海雾生成过程中平流、湍流和辐射效应的数值试验   总被引：11，自引：0，他引：11  

胡瑞金  董克慧  周发琇 《海洋科学进展》2006,24(2):156-165

利用相对湿度方程,结合数值模式研究了在海雾生成过程中平流、湍流和辐射的效应。结果表明,海雾生成的主要“推动力”是长波辐射冷却,湍流冷却在低层主要发生在平流的初始阶段。随着时间的推移,湍流对低层大气很快变为起加热作用,不利于海雾的生成。湍流和辐射效应在低层大气中符号相反(仅在海雾生成的初始阶段符号相同),量级相同,在高层大气中湍流和辐射效应符号相同,但辐射效应占优势。湍流效应和辐射效应是影响海雾生成的主要因素,平流直接作用似乎不大。平流、湍流和辐射效应及其总效应均随时间推移而减小。另外,还初步研究了风速大小和海温高低对平流、湍流和辐射效应及海雾生成的影响。  相似文献   

Preliminary study on the dynamic mechanism of the deep equatorial jets     

Wu Dexing 《海洋学报(英文版)》1994,13(4):465-474

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考虑表皮效应的径向溶质迁移模型以及半解析解          下载免费PDF全文

文章  李旭 《地质科技通报》2020,39(1):60-66

径向示踪试验是一种非常有效的获取含水层弥散参数的试验方法,但传统径向示踪试验很少考虑抽水井附近的表皮效应(由于钻井施工工艺所导致抽水井附近一定区域水力性质发生变化).建立了考虑表皮效应的单井注入示踪试验模型,并利用Lapalce变换以及数值逆变换获得了该模型的半解析解.系统分析了表皮区域水力性质对示踪试验穿透曲线的影响规律.研究结果表明:表皮区域的弥散度越大,穿透曲线早期的浓度越高,且峰值越高;表皮孔隙度越大,穿透曲线早期浓度越低,后期浓度越高;此外,散度差异也会导致浓度分布曲线在表皮区域与含水层界面处发生突变.总之,表皮效应对径向溶质迁移产生了较大的影响,有必要将表皮效应考虑到径向示踪试验中去.  相似文献   

平直斜坡上破波带内质量输移流对污染物输移影响的数值研究     

任春平  梁荣荣  郁重  白玉川 《海洋学报(英文版)》2019,38(9):102-112

破波带内外都有质量输移流存在，其对破波带内污染物输移有怎样的影响，需要进一步深入研究。本文基于实验以及考虑质量输移流的对流扩散数学模型研究了平直斜坡上破波带内质量输移流对污染物输移影响。数学模型包括波浪模型、近岸流模型以及对流扩散模型。首先建立了破波带内污染物输移数学模型，其中波浪场基于波能守恒方程来计算，波导流场基于Longuet-Higgins提出的辐射应力模拟，污染物对流扩散方程中考虑了质量输移流的影响，并利用算例验证该数学模型。其次简要介绍了平直斜坡上破波带内污染物输移实验，并分析了污染物输移特性。连续投放污染物会形成污染带，本文分析了两种波况下不同时刻污染带与岸线夹角的变化，以及污染物在垂直岸线和沿岸线方向的输移速度，结果表明对两种波况来说在初始10-40s污染团向岸线方向输移速度分别约为0.05m/s、0.017m/s，之后速度分别减小为0.001m/s、0.011m/s。数值模拟结果与实验结果比较表明：考虑质量输移流的模拟结果与实验更为吻合。因而，通过实验以及数模研究表明破波带内质量输移流对破波带内污染物在垂直岸线方向的输移有重要影响，而对沿岸方向的输移则影响较小。  相似文献   

基于重叠网格方法浮筒涡激运动特性数值分析     

谢康迪  赵伟文  万德成 《海洋工程》2019,37(3):24-34

浮筒被广泛应用在海洋工程中,研究浮筒的涡激运动对于减少其对海洋平台构件的疲劳损坏具有指导意义。传统的动网格方法在处理浮筒转动运动时会因网格变形过大导致计算不收敛,采用了重叠网格方法以解决这一问题。数值试验采用了基于开源工具包Open FOAM自主开发的naoe-FOAM-SJTU求解器。分别进行了自由衰减数值试验和涡激运动数值试验。研究表明,随着折合速度的增加,浮筒的顺流向、横流向、垂荡和艏摇运动频率增加,且顺流向与垂荡频率相近,横流向与艏摇频率相近;其次,根据涡量场分布,表明浮筒前一时刻的泻涡会影响到浮筒之后时刻的周向涡量分布;最后,研究发现自由端对于浮筒尾流场泻涡有着显著影响,为将来探究减少浮筒涡激运动的方法提供指导。  相似文献   

The characteristics of sea fog with different airflow over the Huanghai Sea in boreal spring   总被引：2，自引：0，他引：2  

HUANG Jian  WANG Xin  ZHOU Wen  HUANG Huijun  WANG Dongxiao  ZHOU Faxiu 《海洋学报(英文版)》2010,29(4):3-12

Using the observations from ICOADS datasets and contemporaneous NCEP/NCAR reanalysis datasets during 1960-2002, the study classifies the airflows in favor of sea fog over the Huanghai (Yellow) Sea in boreal spring (April-May) with the method of trajectory analysis, and analyzes the changes of proportions of warm and cold sea fogs along different paths of airflow. According to the heat balance equation, we investigate the relationships between the marine meteorological conditions and the proportion of warm and cold sea fog along different airflow paths. The major results are summarized as follows. (1) Sea fogs over the Huanghai Sea in spring are not only warm fog but also cold fog. The proportion of warm fog only accounts for 44% in April, while increases as high as 57% in May. (2) Four primary airflow paths leading to spring sea fog are identified. They are originated from the northwest, east, southeast and southwest of the Huanghai Sea, respectively. The occurrence ratios of the warm sea fog along the east and southeast airflow paths are high of 55% and 70%, while these along the southwest and northwest airflow paths are merely 17.9% and 50%. (3) The key physical processes governing the warm/cold sea fog are heat advection transport, longwave radiation cooling at fog top, solar shortwave warming and latent heat flux between airsea interfaces. (4) The characteristics of sea fog along the four airflow paths relate closely to the conditions of water vapor advection, and the vertical distribution of relative humidity.  相似文献   

Ocean-atmosphere momentum coupling in the Kuroshio Extension observed from space     

W. Timothy Liu  Xiaosu Xie 《Journal of Oceanography》2008,64(4):631-637

Using a combination of Quick Scatterometer (QuikSCAT), Advanced Microwave Scanning Radiometer-Earth Observing System (AMSR-E), and Lagrangian drifter measurements, we demonstrate that wind data alone are not sufficient to derive ocean surface stress (momentum flux) over mid-latitude ocean fronts, specifically the Kuroshio Extension. There was no continuous and large-scale stress measurement over ocean until the launch of the scatterometers. Stress had been derived from winds through a drag coefficient, and our concept of stress distribution may be largely influenced by our knowledge of wind distribution. QuikSCAT reveals that the variability of stress could be very different from wind. The spatial coherence between the magnitude of stress and sea surface temperature (SST), between the divergence of surface stress and the downwind SST gradient, and between the vorticity of stress and crosswind SST gradient, are the inherent characteristics of stress (turbulence production by buoyancy) that would exist even under a uniform wind field. The coherence between stress vorticity and SST gradient is masked by the rotation of ocean currents over the Kuroshio meanders. Surface stress rotates in the opposite direction to surface currents because stress is the vector difference between wind and current. The results are in agreement with a previous study of the Agulhas Extension and confirm the unique stress measuring capability of the scatterometer.  相似文献   

A dynamic equation for the potential energy anomaly for analysing mixing and stratification in estuaries and coastal seas   总被引：5，自引：0，他引：5  

Hans Burchard  Richard Hofmeister 《Estuarine, Coastal and Shelf Science》2008,77(4):679-687

In this paper, a time-dependent dynamic equation for the potential energy anomaly, , is rigorously derived from dynamic equations for potential temperature and salinity, the continuity equation and the equation of state for sea water. The terms locally changing are (A) the -advection, (B) the depth-mean straining, (C) the non-mean straining, (D) the vertical advection, (E) the vertical mixing, (F) surface and bottom density fluxes, (G) inner sources of density e.g. due to absorption of solar radiation and the non-linearity of the equation of state, and (H) horizontal divergence of horizontal turbulent density fluxes. In order to derive the equation in concise form, a vertical velocity (linearly varying with depth) with respect to depth-proportional vertical coordinates had to be defined. The evaluation of the terms in the -equation is then carried out for a one-dimensional tidal straining study and a two-dimensional estuarine circulation study. Comparisons to empirical estimates for these terms are made for the one-dimensional study. It is concluded that the -equation provides a general reference for empirical bulk parameterisations of stratification and mixing processes in estuaries and coastal seas and that it is a tool for complete analysis of the relevant terms from numerical models.  相似文献   

热带太平洋盐度变化:2015?2017年盐度异常     

史荒原  杜凌  徐道欢 《海洋学报》2020,42(3):47-58

本文利用Argo海水盐度资料、海流同化数据和同期大气再分析数据，探讨热带太平洋盐度趋势变化和相关动力过程。Argo资料显示，2015?2017年热带太平洋出现显著的盐度异常(SAE)，这是改变长期趋势的主要原因，表现为表层显著淡化和次表层咸化特征。这种盐度异常具有明显的区域性特征和垂直结构的差异，体现在热带太平洋北部海区(NTP)和南太平洋辐合区(SPCZ)表层淡化，盐度最大变幅为0.71～0.92，淡化可以达到混合层底；热带太平洋南部海区(STP)次表层咸化，最大变幅为0.46，主要发生在温跃层附近，期间盐度异常沿着等位密面从西向东扩展。平流和挟卷是与SAE密切相关的海洋动力过程，两者在NTP淡化海域有着持续而较为显著的影响，在SPCZ淡化、STP咸化海域后期贡献也较大，其中盐度平流对热带太平洋海区盐度变化起主要贡献。NTP淡化海区表层淡水通量和STP咸化海区密度补偿引起的混合也是SAE的重要影响因素。  相似文献   

Advective flow in sediments under the influence of compaction     

EKKEHARD HOLZBECHER 《水文科学杂志》2013,58(4):641-649

Abstract

Models on flow and transport in surface water sediments currently neglect compaction, although it is well understood that compaction is one of the major processes below the free fluid-sediment interface. Porosity changes in the sediment layers, as a result of compaction, are measured in almost all probes: porosity decreases with the distance from the surface water-sediment interface. This paper provides a rigorous derivation of basic flux terms for a frame of reference that is moving with the fluid-sediment interface. It is shown how burial rate, interface velocity, velocities of fluid and solid phase and porosity are connected—under steady-state conditions. It turns out that porosity and the velocities in a one-dimensional column can be directly computed from each other. These findings are important not only for the understanding of compaction-driven flow itself; they are crucial for all studies on storage and transport of chemical components in sediments. As mass fluxes across the sediment-water interface may be affected, there is an indirect link on surface water quality, making these findings relevant also for research on eutrophication of surface water bodies and/or on biogeochemical cycles.  相似文献