Reducing horizontal diffusion errors in σ-coordinate coastal ocean models with a second-order Lagrangian-interpolation finite-difference scheme     

Wenrui Huang  Malcolm Spaulding 《Ocean Engineering》2002,29(5):495-512

When a steep bottom slope exists, it is well known that conventional methods for calculating horizontal diffusion in sigma-coordinate coastal ocean models causes spurious transport (e.g. salinity, temperature, and sediments) and currents. In this study, a second-order accurate finite-difference algorithm and program have been developed to reduce the spurious numerical diffusion errors. In the proposed algorithm, the finite differencing is performed in the x-z coordinate system to approximate the horizontal gradient. Each variable in the finite differential formation is calculated in the sigma-coordinate grid cells using a second-order Lagrangian interpolation polynomial. In conjunction with a stepwise bottom boundary condition, numerical experiments show that the proposed finite-difference scheme considerably reduces numerical errors compared to conventional approaches when dealing with horizontal diffusion over steep topography, which often occurs in coastal oceans and navigation channels.  相似文献   

Hydrodynamic modeling and ecohydrological analysis of river inflow effects on Apalachicola Bay,Florida, USA     

Wenrui Huang 《Estuarine, Coastal and Shelf Science》2010,86(3):526-534

This paper presents an integrated hydrodynamic modeling and probability analysis approach to assess the long-term effects of changing river inflows on the estuarine ecosystem. The probability analysis method, which is popularly used in advanced hydrological frequency analysis of river flows and rainfalls, has been applied to analyze the effects of changing inflow on salinity and thus on oyster ecology in Apalachicola Bay. Long-term salinity data were predicted through the application of a calibrated 3D hydrodynamic model under two river inflow conditions over a 10-year period. The first flow represents the historic flow. The 2nd flow condition, called Scenario-1, represents a regulated flow scenario to account for the potential increasing upstream water demands. Two stations, Mid Bay and Dry Bar, in the bay were selected to examine the estuarine responses. Under the historic flow condition, the maximum probability salinity at Dry Bar in the rich oyster reef is near 24 ppt, within the optimal salinity range for oyster growth of 16–26 ppt (Harned et al., 1996); the maximum probability salinity at Mid Bay station is 27 ppt, beyond the optimal salinity for oyster growth in mid-bay area where there is no oyster reef around. While it is difficult to examine the difference between two scenarios by conventional time series analysis of river flows and salinity, probability analysis reasonably characterizes and quantifies the changes of river flow and salinity patterns over the 10-year period. The Scenario-1 has caused the increase of the probability in low flows. Higher probability of low flows for the regulated flow scenario shortens the period of optimal salinity in the oyster reef, and cause substantial increase of exceedance probability of higher salinity in the oyster reef to the level beyond the optimal salinity range for oyster growth. The probability analysis approach has demonstrated its advantage for the risk assessments of the long-term estuarine ecohydrological effects under various regulated inflow scenarios to support estuarine water resources managements.  相似文献   

结合小波包变换和随机森林的ASTER蚀变信息提取     

唐淑兰  曹建农  王国强  卜涛 《地质学报》2021,95(3):924-933

为了更准确地提取蚀变信息,本文选择新疆、甘肃和内蒙古三省交界部位为研究区,结合小波包变换和随机森林提取ASTER蚀变信息。首先,选择主要蚀变类型的诊断性波段进行特征向量主成分分析,得到主分量影像;接着,对主分量影像进行小波包变换,使用代价函数选择最优小波包树,并提取高低频信息构造分类向量;然后,经过特征筛选构造随机森林分类模型,并提取矿化蚀变信息;最后,通过野外采样、薄片鉴定对提取结果进行精度评价。铁染、Al-OH及Mg-OH蚀变信息的主成分分析波段组合分别选择Band 1、2、3、4,Band 1、3、4、6及Band 1、5、8、9。结果表明,本文方法提取铁染、Al-OH基团及Mg-OH基团蚀变信息的总体精度可达到88.7443、85.5469及91.7594,Kappa分别为0.7767、0.6732及0.8362,与成矿区带及已有的该区域的成矿特征相关性较好。本研究采用的最优小波包树能充分利用矿物光谱的能量特征,随机森林可削弱矿物组分的噪声干扰,研究结果可为遥感蚀变信息提取提供技术参考。  相似文献   

利用纹理特征的SAR与光学图像融合方法研究     

卜丽静  吴畅  何志博  张正鹏 《测绘工程》2015,(5):5-10

针对SAR与光学图像的融合问题,提出一种基于SAR图像中纹理特征的Contourlet变换融合方法。利用灰度共生矩阵法提取SAR图像的纹理特征,分析各个纹理特征间的相关性,得到重要纹理特征图。用HSV变换提取光学图像的强度分量。将重要纹理特征和强度分量利用改进的Contourlet多尺度变换融合,得到新的强度分量。通过HSV逆变换得到SAR与光学的融合图像。利用Landsat8和Cosmo-SkyMed图像进行融合实验,并与小波、HSV、Brovey、Contourlet变换融合方法对比分析,实验表明该方法能够较好的保持光学图像的光谱特征和SAR图像的纹理、强散射特征,增加图像细节信息,提高图像可解译性。  相似文献   

鄂尔多斯盆地大牛地气田储集层物源分析   总被引：1，自引：0，他引：1  

谭晨曦  李文厚  冯娟萍  曾明  卜颖 《矿物学报》2010,30(3)

晚古生代太原组-下石盒子组地层是鄂尔多斯盆地大牛地气田重要的储集层位,依据大量分析测试数据,从砂岩碎屑矿物成分、轻重矿物组合、石英阴极发光、REE地球化学以及沉积相和岩相古地理等方面对该地区太原组-下石盒子组的物源进行了综合研究。结果表明,大牛地气田储集层物源区主要为具活动性特征的再旋回造山物源区,物源方向较为稳定,明显受到北部物源的控制,其母岩应来源于盆地北部阴山古陆前寒武系古老的变质岩岩系。  相似文献   

双谱估计法在海底钴结壳微地形探测中的应用     

周知进  罗柏文  卜英勇 《物探与化探》2010,34(3)

海洋环境中水下超声测量系统往往因环境中机械噪声、背景噪声以及混响等强噪声而导致测距精度低,因而具有一定局限性。双谱的时延估计方法对高斯噪声具有屏蔽能力,能更好地压制噪声,并准确估计信号的时间延迟,且双谱功率谱重构要比直接用FFT变换方法估计功率谱具有更好的性能。利用双谱估计对背景噪声不敏感的特性来处理超声回波信号,根据实验室水池实测数据,验证了该方法的适用性。研究结果表明:在先验知识较少和背景噪声较强时双谱法比广义互相关法的适用性更好。  相似文献   

内蒙古阿拉善南部地区富Cr、Ni斜长花岗岩体的发现及其地质意义          下载免费PDF全文

卜文瑞  王廷印 《地质论评》2001,47(1):108

内蒙古自治区阿拉善南部地区富Cr、Ni的斜长花岗岩体以岩基产出。代表性岩体有阿斗青—当山斜长花岗岩体和红敖包斜长花岗岩体。前者出露面积为658km~2,侵入于太古宇下阿拉善群上部岩系(Arxl~2)和古元古界上阿拉善群(Pt_1sl),被Sm-Nd等时线年龄为773.1±10.8 Ma的变质辉长岩侵入破坏(陶仙聪等,1994);后者出露面积为393km~2,侵入前震旦系,被后期岩体侵入,并被上侏罗统和下白尘统不整合覆盖。  相似文献   

SSZ-1型双管双簧海底振动取心钻具          下载免费PDF全文

补家武  鄢泰宁周蒂　陈汉中 《探矿工程》2001,(1):19-20

针对海底振动取样的一些特殊情况,介绍了自行研制的适用于海底振动取样的SSZ－1型双管双簧取心钻具，分析了其结构原理及对海底取的适应性。  相似文献   

中国西部生态经济走廊综合开发的战略转变   总被引：2，自引：3，他引：2  

方创琳  步伟娜 《干旱区地理》2004,27(4):455-464

河西走廊是一条事关国家和地区生态安全及经济安全的具有战略意义的生态经济走廊和旅游走廊，是我国西部大开发战略重点区域“两带一区”的重要组成部分，是我国西部建设的唯一一个实体型生态经济走廊。建设好这条生态经济走廊，需要实现经济综合开发的10大战略转变。即：由“古丝绸之路走廊”转变为“新欧亚大陆桥走廊”，由开发移民走廊转变为生态移民走廊，由粮食走廊转变为肉食走廊、制种走廊和草业走廊，由单一工矿走廊转变为综合型生态工业走廊，由串珠状城镇走廊转变为生态城市走廊，由缺水走廊转变为生态节水走廊，由生态脆弱走廊转变为“生态重建走廊”，由战争要道走廊转变为战略要冲走廊，由“多病的生存经济走廊”转变为“健康的生态经济走廊”。通过上述战略转变，重振丝路雄风，把河西走廊建设成科技型、节水型、外向型、加工型和生态型的健康生态经济长廊。  相似文献   

青海南部治多-杂多-带下石炭统杂多群   总被引：1，自引：0，他引：1  

牛志军段其发  王建雄白云山 涂兵卜建军  赵小明 《地层学杂志》2005,29(11):490-499

在青海南部治多-杂多-带1／25万地质填图中，对杂多群进行了重新划分，自下而上分为下碳酸盐岩组、碎屑岩组和上碳酸盐岩组。下碳酸盐岩组为深灰色中层状生物屑灰岩、鲡粒灰岩夹泥岩、细粒石英砂岩，属于台地边缘浅滩相；碎屑岩组为灰色中层状细粒石英砂岩、泥岩夹灰岩、玄武岩，属于三角洲相、陆棚相和台地边缘浅滩相；上碳酸盐岩组为灰色中厚层状生物屑灰岩，见燧石结核和条带，为陆棚相和台地相沉积。丰富的筵类、非筵有孔虫、珊瑚化石，表明杂多群地质时代为早石炭世大塘期-德坞期。根据岩性组合、生物群面貌杂多群与青海南部杂多-囊谦地区杂多群、西藏东部昌都地区马查拉群可很好地对比。  相似文献