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张晶  刘琦 《大地测量与地球动力学》2010,30(6):6-9

?????й??????????????硰??塱?????????????С????????????????????????????峱?????????????????????????????λ??????????????????λ???????????????????????????峱????????仯????????????????????????????????к????????????????????????????8.0??????6.1?????6.0???????????????????????????????????????1???????????????????仨????????????????????????????????????  相似文献   

Critical perspectives on the evaluation and optimization of complex numerical models of estuary hydrodynamics and sediment dynamics     

J.R. French 《地球表面变化过程与地形》2010,35(2):174-189

Numerical hydrodynamic and sediment transport models provide a means of extending inferences from direct observation and for advancing our understanding of estuarine processes. However, their parametric complexity invites questions concerning the extent to which model output can be assessed with respect to data. This paper examines the basis for evaluating the performance of complex hydrodynamic and sediment transport models, with reference to a case study of a muddy meso‐tidal estuary. Sophisticated and computationally‐intensive models should be evaluated using robust objective functions, but conventional measures of fit and model efficiency invoke restrictive assumptions about the nature of the errors. Furthermore, they offer little insight into causes of poor performance. Optimization of tidal hydrodynamic models can usefully combine conventional performance measures with harmonic analysis of modelled shallow water tidal constituents that are diagnostic of the interactions between tidal propagation, bathymetry and bottom friction. Models with similar efficiencies can thus be distinguished and likely sources of error pinpointed. Hydrodynamic models have a predictive power that is rooted in a more‐or‐less complete representation of the physical processes and boundary conditions that are well‐constrained with respect to data. In contrast, fine sediment models rely on a less complete conceptualization of a broader set of processes and, crucially, have a parametric complexity that is unmatched by the quantity and quality of observational data. Their performance as measured by conventional objective functions is weaker and it is important to match the structural complexity of model errors with analyses that can localize the scales and times of poor performance. Wavelet analysis is potentially useful here as a means of identifying aspects of the model that need improvement. The context in which such models are deployed is also important. Used heuristically, what might otherwise be dismissed as weak models can still provide mechanistic support for empirically‐derived inferences concerning specific aspects of system behaviour. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   

Tide‐modulated hyperpycnal flows off the Huanghe (Yellow River) mouth,China     

Houjie Wang  Naishuang Bi  Yan Wang  Yoshiki Saito  Zuosheng Yang 《地球表面变化过程与地形》2010,35(11):1315-1329

Few hyperpycnal flows have ever been observed in marine environments although they are believed to play a critical role in sediment dispersal within estuarine and deltaic depositional systems. The paper describes hyperpycnal flows observed in situ off the Huanghe (Yellow River) mouth, their relationship to tidal cycles, and the mechanisms that drive them. Simultaneous observations at six mooring stations during a cruise off the Huanghe mouth in the flood season of 1995 suggest that hyperpycnal flows observed at the river mouth are initiated by high concentrations of sediment input from river and modulated by tides. Hyperpycnal flows started near the end of ebb tides, when near‐bottom suspended sediment concentration (SSC) increased rapidly and salinity decreased drastically (an inverse salt wedge). The median grain size of suspended particles within the hyperpycnal layer increased, causing strong stratification of the suspended sediments in the water column. Towards the end of flood tides, the hyperpycnal flow attenuated due to frictions at the upper and lower boundaries of the flow and tidal mixing, which collapsed the stratification of the water column. Both sediment concentration and median grain size of suspended particles within the bottom layer significantly decreased. The coarser sediment particles were deposited and the hyperpycnal flows stopped. The intra‐tidal behaviors of hyperpycnal flows are closely associated with the variations of SSC, salinity, and stratification of the water column. As nearly 90% of riverine sediment is delivered to the sea during the flood seasons when hyperpycnal flows are active, hyperpycnal flows at the Huanghe mouth and the river's high sediment loads have caused rapid accretion of the Huanghe delta. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

近期长江北支口门圆陀角附近潮滩地貌动态变化   总被引：2，自引：0，他引：2  

张振克  谢丽  丛宁  李瑛  王秀玲  何华春 《地理研究》2010,29(5):909-916

圆陀角位于长江北支岸线与江苏海岸线的交会处,独特的互花米草潮滩、淤泥质光滩环境和复杂的河海沉积动力,决定了潮滩地貌对海洋环境变化的响应具有敏感性。由于大规模的围垦,圆陀角附近过去40年来海岸线向东推进了6km。根据2006年以来多次的野外调查和室内粒度与钻孔岩芯的¹³⁷Cs分析, 2006年以来圆陀角附近潮滩淤积明显加强,由¹³⁷Cs时标估算的互花米草滩多年平均沉积速率为2.3cm/a, 2006~2008年观测到的互花米草滩淤积速率>4cm/a,粉砂淤泥质光滩的淤积速率更高;圆陀角风景区内互花米草滩前缘陡坎在风暴潮影响下侵蚀后退,并因粉砂淤泥质光滩的快速淤长而消亡,圆陀角附近潮滩地貌动态是对人类围垦活动、风暴潮与潮汐海洋动力的综合响应,互花米草与光滩快速淤积是近期圆陀角附近潮滩地貌演化的主要特点。  相似文献   

长江口崇明东滩不同植被带沉积速率研究   总被引：1，自引：0，他引：1  

姜亦飞  杜金洲  张敬  张文祥  张经 《海洋学报》2012,34(2):114-121

利用2007年丰水期、枯水期在崇明东滩芦苇带、藨草带和光滩采集的6根沉积物柱状样,研究了沉积物的粒度特征和过剩的210Pb和228Th及7Be活度的垂向分布特征,探讨了由陆地向海洋不同植被间的沉积物粒度变化规律。依据恒定比活度沉积速率模型,估算了不同时间尺度的崇明东滩芦苇带、藨草带和光滩的表观沉积速率。结果表明:3种核素示踪的崇明东滩的表观沉积速率都随潮滩植被的不同从陆到海方向逐渐降低,同时依过剩的210Pb和228Th,7Be的次序而增大。由过剩的210Pb和228Th计算的夏季沉积速率比冬季的稍高,而由7Be计算的夏季表观沉积速率则明显高于冬季的。结合沉积物粒度的时空分布和这些核素的大气通量,对利用这些核素测定潮滩沉积速率的影响因素进行了探讨。  相似文献   

长江河口北支上口不规则周期潮流的动力机制   总被引：1，自引：1，他引：0  

裘诚  朱建荣 《海洋学报》2012,34(5):20-30

数值模拟和动量分析长江河口北支上口枯季大潮期间 1 d内出现"四涨四落"不规则周期涨落潮流现象。长江河口北支上口 1日内两次涨潮流和两次落潮流为常规涨落潮流,受外海半日潮流控制,两次涨潮流和落潮流为非常规涨落潮流。北支上口非常规的涨潮流处于南支落潮的末期,范围小,流速弱,历时约2 h;表层主要是垂向黏滞项和水平扩散项与正压项间的作用,南向的垂向黏滞项起着决定的作用,底层则是斜压项与正压项间的作用;北支上口非常规涨潮流是北风、盐度锋面产生的南向斜压压强梯度力和南支末期落潮流的牵引作用共同造成的;径流抑制非常规涨潮流的产生,持续时间随径流量的增加呈指数递减,当径流量达到22 300 m3/s时,非常规涨潮流现象消失。北支上口非常规落潮流处于南支涨潮流的初期,由于在北支上口南支的涨潮流早于北支涨潮流,导致南支水体进入北支,形成北支上口第二次落潮流,范围较大,流速较强,历时约2.5 h,从表层至底层主要是垂向黏滞项与非线性平流项和正压项之间的作用。本文揭示了北支上口 1 d内出现"四涨四落"不规则周期涨落潮流的动力过程和机制。  相似文献   

董家口海域水动力环境分析     

赵迎春  王海棠  王海荣 《海洋科学》2012,36(8):104-108

根据2008年12月董家口港附近海域4个站位的实测海流资料,初步分析了研究海域的潮流场特征,同时采用数值模拟的方法对整个海区的水动力环境进行了分析,对进一步了解该海域的水动力环境具有积极的意义,为董家口港近岸海域的环境保护提供了科学依据.  相似文献   

基于余水位订正的海洋潮位推算关键技术研究          下载免费PDF全文

刘雷  李宝森  李冬  王冬  韩奇 《海洋测绘》2012,(2):11-14

从分潮数目选择、调和常数稳定性优化两个关键环节入手,选择11个主要分潮用于潮位推算,并利用邻近长期站对中短期验潮站调和常数做差比订正,显著提高了中短期验潮站的潮位推算精度。  相似文献   

水利工程影响下双台子河上溯潮水分流比的研究     

张嫣然  林国庆 《中国海洋大学学报(自然科学版)》2012,(10):106-110

盘锦双台子河口湿地拥有亚洲面积最大的芦苇种植区,但随着工农业用水增多,加之气候干旱和降雨偏少,苇田灌溉得不到保证。为了更好地解决双台子河流域苇田灌溉用水不足的问题,本文利用实测水位和流量等资料,基于Mike11建立了双台子河口的水动力学模型,并使用2008和2009年的实测潮位资料对模型进行了率定和验证,拟合精度较高,表明所建模型能反映河口区的水动力特征。通过设置水工建筑物的不同运行方式,模拟了上溯潮水分流到支流绕阳河与双台子河上游的流量比值。结果表明,水闸和橡胶坝对于研究区域内上溯潮水的分流比影响较大,在现状基础上橡胶坝建成之后能将绕阳河的分流比提高约50%,同时下游河口上溯潮水会减少20%～30%,但分流比对橡胶坝高度的变化并不敏感。不同调水方案以及水泵提水对分流影响甚微。  相似文献   

海南新海夏季潮流谱分析和余流研究     

严金辉  王道儒  侍茂崇  陈波 《海洋学报(英文版)》2012,31(4):21-26

根据夏季琼州海峡新海附近15 m处地层潮流谱分析结果可得,无论是f>0 或f<0,全日潮谱峰都高于半日潮谱峰。其中,半日潮周期,约为12 h,12.4 h,日潮存在两个,一个在23.9 h,另一个在25.8 h前后;在半日潮和全日潮分量中,反时针分量是主要的、顺时针的日潮能谱只有反时针的84%;顺时针的半日潮能谱只有反时针的63%;浅水分潮8.3 h,6.2 h和超过24 h的4.2 d,3 d等也很明显,但是未通过显著性检验; 大多数余流流速在5~10 cm/s之间,个别情况超过40 cm/s。受反时针运动涡旋影响,余流主要向偏东北、北、西北方向运动。在这个区间内的流向,占总观测数68%以上;风对余流也有重要影响:东北风将使余流方向偏向西北,偏北向风将使余流方向偏南。  相似文献