绿色海堤的沉积地貌与生态系统动力学原理: 研究综述*     

高抒  贾建军  于谦 《热带海洋学报》2022,41(4):1-19

绿色海堤是传统结构工程与海岸生态系统共同组合而成的新型海堤, 用以应对未来海面上升、风暴加剧给低地海岸防护带来的挑战。需解决的问题主要有海岸生态系统消浪过程及生态系统在海堤体系中的配置方式。理论分析、现场观测、物模数模所获结果表明, 海岸生态系统确有显著的消浪功能: 1) 陆架泥区消浪, 其机制以再悬浮和浮泥运动为主, 底部摩擦为次; 2) 潮滩下部的粉砂细砂滩底部摩擦和推移质运动共同造成波能耗散, 而上部的泥滩则以再悬浮和悬沙输运为主; 3) 在盐沼、红树林、海草床等由植被构成的生态系统, 植物通过形态阻力、茎秆运动来阻滞水流、耗散波能, 其效能高于沉积物床面对波能的耗散; 4) 生物礁主要有珊瑚礁和牡蛎礁, 其消能作用主要通过床面摩擦和波浪破碎, 效能较高, 尤其是在风暴期间。生态系统如何成为海堤的有机组成部分, 尤其是侵蚀型海岸的生态位修复和绿色海堤整体设计, 还需进一步研究相关的科学问题: 与硬质工程结合的盐沼-牡蛎礁的适应性生物学; 未来环境变化条件下生态系统的稳定性; 绿色海堤生态系统空间配置及其与风暴事件的时间尺度匹配; 基于均衡剖面理论的海堤形态优化。  相似文献   

南海北部陆架区内波的演变与耗散机制          下载免费PDF全文

刘志宇  白晓林  马家骏 《海洋科学进展》2022,40(4):791-799

海洋是多尺度强迫-耗散系统,机械能主要在大尺度输入,在小尺度耗散。在大、中尺度运动的能量向小尺度湍流传递过程中,内波扮演着重要角色。内波的生成和破碎可打破海洋动力平衡,而在陆架区,内波（主要是内孤立波）的浅化演变与耗散则是驱动湍流混合的关键过程。通过长期的理论、观测与数值模拟研究,目前已认识到内波浅化过程中主要发生如下演变：波形调制、极性转变、裂变、破碎与耗散。相较于直接发生破碎,浅化演变过程中的裂变及其引发的剪切不稳定和对流不稳定是内孤立波在陆架区的主要耗散机制,显著调制陆架区的跃层混合。从能量串级的角度讲,内孤立波浅化裂变为动力不稳定的高频内波是潮能串级的重要通道。本文简要回顾南海北部陆架区内波的研究历史,并着重总结内波在陆架区演变与耗散机制的研究进展。  相似文献   

Verification of significant wave representation method     

Winyu Rattanapitikon   《Ocean Engineering》2008,35(11-12):1259-1270

The significant wave representation method is the simplest method for computing the transformation of significant wave height across-shore. However, many engineers are reluctant to use this method because many researchers have pointed out that the method possibly contains a large estimation error. Nevertheless, Rattanapitikon et al. [Rattanapitikon, W., Karunchintadit, R., Shibayama, T., 2003. Irregular wave height transformation using representative wave approach. Coastal Engineering Journal, JSCE 45(3), 489–510.] showed that the wave representation method could be used to compute the transformation of root mean square wave heights. It may also be possible to use it for computing the significant wave height transformation. Therefore, this study was carried out to examine the possibility of simulating significant wave height transformation across-shore by using the significant wave representation method. Laboratory data from small- and large-scale wave flumes were used to calibrate and examine the models. Six regular wave models were applied directly to irregular waves by using the significant wave height and spectral peak period. The examination showed that three regular wave models (with new coefficients) could be used to compute the significant wave height transformation with very good accuracy. On the strength of both accuracy and simplicity of the three models, a suitable model is recommended for computing the significant wave height transformation. The suitable model was also modified for better predictions. The modified model (with different coefficients) can be used to compute either regular wave height or significant wave height transformation across-shore.  相似文献   

Energy of a Stringy Charged Black Hole in the Teleparallel Gravity     

Mustafa Saltı 《Astrophysics and Space Science》2006,306(4):201-204

We use the teleparallel geometry analog of the Møller energy-momentum complex to calculate the energy distribution (due to matter plus field including gravity) of a charged black hole solution in heterotic string theory. We find the same energy distribution as obtained by Gad who investigated the same problem by using the Møller energy-momentum complex in general relativity. The total energy depends on the black hole mass M and charge Q. The energy obtained is also independent of the teleparallel dimensionless coupling constant, which means that it is valid not only in the teleparallel equivalent of general relativity, but also in any teleparallel model. Furthermore, our results also sustains (a) the importance of the energy-momentum definitions in the evaluation of the energy distribution of a given spacetime and (b) the viewpoint of Lessner that the Møller energy-momentum complex is a powerful concept of energy and momentum.  相似文献   

全球纬向平均的海气耦合一维模式分析     

唐佑民 《成都信息工程学院学报》1991,(1)

本文从能量平衡角度,考虑海气相互作用和纬向间的差异,设计了一个纬向平均的海气耦合一维模式,进行了模式平衡态求解、敏感性试验以及随机分析。并对模式部分计算结果进行了与实测资料的比较,验证了模式的合理性和可信性。  相似文献   

A COMBINED REFRACTION-DIFFRACTION-DISSIPATION MODEL OF WAVE PROPAGATION   总被引：7，自引：0，他引：7  

楼菁 《中国海洋湖沼学报》1994,12(4):361-371

A numerical model based on the mild-slope equation of water wave propagation over complicated bathymetry,taking into account the combined effects of refraction,diffraction and dissipation due to wavebreaking is presented.Wave breaking is simulated by modifying the wave height probability density func-tion and the wave energy dissipation mechanism is parameterized according to that of the hydraulic jumpformulation.Solutions of the wave height,phase function,and the wave direction at every grid point areobtained by finite difference approximation of the governing equations,using Gauss-Seidel Iterative Method(GSIM)row by row.Its computational convenience allows it to be applied to large coast regions tostudy the wave transformation problem.Several case studies have been made and the results compare verywell with the experiment data and other model solutions.The capability and utility of the model forreal coast areas are illustrated by application to a shallow bay of northeast Australia.  相似文献   

Future goals for imaging     

A. J. Dean 《Experimental Astronomy》1995,6(4):77-84

The demands imposed on the imaging system of an astronomical gamma-ray telescope are numerous; it must identify and resolve individual point sources, often in crowded regions of the sky; extended emission structures must be measured on angular dimensions which can extend up to the size scale of the Galactic plane; it must achieve these goals with high sensitivity for both the wide band continuum radiation as well a for discrete spectral line emissions, and ideally have as large a field of view as possible to enhance the probability of registering the unpredictable transient events which pervade the high energy sky. True imaging systems are currently under development for operation for energies up to about 100 keV, however the most practical tool for higher energies, for the time being, remains the coded mask. Some options are briefly reviewed.  相似文献   

“95.8”川西大暴雨成因分析     

顾清源  康岚  张毅 《成都信息工程学院学报》1997,(2)

通过对“９５．８”大暴雨过程的全面技术总结，揭示了多种尺度系统间相互作用对产生大暴雨过程的贡献，并指出了云团的发生及其发展源于北方冷空气和南方低空急流持续影响所形成的两个中间尺度垂直环流。  相似文献   

Transient phenomena in the energetic behind-the-limb solar flare of september 29, 1989     

A. Bhatnagar  R. M. Jain  J. T. Burkepile  I. M. Chertok  A. Magun  H. Urbarz  P. Zlobec 《Astrophysics and Space Science》1996,243(1):209-213

The powerful cosmic ray flare of Sept. 29, 1989 occurred behind the limb and was observed over a wide spectral range. The analysis of optical, radio, and other relevant data suggest two phases of energy release. After an impulsive phase a prolonged post eruption energy release occurred in an extended region of the corona following the eruption of a large coronal mass ejection (CME). This phase is responsible for numerous coronal and interplanetary phenomena including the ground-level increase of cosmic rays.  相似文献   

关于业务上应用条件对称不稳定相关问题的讨论   总被引：1，自引：0，他引：1  

章丽娜  周小刚  夏扬 《气象学报》2018,76(5):824-832

条件对称不稳定（CSI）理论常常被用来作为倾斜对流的发展机制之一,在业务上常用来解释与锋面相联系的一条或多条中尺度雨带、雷达图像上观测到的带状雨带的成因等。条件对称不稳定的诊断包括CSI斜率判据、斜升对流有效位能（SCAPE）、湿对称不稳定（MSI）、相当位涡（EPV）等判据。业务预报人员存疑较多的问题是这些方法是否具有一致性并在业务上如何使用。针对上述问题,首先通过与业务预报人员较熟悉的条件不稳定类型作类比,来说明条件对称不稳定两种判据与条件不稳定两种判据的相似性。但在业务使用上,判别条件对称不稳定时多使用CSI斜率判据,即等动量面的坡度大于等位温面坡度而小于等湿球位温面坡度。由于条件对称不稳定通常出现在大气处于几乎饱和的情况下,此时的CSI斜率判据则演变为湿对称不稳定判据,即等动量面坡度小于等湿球位温面坡度。为判别相当位涡与湿对称不稳定判据是否具有一致性,文中的推导和实例分析均表明,二维相当位涡实际上是湿对称不稳定判据的另一种表现形式,但是湿对称不稳定判据需主观去比较等相当位温面与等动量面斜率大小,而二维相当位涡则可通过其是否小于0进行客观判断。需注意的是,在与推导条件对称不稳定斜率判据相同的二维坐标下,相当位涡与湿对称不稳定判据才具有一致性,将相当位涡扩展到常规坐标下使用三维相当位涡作为湿对称不稳定判据是不可取的。   相似文献