Seasonal variation of upper layer circulation in the northern part of the East/Japan Sea     

Taekyun Kim  Jong-Hwan Yoon 《Continental Shelf Research》2010

Seasonal variation of upper layer circulation in the northern part of the East/Japan Sea and its mechanism were investigated using empirical orthogonal function (EOF) analysis with satellite sea surface heights over the northern East/Japan Sea and a three-dimensional circulation model. The spatial structure and temporal variation of first EOF mode, which explains about 64% of the total variance, indicate that a large cyclonic circulation in the northern East/Japan Sea shows a semi-annual variation with maximum strength in summer and winter. According to numerical model result, the Liman Cold Current, accepted as a major current in the northern East/Japan Sea, is well mixed vertically by the winter monsoon and the current in the upper layer has a relatively deep structure, with a maximum westward speed of about 20 cm/s in winter. On the other hand, in summer the current has a stronger baroclinic structure of velocity than in winter. Numerical experiments showed that in summer the temporal variation of upper layer circulation is controlled by thermal forcing, such as sea surface heat flux and inflow of heat transport into the East/Japan Sea through the Korea/Tsushima Strait. Moreover, the cyclonic circulation in the upper layer of the northern East/Japan Sea is also generated and strengthened by the positive wind stress curl occupying most of the East/Japan Sea during the winter. The seasonal variation of each forcing that drives the circulation is responsible for the strength or weakness of the upper layer circulation in the northern East/Japan Sea. The contribution of each forcing to the seasonal variation of the upper layer circulation is examined through sensitivity experiments. According to these numerical experiments, the upper layer circulation in the northern East/Japan Sea is strengthened twice a year, in winter and summer, and this semi-annual variation is determined by a combination of wind (winter) and thermal (summer) forcing.  相似文献   

A comparison between manganese nodules and cobalt crust economics in a scenario of mutual exclusivity     

Simone Martino  Lindsay M. Parson 《Marine Policy》2012,36(3):790-800

The past 20 years have been characterised by limited interest in the economic viability of deep seabed mining with the exception of those mineral ores rich in precious metals such as polymetallic sulphides. This paper goes against the tide. After reviewing the most significant literature, it compares the economic feasibility of mining polymetallic manganese nodules and cobalt-rich ferromanganese crusts in a scenario of mutual exclusivity. It uses a new indicator, the cobalt-nickel price ratio, whose aim is to verify at what metal prices the net present value of the two mining projects equalises. Previous research has shown that the turning margin between manganese nodules and cobalt crusts is a cobalt price of $50/kg. The present paper revises this by showing that the choice between mining crust and nodules depends on fluctuations in the price of nickel. A Monte Carlo simulation proves that cobalt crust mining could be reasonably preferred to manganese nodules at cobalt prices of $40-60/kg if the price of nickel fell below $11/kg. Within this condition, investors would receive the minimum acceptable internal rate of return of 15%, which is at a level of risk closer to the land-based mining. However, when the price of nickel passes the $11/kg threshold, the equilibrium between the two ventures can be reached only at a cobalt price greater than $100/kg, causing cobalt crust to become uncompetitive. Finally, the paper, recognising that prices are not unique drivers, introduces legal, political, technological and environmental concerns to show that the final choice between the two mining ventures cannot be merely driven by economic issues.  相似文献   

2.5维复电阻率反演及其应用试验   总被引：1，自引：0，他引：1  

范翠松  李桐林  严加永 《地球物理学报》2012,55(12):4044-4050

自复电阻率法被提出以来,其区分矿与非矿方面的潜力就引起了人们的广泛关注,但反演问题一直没有得到较好的解决,已经严重影响和制约了该方法的应用和发展.对此,本文提出并实现了利用多个排列视电阻率和视相位数据的2.5维SIP联合反演方法.算法利用最小二乘原理构建了反演目标函数,为提高反演的稳定性,在反演方程中加入了Occam法的光滑模型约束.通过借助电场的偏导数形式,推导出了灵敏度矩阵的解析表达式,并应用互换定理对其进行精确求取.反演算法充分利用了电磁感应和激电效应中的异常信息,能够同时反演出二维地质断面上所有单元的四种复电阻率参数.最后,利用该反演程序对安徽某地区的SIP实测数据进行了反演成像,通过与已知钻井资料及CSAMT反演结果的对比分析表明,该反演算法具有良好的应用效果.  相似文献   

油井流动成像束状探测电磁场   总被引：2，自引：0，他引：2       下载免费PDF全文

蔡家铁  吴锡令  张阔 《地球物理学报》2015,58(1):289-297

为了克服油井流动成像电磁探测的"软场"效应,提高成像质量,本文从测量物理模型出发,采用在轴向上屏蔽和径向上聚焦的方法构建束状探测场,通过有限元仿真计算电势分布以及测量敏感场,发现轴向上屏蔽后的电势分布均匀平坦,从而探测电磁场可以简化为二维场;径向上聚焦后敏感区域主要集中在发射电极和接收电极之间的束状区域内,敏感场呈马鞍状,其中间敏感性明显加强.模拟流动实验测量结果表明,束状探测电磁场的测量信号较强,成像质量明显提高.  相似文献   

地面自动站资料质量控制方案及应用   总被引：14，自引：2，他引：12       下载免费PDF全文

陶士伟  仲跻芹  徐枝芳  郝民 《高原气象》2009,28(5):1202-1209

为满足精细、 短时天气预报的需求, 我国地面自动站（AWS）观测系统的建设日趋完善。AWS资料在数值预报系统中没得到充分使用的原因之一是AWS观测资料的特殊性及数值预报系统缺少有效针对AWS观测资料的质量控制(QC)方案。本文AWS QC方案在参考国际先进的AWS QC方案基础上, 根据我国地面自动站的特点和数值天气预报模式对地面资料应用的要求设计。其目的是解决AWS观测资料在数值预报中应用的质量问题。本方案采用多种质量控制技术, 其中包括台站气候极值检查、 要素间一致性检查、 时间一致性检查、 持续性检查、 背景场一致性检查、 空间一致性检查、 综合决策算法、 自动统计评估反馈技术。本文从检查方法对错误资料的敏感度和确定性进行理论分析表明, 该方案具有更强的敏感度和确定性。将该方案应用于北京地区2006年8月AWS实际观测资料检验, 结果表明, 该方案能有效地识别观测资料中存在明显错误的资料, 有效地为地面自动站资料在数值模式中的应用提供客观质量依据。  相似文献   

下垫面非均匀流域的幂指数TOPMODEL的模拟研究     

孙菽芬  邓慧平  王倩 《气候与环境研究》2014,19(6):735-742

利用取消流域土壤表层饱和导水率0K、土壤饱和导水率有效衰减系数m和地下水补给速率R为空间均匀假设的幂指数TOPMODEL,对流域水量平衡各分量进行敏感性研究试验,揭示空间非均匀性对幂指数TOPMODEL模拟结果的影响。从特定研究流域所得结果中可得的主要结论有:1)0K、m和R的空间变化对流域的逐日地表径流和基流以及逐日总径流有影响,针对设定的0K、m和R的空间变化,其中m的空间变化较明显地增加了逐日地表径流和洪峰流量。2)就设定的0K、m和R的空间变化而论,对流域多年平均年总径流以及蒸发模拟结果影响不大,但改变了径流在地表径流和基流之间的分配;其中R的空间变化影响最显著,m和0K的空间变化影响则较小。  相似文献   

应用奇异向量方法的适应性观测实例研究     

路秀娟  钟青  陈涛  吴晓京 《气象学报》2010,68(6):967-976

近年来,通过适应性观测技术来减小预报误差已成为国际上数值预报中的一项关键技术,然而实施适应性观测对减小预报误差的影响评估是一个需要深入讨论的问题。文中利用奇异向量方法以2007年3月4日东北地区暴风雪天气过程为研究对象,考察了预报误差对不同观测区域观测资料的敏感性,在确定能量范数的基础上,分析了奇异向量的水平分和特征和垂直分布特征,利用奇异向量的空间结构确定了敏感区域。通过伪逆初始扰动场作为分析误差,研究验证区域的预报误差对不同区域增加观测的敏感性,试验结果表明,在敏感区域内进行补充观测来改善分析误差,能够最有效地提高验证区域内的预报水平;而减小非敏感区域内的分析误差对减小预报误差的贡献相对较小。这些结果表明,利用奇异向量法定义敏感区进行适应性观测,能够和有限的观测资源和计算资源的条件下,最大程度地减小验证区域的预报误差,从而达到提高验证区域预报准确率的目的。  相似文献   

静力稳定度对大地形降水影响的数值模拟研究     

姚昊  潘晓滨  臧增亮  张凯 《气象与减灾研究》2009,32(2):20-26,F0003

利用ARPS模式,通过调节过大地形山脉的湿大气静力稳定度进行敏感性试验,研究了湿大气静力稳定度对大地形降水的影响。结果表明,湿大气静力稳定度的改变影响了地形重力波的形成、维持和传播机制。当静力稳定度偏小时,地形重力波容易破碎,得不到有效维持;当静力稳定度偏大时,地形重力波又不易形成;仅当静力稳定度达到适合的强度时,地形重力波才能得到有效维持和传播。此外,垂直上升速度分布、辐合辐散运动及水汽的凝结输送等是影响大地形降水强度及分布状况的重要因素。  相似文献   

Groundwater vulnerability assessment in shallow aquifer of Kathmandu Valley using GIS-based DRASTIC model   总被引：1，自引：0，他引：1  

Dhundi Raj Pathak  Akira Hiratsuka  Isao Awata  Luonan Chen 《Environmental Geology》2009,57(7):1569-1578

In this paper, groundwater aquifer vulnerability map has been developed by incorporating the major geological and hydro-geological factors that affect and control the groundwater contamination using GIS based DRASTIC model. This work demonstrates the potential of GIS to derive a map by overlying various spatially referenced digital data layers that portrays cumulative aquifer sensitivity ratings across the Kathmandu Valley, Nepal, providing a relative indication of groundwater vulnerability to contamination. In fact, the groundwater is the major natural resources in Kathmandu for drinking purpose. The decline in groundwater levels due to the over exploitation and thus extracted water from shallow aquifer has been contaminated by the infiltration of pollutants from polluted river and land surface is continuous and serious. As the demand for water for human and industrial use has escalated and at the same time, the engineering and environmental costs are much higher for new water supplies than maintaining the existing sources already in use. Management of groundwater source and protecting its quality is therefore essential to increase efficient use of existing water supplies. Aquifer vulnerability maps developed in this study are valuable tools for environmental planning and predictive groundwater management. Further, a sensitivity analysis has been performed to evaluate the influence of single parameters on aquifer vulnerability assessment such that some subjectivity can be reduced to some extent and then new weights have been computed for each DRASTIC parameters.  相似文献   

Modelling soil water dynamics in a forest ecosystem. II: Evaluation of spatial variation of soil profiles     

W. Bouten  J. V. Witter 《水文研究》1992,6(4):445-454

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