential impact decreased in coastal provinces of southern China such as Hainan, Guangdong and Guangxi while it increased in southeastern coastal provinces such as Zhejiang, Fujian and Taiwan in recent 20 years. Highest TCPI is mainly observed in Taiwan, Hainan, Guangdong coast, Fujian coast and southern Zhejiang coast. TCPI has good correlation with the direct economic losses, rainfall and maximum wind speed, and the correlation is significant at the 0.01 level.
  • Inhomogeneity Characteristics of Intra-annual Precipitation over the Tibetan Plateau in Recent 42 Years
    YANGWei, HE Jinhai, WANG Panxing,WANG Chuanhui
    2011, 66(3): 376-384. https://doi.org/10.11821/xb201103010
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    Based on the daily precipitation datasets from 1967 to 2008 recorded at stations over the Tibetan Plateau, the precipitation concentration degree (PCD) and precipitation concentration period (PCP) of the Plateau are defined. By means of EOF and correlation, as well as spatial and temporal distributions of PCD and PCP, the relationship between PCD and plateau heavy rainfall, and signals of PCP are investigated. The results show that PCD of the plateau area is between 0.4 and 0.8, while PCP is within 36-41 pentads. In space scale, PCD is nearly congruous in the whole region, while PCP manifests a north-south reverse pattern mainly. In time scale, PCD appears to be a subdued tendency when PCP displays an advanced characteristic. Except for a few places in the southern plateau, PCD shows positive correlation with days as well as amounts of intensive rainfall on plateau. In addition, the water vapor transports have significant differences between northern and southern PCP of the plateau, the onset of Bay of Bengal monsoons may have an effect on PCP of the southern plateau.
  • Estimation of Actual Evapotranspiration and Its Component in the Upstream of Jinghe Basin
    ZHANG Shulan, YU Pengtao, WANG Yanhui, ZHANG Haijun, Valentina Krysanova, HUANG Shaochun, XIONGWei, XU Lihong
    2011, 66(3): 385-395. https://doi.org/10.11821/xb201103011
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    The ecohydrological model SWIM was used to simulate the hydrological process based on the data of vegetation, soil, climate, hydrology in the upstream of Jinghe River located at the Jingchuan station, and actual evapotranspiration and its components were estimated. The result showed that SWIM model was applicable to this area, and the average annual actual evapotranspiration (AET) was 443 mm from 1997 to 2003 in the watershed, with soil evaporation being 259 mm, vegetation transpiration 157 mm, and canopy interception 27 mm. In the watershed, the AET of the forest and non-forest area in rocky mountain was 484 mm in maximum and 418 mm in minimum respectively. And the AET of loess area was 447 mm lower than that of forest area and higher than that of non-forest area in rocky mountain. In addition, soil evaporation in forest area was significantly low, while the transpiration and canopy interception in the area were obviously high in the watershed. The inter-annual AET mainly occurred in the period from May to August, which was 60% of the total annual AET, with the great proportion 63% of canopy evapotanspiration. The AET of wet year increased by 78 mm compared with that of dry year, among which, soil evaporation increased greatest, followed by transpiration and canopy interception.
  • A Review on Uncertainty Analysis of Large-scale Hydrological Cycle Modeling System
    SONG Xiaomeng, ZHAN Chesheng, KONG Fanzhe, XIA Jun
    2011, 66(3): 396-406. https://doi.org/10.11821/xb201103012
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    The uncertainties in hydrological modelling come from four major sources: uncertainties in input data and parameters, uncertainties in model structure, uncertainties in analysis method and the initial and boundary conditions. Much attention has been paid to the uncertainty issues in hydrological modelling due to their great effects on prediction, and also many methods are applied to uncertainty quantification in the hydrological model. In this paper, we reviewed the recent advances on the uncertainty analysis approaches in the large-scale complex hydrological model, such as, large-scale hydrological system coupled with the land-atmosphere model. And then the PSUADE and its uncertainty quantification method were introduced, which will be a useful tool and platform for integration research in uncertainty analysis of large complex hydrological models.
  • Quantification of the Causes for Reference Crop Eapotranspiration Changes in Growing Season in Northwest China
    CAOWen, SHEN Shuanghe, DUAN Chunfeng
    2011, 66(3): 407-415. https://doi.org/10.11821/xb201103013
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    Based on the FAO-56 Penman-Monteith equation, the changes of reference crop evapotranspiration (ET0) were studied by analyzing the sensitivity coefficients of ET0 to air temperature, wind speed, relative humidity and shortwave radiation together with their relative changes in growing season in Northwest China using a 49-year dataset. The results show that the changes of ET0 are primarily attributed to wind and air temperature due to their significant trends. Shortwave radiation and relative humidity have negligible effects on ET0 for their insignificant trends. The positive contribution of temperature and the negative contribution of wind and solar radiation are observed in most regions, but the contribution of relative humidity is positive in eastern part and negative in western part. The consistence between the actual ET0 changes and the estimated ET0 changes calculated by the contribution of four meteorological variables indicates that the method based on sensitivity coefficients interpreted together with actual changes in variables to quantify the impact of each variable on the ET0 trend is reasonable.
  • Retrieving Individual Attributes from Aggregate Dataset for Urban Micro-simulation: A Preliminary Exploration
    LONG Ying, SHEN Zhenjiang, MAO Qizhi
    2011, 66(3): 416-426. https://doi.org/10.11821/xb201103014
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    As the traditional top-bottom based macro-simulation models can not properly adapt to the present research of spatiotemporal dynamic urban system, the bottom-up micro-simulation models using individual data have gradually become a novel perspective for investigating urban systems recently. However, one of the factors restraining the wide application of micro-simulation models is the limited individual data due to the difficulties of data fetching and processing. Such a situation is especially serious in China, where individual dataset is not available from the official census and can only be obtained via various surveys in small scale conducted by separate units. This paper proposes a new solution to retrieve individual dataset from aggregate dataset, e.g. statistical data, for urban micro-simulation under the current sparse-data environment. Based on the existing multi-resource official statistical data, non-official surveys, as well as general relationships among individual attributes, our approach can disaggregate the individual attributions and location obeying the input aggregation observations data. This approach has proved to be significantly accurate at the statistical level, and can be conveniently adopted for urban micro-simulation under the present statistical institutions of China.