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31.
In this paper we review levels of net loss, what happens to the gear once it has been lost, and the resulting levels of ‘ghost catches’ made in passive net fisheries in the EU. We also consider ghost catches resulting from lost gear in other types of fisheries, and the extent to which the value of ghost catches has been quantified. We consider why fishing gear is lost, and profile common management responses. We present a cost benefit model to assess the relative cost effectiveness of different management measures, and suggest that gear retrieval programmes may provide less value for money than other management responses. 相似文献
32.
好望角附近海域春季大风的几种主要形势分析 总被引:1,自引:1,他引:1
通过普查和分析,概括出了春季好望角附近海域三种主要大风出现时的模型图,并以一个月中逐日4次船舶测风报告为例,分析了好望角大风的某些主要特征。 相似文献
33.
Lars Chresten Lund-Hansen Morten Pejrup Jens Valeur Anders Jensen 《Estuarine, Coastal and Shelf Science》1994,38(6)
Gross sedimentation rates (GSR) have been measured using sediment traps placed at nine different levels above the bed (0·3, 0·5, 0·8, 1·0, 2·0, 4·0, 6·0, 8·0 and 10·0 m). The sediment traps were deployed for 1·25 years and recovered 28 times during the study period. Low average GSR values of 5·5 g m-2 day-1 were obtained at 10·0 m, and high average GSR values of 114·8 g m-2 day-1 were obtained at 0·3 m. An expression for the eddy diffusion coefficient of suspended particulate matter (Ks), based on the measured GSR is given. The expression has been used for modelling of Ks at the different trap levels above the bed. High values (≈42 cm2 s-1) of Ks were obtained at the upper traps, whereas low values (≈2 cm2 s-1) were obtained near the bed. Comparison between level of turbulent energy in terms of shear stress at the boundaries of the water column, i.e. from the wind and the bed flow, showed that wind energy exceeded that of the bed flow by a factor 16. At 5·0 m Ks was positively correlated (r=0·66) to the eddy diffusion coefficient of momentum (Km) derived from the wind energy transfer to the water, giving an average β of 0·5 for Ks =βKm. The density difference between surface and bottom waters has been designated a parameter of stratification, and is discussed in relation to variations of Ks and Km . 相似文献
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35.
本文给出了一种从SASS测量的后向散射强度手数据中反演出大尺度海洋风场的新方法。计算结果与Peteherych等利用SASS表面风分析的结果比较在风向上是吻合的,在风速上本文所得结果更宇海面赵实风速。上述结果说明本文所采用的多解排除对两波束散射计探测海面风场的反演是成功的。 相似文献
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Wind and waves are major forces affecting the geomorphology and biota in coastal areas. We present a generally applicable method for measuring and calculating fetch length, fetch direction and wave exposure. Fetch length and direction, measured by geographic information system-based methods, are used along with wind direction and wind speed data to estimate wave height and period by applying forecasting curves. The apparent power of waves approaching the shore, used as a proxy for wave exposure, is then calculated by a linear wave model. We demonstrate our method by calculating fetch lengths and wave exposure indices for five areas with varying exposure levels and types of meteorological conditions in the Finnish Archipelago Sea, situated in the northern Baltic Sea. This method is a rapid and accurate means of estimating exposure, and is especially applicable in areas with geomorphologically varying and complicated shorelines. We expect that our method will be useful in several fields, such as basic biogeographical and biodiversity research, as well as coastal land-use planning and management. 相似文献
38.
一个基于TOPEX卫星极端海面风速预测的海洋地理信息系统 总被引:4,自引:1,他引:4
在基于 TOPEX卫星数据建立全球极端海面风速预测模型的基础上 ,开发出用于极端海面风速预测和可视化预测结果的海洋地理信息系统 (MGIS)。并论述全球极端海面风速预测的意义和 MGIS在预测过程中的重要性及必要性 ;给出全球极端海面风速预测的统计模型 ;简述极端海面风速预测海洋地理信息系统的结构、工作流程和功能 ;同时 ,对系统的预测结果进行初步分析 相似文献
39.
分析1980-1987年欧洲中长期预报中心(ECMWF)每日风场、温度场格点资料及同期南海区域测站和船舶资料,讨论南海低层风场的气候特征。南海为典型的季风活动区,冬季盛行东北季风,夏季盛行西南季风。流场的季节转换表现为季风系统的交替,相应不同的季风系统,南北温度梯度有一逆转过程,南海北部是温度梯度大且发生明显逆转的海区。12°N以南海区气温全年变化极小,整个海区大气温度的季节变化不如流场变化快和显著。 相似文献
40.
本文介绍并叙述了AEL-1型风向、风速仪的设计原理,仪器各部分的电路设计,工作过程及系统软件。该仪器适用于气象台站、工矿企业、海上浮标及科研单位等部门。 相似文献