The effect of management choices on the sustainability and economic performance of a mixed fishery: a simulation study     

Kraak  S. B. M.; Buisman  F. C.; Dickey-Collas  M.; Poos  J. J.; Pastoors  M. A.; Smit  J. G. P.; van Oostenbrugge  J. A. E.; Daan  N. 《ICES Journal of Marine Science》2008,65(4):697-712

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海浪破碎对海洋上混合层中湍能量收支的影响   总被引：2，自引：1，他引：2  

孙群  管长龙  宋金宝 《海洋与湖沼》2006,37(1):69-74

海浪破碎产生一向下输入的湍动能通量,在近海表处形成一湍流生成明显增加的次层,加强了海洋上混合层中的湍流垂向混合。为了研究海浪破碎对混合层中湍能量收支的影响,文中分析了海浪破碎对海洋上混合层中湍流生成的影响机制,采用垂向一维湍封闭混合模式,通过改变湍动能方程的上边界条件,引入了海浪破碎产生的湍动能通量,并分别对不同风速下海浪破碎的影响进行了数值研究,分析了混合层中湍能量收支的变化。当考虑海浪破碎影响时,近海表次层中的垂直扩散项和耗散项都有显著的增加,该次层中被耗散的湍动能占整个混合层中耗散的总的湍能量的92.0%,比无海浪破碎影响的结果增加了近1倍;由于平均流场切变减小,混合层中的湍流剪切生成减小了3.5%,形成一种存在于湍动能的耗散和垂直扩散之间的局部平衡关系。在该次层以下,局部平衡关系与壁层定律的结论一致,即湍动能的剪切生成与耗散相平衡。研究结果表明,海浪破碎在海表产生的湍动能通量影响了海洋上混合层中的各项湍能量收支间的局部平衡关系。  相似文献   

赤道行星波对西赤道太平洋暖池热传播的作用     

石强  许建平  朱伯康 《海洋学研究》2003,21(3):1-13

利用热带海洋和全球大气试验(TOGA)期间(1980～1996年)热带大气海洋观测阵(TAO)的长期浮标资料,分析了赤道行星波对西赤道太平洋暖池热传播的作用。结果表明,西赤道太平洋暖池纬向热传播主要出现在次表层水体中,并沿温跃层向东传播;而向西传播的季节热结构变化主要出现在中、西赤道太平洋的混合层中;驻波型传播在西赤道太平洋主要出现于温跃层,在中赤道太平洋主要出现于混合层和温跃层,在东赤道太平洋主要出现于混合层。在平均条件下,赤道太平洋上层水温纬向热传播信号以驻波型和东传型较强,西传型较弱。赤道Kelvin波压力分量贯穿西、东赤道太平洋并向东输送暖池热能,纬向流分量的热输送主要出现在西赤道太平洋;Rossby波压力分量的热输送主要出现在东、中赤道太平洋;混合Rossby重力波激发纬向流的热输送作用比相应温跃层扰动强。在平均条件下,赤道太平洋上层水温的驻波型变化制约了西赤道太平洋暖池热量的持续向东输送,因此形成了赤道太平洋水温的正常季节变化形态。当水温的驻波型变化减弱而东传型变化加强时,随后将形成厄尔尼诺现象。  相似文献   

Effect of River Discharge on Bay of Bengal Circulation   总被引：1，自引：1，他引：1  

Srinivas Chamarthi  P. Shree Ram  Lalita Josyula 《Marine Geodesy》2013,36(3):160-168

The seasonal circulation and mixed layer depths in Bay of Bengal is modeled using the three-dimensional Princeton Ocean Model (POM). Along the coastal boundaries a higher resolution is accomplished using the curvilinear orthogonal grid. Model uses a free-surface and terrain following sigma coordinates. The initial climatological salinity and temperature fields for the model are derived from the World Ocean Atlas-2001(WOA01). The Model is forced with wind stress derived from COADS wind climatology. Bilinear interpolation is used to obtain the initial fields and wind stress to the required model specification. Using the seasonal fields and wind stress the model is integrated for simulating Bay of Bengal circulation. The numerical simulations on climatological scale for monsoon months were conducted to study the evolution of dynamics. The simulations bring out not only the typical characteristic features of fresh water plume along the coast but also intensification of the flow over the monsoon period. The increase in the fresh water flow found to affect only the western parts of the BoB. The opposing currents due to monsoon winds and southward flowing fresh water discharge (FWD) were also delineated. The model results show that the wind stress induced turbulence process is subdued in the presence of strong vertical salinity stratification due to the influence of FWD. The simulated mixed layer depths are in agreement with the reported analytical energy required for mixing values.  相似文献   

像素级和对象级高分辨率遥感图像变化检测分析     

赖正文  夏小云 《测绘通报》2021,(2):59-63

高分辨率遥感图像具有丰富的纹理信息,而像素级变化检测方法主要分析图像的光谱信息,导致将像素级变化检测方法用于高分辨率遥感图像具有一定的局限性.因此,本文提出了一种像素级与对象级相结合的高分辨率遥感图像变化检测方法,解决了像素级与对象级变化检测方法中存在的椒盐现象、误检等问题.首先,结合高分辨率遥感图像的多维特征,构建遥...  相似文献   

北京市四环内街区尺度下的主题混合模式挖掘     

刘菁菁  刘雨思  伊迪升  杨静  张晶 《地球信息科学学报》2020,22(6):1370-1382

城市是多样性聚集的场所,且多元化和差异性日益增强,故探究土地混合利用具有一定的现实意义。现有的土地混合研究大多以POI（Point of Interest）为研究基础,着眼于城市主题的研究较少。本文采用百度POI数据,在街区尺度下考虑POI共现以提取主题,并挖掘北京市四环内的主题混合模式,其结果可以为城市规划及其建设提供参考。首先,采用LDA（Latent Dirichlet Allocation）主题模型得出街区的主题向量以及主题的POI共现模式;其次,引入多样性指数对街区的混合度进行度量,并依据自然断裂法将街区分为高混合街区、中等混合街区、低混合街区3类;最后,为了探究3类街区中的主题混合模式,先采用多元线性回归找出不同类街区中对混合度影响显著的主题,在此基础上对街区中的混合模式进行提取。结果表明：高混合街区的主题混合模式都是茶座餐厅主题与其他主题的混合;中等混合街区中的混合模式大多是以公司企业主题与住宅（商铺）主题再结合其他主题的混合;低混合街区中最典型的2种模式是茶座餐厅主题主导与风景名胜主题主导的接近单一的模式。不同的模式也体现了不同混合区的特征及其之间的差异,有助于对城市深度理解,从而为混合城市的建设提供参考。  相似文献   

Response of the upper ocean to tropical cyclone in the Northwest Pacific observed by gliders during fall 2018     

Zekai Ni  Jiancheng Yu  Xuekun Shang  Wenming Jin  Yeteng Luo  Philip A Vetter  Huichang Jiang  Liu Yu  Sumin Liu  Hongzhou Xu 《海洋学报(英文版)》2021,40(1):103-112

The evolution of thermohaline structure at the upper ocean during three tropical cyclones(TCs) in the Northwest Pacific was studied in this study based on successive observation by two new-style underwater gliders during fall 2018. These remote-controllable gliders with CTD sensor enabled us to explore high frequency responses of temperature, salinity, mixed and barrier layers in the upper ocean to severe TCs in this area. Results showed that three significant cooling-to-warming and stratification destructing-to-reconstructing processes at the mixed layer occurred during the lives of three TCs. The maximal cooling of SST all reached ≥0.5℃ although TCs with different intensities had different minimal distances to the observed area. Under potential impacts of solar radiation, tide and inertial motions, the mixed layer depth possessed significant high-frequency fluctuations during TC periods.In addition, barrier layers appeared and vanished quickly during TCs, accompanied with varied temperature inversion processes.  相似文献   

一种Matlab与C#混合编程实现测量平差程序的方法     

林敬娜  程钢  路晓明  张启华  刘玲玲 《测绘工程》2022,31(1):45-51

文中针对测量平差的繁杂性及用户对处理软件的易用性要求,结合Matlab与C#语言编程各自的优势,依据测量平差的基本原理与方法,采用Matlab与C#混合编程方法,设计并实现一套简单的测量平差系统软件,其中Matlab用以实现平差函数程序设计,C#则利用VS.net平台进行界面及输入输出功能实现。以一个具体水准网实例验证系统的可行性与简便性,体现Matlab与C#混合编程在测量平差应用中的优越性。  相似文献   

基于伪纯像元的精度评价策略及其应用     

徐肖  李娅婷  樊辉 《地球信息科学学报》2022,24(8):1617-1630

土地覆被是地球科学研究中的重要参量,评价土地覆被数据的制图精度是保障数据合理使用的前提。本文提出了一种基于伪纯像元的精度评价策略(伪纯像元策略),即当低空间分辨率栅格窗口内对应的高空间分辨率数据中优势类别(面积最大的地类)的占比高于伪纯像元纯度阈值(代表像元纯度,取值范围:35%～100%,步长为5%)时,以此栅格窗口为基准生成土地覆被类型为优势类别的伪纯像元用于精度评价。以澜沧江-湄公河(澜湄)流域为试验区,选择GlobeLand30为参考数据,并基于混淆矩阵精度评价方法对比分析了伪纯像元策略与重采样法(最近邻法和众数法)在CCI-LC(300 m)和MCD12Q1(500 m)2套全球土地覆被数据精度评价中的差异。结果表明:(1)伪纯像元策略在35%～100%纯度阈值下对CCI-LC和MCD12Q1在澜湄流域评价的精度分别为72.76%～55.26%和71.44%～45.41%,比重采样法评价的单一精度(众数法:71.21%和70.54%、最近邻法:71.48和69.87%)能更好地反映像元纯度对土地覆被数据精度的影响;(2) CCI-LC的总体精度高于MCD12Q1,且2套数据的...  相似文献   

A contact problem for a poroelastic halfspace containing an embedded inextensible membrane     

P. Samea  A.P.S. Selvadurai 《国际地质力学数值与分析法杂志》2020,44(16):2167-2188

The paper examines the axisymmetric problem of the indentation of a poroelastic halfspace that is reinforced with an inextensible permeable/impermeable membrane located at a finite depth by a rigid indenter. The constitutive behavior of the poroelastic halfspace is described by the three-dimensional theory of poroelasticity proposed by M.A. Biot. The contact conditions between the indenter and the poroelastic halfspace are varied to accommodate both adhesive/frictionless contact and impermeable/permeable conditions. The formulation of the mixed boundary value problems uses the stress function approaches applicable to semi-infinite domains. Successive applications of Laplace and Hankel integral transforms are used to reduce the mixed boundary value problems to sets of coupled Fredholm integral equations of the second kind. These integral equations are solved using numerical approaches, applicable both for the solution of the systems of coupled equations and for Laplace transform inversion, to examine the time-dependent displacement of the rigid indenter. The analytical-numerical estimates for the time-dependent displacements of the rigid indenter are compared with results obtained using a finite element approach.  相似文献