Drag Coefficient,Dynamic Roughness and Reference Wind Speed     

Paul?A.?HwangEmail author 《Journal of Oceanography》2005,61(3):399-413

Surface waves are the roughness element of the ocean surface. The parameterization of the drag coefficient of the ocean surface is simplified by referencing to wind speed at an elevation proportional to the characteristic wavelength. The dynamic roughness is analytically related to the drag coefficient. Under the assumption of fetch limited wave growth condition, various empirical functions of the dynamic roughness can be converted to equivalent expressions for comparison. For datasets covering a wide range of the dimensionless frequency (inverse wave age), it is important to account for the variable rate of wave development at different wave ages. As a result, the dependence of the Charnock parameter on wave age is nonmonotonic. Finally, the analysis presented here suggests that the significant wave steepness is a sensitive property of the ocean surface and a single variable normalization of the dynamic roughness using a wavelength or wave height parameter actually produces more robust functions than bi-variable normalizations using wave height and wave slope.  相似文献   

Seasonal and Spatial Variations of Total Mass Flux around Coral Reefs in the Southern Ryukyus,Japan     

Mohamed?IsmailEmail author  Tadashi?Kimura  Yumiko?Suzuki  Makoto?Tsuchiya 《Journal of Oceanography》2005,61(3):631-644

Total mass flux, size distribution of sediment particles and some chemical components such as total carbon (TC), total nitrogen (TN) and calcium carbonate (CaCO₃) were monitored monthly using a multi-cup sediment traps at seven coral reef sites (6 reef flat and 1 reef slope) of the Marine Protected Areas around Ishigaki, Kohama, Kuroshima and Iriomote Islands in the southern Ryukyus, Japan from September 2000 to September 2001. The size distribution of trapped sediments revealed mostly uni-modal fine sand to mud in the reef flat and gravelly to coarse sand in the reef slope. The total mass flux ranged between 0.54 to 872 gm⁻²d⁻¹, and showed a pronounced seasonality (high in summer-autumn and low in spring) at each site, which was consistent with the rainfall and typhoon regime. Exceptionally high values were observed on the reef slope (Iriomote) in February–March 2001 (1533 gm⁻²d⁻¹) owing to a large amount of bottom sediment re-suspension. On the reef flat (Todoroki South and North; Ishigaki), values obtained in July–August 2001 (872 gm⁻²d⁻¹) and August–September 2001 (800 gm^{− 2}d⁻¹) indicate the high terrestrial discharge from Todoroki River. Trapped sediment particles consist of CaCO₃ (1.2–27.1%) and a non-carbonate fraction (98.8–72.9%), which contains total carbon (4.9–26%), carbonate carbon (CO₂-C) (0.2–3.1%) and non-carbonate carbon (NC-C) (7.9–25.6%). Total nitrogen content was in the range 0.02–0.48%. TN is contained mainly in the carbonate fraction and NC-C may be contained in the non-carbonate fraction. The low TN/OC ratio of the trapped sediments suggests that they were mostly of terrestrial origin and that both fractions migrated. The high total mass flux derived from Todoroki River exceeded the threshold at which a lethal effect on coral community is caused. The results stress the importance of conducting seasonal studies of sedimentation over more than one year and at more than one location in south Japan coral reef ecosystems to gain an understanding of the processes controlling the total mass fluxes and their nutrients content, also to develop an awareness of how to prevent the damage of coral reef ecosystems and, if it does occur, to allow mitigation measures to be undertaken.  相似文献   

Influence of Current Width Variation on the Annual Mean Transport of the East Sakhalin Current: A Simple Model     

Yoichi?ShimadaEmail author  Atsushi?Kubokawa  Kay?I.?Ohshima 《Journal of Oceanography》2005,61(5):913-920

Recent observations suggest that the annual mean southward transport of the East Sakhalin Current (ESC) is significantly larger than the annual mean Sverdrup transport. Motivated by this observational result, transport of a western boundary current has been investigated using a simple numerical model with a western slope. This transport is defined as the instantaneous barotropic transport integrated from the western boundary to the offshore point where the barotropic velocity vanishes. The model, forced by seasonally varying wind stress, exhibits an annual mean of the western boundary current transport that is larger than that of the Sverdrup transport, as observed. The southward transport from October to March in the model nearly equals the instantaneous Sverdrup transport, while the southward transport from April to September decreases slowly. Although the Sverdrup transport in July vanishes, the southward transport in summer nearly maintains the annual mean Sverdrup transport, because the barotropic Rossby wave cannot intrude on the western slope. This summer transport causes the larger annual mean. Although there are some uncertainties in the estimation of the Sverdrup transport in the Sea of Okhotsk, the seasonal variation of the southward transport in the model is qualitatively similar to the observations.  相似文献   

东海区近海强风预报模式     

杨良华 《海洋预报》1995,12(4):34-42

本文探讨东海区近海强风预报模式，首先介绍建立预报模式的思路和步骤，及使用说明，为了验证强风预报模式和判别条件，用１９８６、１９８７上日本传真天气图进行试报，准确和基本准确度为９１．１％，并给出了１９８９、１９９５年随船试验预报结果，准确和基本准确率为９０％以上。  相似文献   

中国对虾弧菌病的药物治疗研究   总被引：1，自引：0，他引：1  

杨季芳  郑国兴 《海洋学研究》1992,10(4):42-50

本文对中国对虾病原弧菌的药物敏感性和最低抑制浓度作了研究,结果表明,氯霉素,四环素,痢特灵和SMZ等药物是治疗成虾轻度弧菌病的有效药物。  相似文献   

安徽宣城地区中晚更新世风成堆积与环境变迁   总被引：25，自引：7，他引：25  

杨达源  房迎三 《海洋地质与第四纪地质》1991,11(2):97-104

通过对宣城向阳中晚更新世沉积剖面的综合研究,认为该剖面与中国北方同时代的黄土—古土壤剖面相比较,虽然长江下游以南地区中晚更新世多个冰期中风成堆积的单层厚度与累积厚度,亦即风成物质的沉积通量与沉积速率均比北方黄土区要小,但它们所反映的气候与环境的变化具有明显的可比性。  相似文献   

台湾海峡西部上升流的生成和长消原因分析     

吴永成  翁学传  杨玉玲 《海洋科学集刊》1997,(38):53-59

台湾海峡西部海域是上升流多发区,近年来已引起众多海洋学家的重视。我国海洋学家通过对台湾海峡区水团、海流和营养盐等的分析研究,不仅得出了台湾海峡西部海域上升流的分布范围和特征,并对其成因也作了探讨,取得了一些有价值的研究结果。由于这些研究都是采用间接方法,因此对上升流的主要成因尚存在不同的看法。本文通过对引起台湾海峡西部海域上升流的各驱动力因子量级的分析,进而判断出上升流的主要成因。  相似文献   

海洋钢筋混凝土结构牺牲阳极保护系统电极行为的研究     

季明棠  倪湘毓  杨芳英 《海洋与湖沼》1995,26(3):275-280

于１９８９－１９９０年在室内条件下，用牺牲阳极保护浸泡于海水中的多种钢筋凝土试件测试不同试件中钢筋极化与阳极布局、涂层质量，涂层厚度及试件浸水情况的关系。结果表明，牺牲阳极能有效地保护全浸海水中的混凝土试件，对间断浸淋海水的试件也有一定的保护作用，通过改善阳极安装工艺，保护作用可望提高；电偶电流在各阴阳极上的分布将随涂层质量，涂层厚度和试件浸水情况不同而异，回路中电阻和电极极化情况是影响电流分布的  相似文献   

天津海岸带经济开发的地质环境和环境工程地质问题   总被引：3，自引：0，他引：3       下载免费PDF全文

杨锦贤 《海洋开发与管理》1994,11(3):36-40

本文揭示了天津海岸带影响经济开发的四个方面的地质环境特点；着重探讨三个方面的环境工程地质问题；并防止其形成和减轻地灾害的对策进行了研究。  相似文献   

中国对虾染色体制备及染色体形态的研究   总被引：6，自引：2，他引：6  

刘萍  麦明  孔杰  王清印  杨丛海 《海洋科学》1994,18(1):33-37

以中国对虾原肠期胚胎为材料，采用整体低渗法和管渗法均制备了染色体。通过比较发现，管渗法制备的染色体比整体低渗法的形态好。本文对制备中国对虾染色体技术方面的问题进行了探讨。通过作者的观察，了解到中国对虾染色体徐正常特征外，还存在较特别的形态特征，如主缢痕增强，次缢痕变化，同源配对等。并对产生这些形态特征的原因进行了解释。  相似文献