深海环境中溢油输移扩散的初步数值模拟

通过对溢油在深海环境中的输移过程及行为特点的分析,初步建立基于拉格朗日积分法的深海溢油模型.该模型除了能够模拟油气混合物在真实深海环境中的共同输移与分离输移扩散过程,还考虑了石油溶解、气体溶解、天然气水合物形成与分解等行为变化对溢油运动轨迹的影响.应用该模型初步数值模拟了一次实际深海溢油试验,结果表明溢油在水下的空间分...     

中国近海蒸发波导的数值模拟与预报研究

利用中尺度大气模式MM5对2007年中国近海大气蒸发波导进行了全年的高分辨的数值模拟。模拟结果统计表明,整个海域蒸发波导的平均出现概率约为90%。本文重点关注强度较大的蒸发波导,详细分析了其季节分布特征及其与海洋环流和海面气象条件的相关关系。研究发现,25°N以南的开阔海域的蒸发波导出现概率全年都较高,而以北的东海西北部、黄海与渤海,蒸发波导的出现概率呈现明显的季节特征;蒸发波导的空间分布受中国近海海洋环流的强烈影响,存在1个与黑潮区域相一致的带状波导高出现概率区域,台湾暖流、黄海暖流和对马暖流使得在某些季节相应海域蒸发波导出现概率高于其周围海域。此外,本文还基于WRF模式及其3DVAR系统构建了大气波导数值预报系统,尝试对中国东南海域的蒸发波导进行数值预报。     

辐射应力对台风风暴潮预报的影响和数值研究

台风过程期间,风暴潮和海浪是相伴相生的,相互作用的.波致辐射应力对于近岸风暴增、减水起着十分重要的作用,传统的海浪模式计算辐射应力耗时较多,不能满足业务化预报的要求.根据已有波浪辐射应力的理论表达式,经过严密的数学推导,适当的简化处理,提出了一个较为简单的波浪辐射应力表达式,并将其应用到业务化风暴潮数值预报模式中去,通...     

Modified PIC Method for Sea Ice Dynamics

The sea ice cover displays various dynamical characteristics such as breakup, rafting, and ridging under external forces. To model the ice dynamic process accurately, the effective numerical modeling method should be established. In this paper, a modified particle-in-cell （PIC） method for sea ice dynamics is developed coupling the finite difference （FD） method and smoothed particle hydrodynamics （SPH）. In this method, the ice cover is first discretized into a series of lagrangian ice particles which have their own sizes, thicknesses, concentrations and velocities. The ice thickness and concentration at Eulerian grid positions are obtained by interpolation with the Gaussian function from their surrounding ice particles. The momentum of ice cover is solved with FD approach to obtain the Eulerian cell velocity, which is used to estimate the ice particle velocity with the Gaussian function also. The thickness and concentration of ice particles are adjnsted with particle mass density and smooth length, which are adjusted with the redistribution of ice particles. With the above modified PIC method, numerical simulations for ice motion in an idealized rectangular basin and the ice dynamics in the Bohai Sea are carried out. These simulations show that this modified PIC method is applicable to sea ice dynamics simulation.     

A three-dimensional model study on ocean dynamic response to traveling cyclone over the Huanghai Sea

On the basis of numerical simulation of the mean circulation and relevant thermal-salinity fields in June with a three-dimensional ocean model (ECOM-si), the model outputs are used as first guess of initial fields for numerical integration of the model equations and the numerical results are applied to investigating the dynamical responses of the Huanghai Sea and the East China Sea (HECS) in the course of a weak land-to-sea cyclone‘s passage over the Huanghai Sea on 15-16 June 1999. Predominance of the dynamic impact of cyclone over the thermal one in June in the HECS is justified using observations and model simulations.The cyclone and its surrounding weather system, i.e,, subtropical high ridge to its south could influence current and thermal fields in the Bohai Sea, the Huanghai Sea and the northern East China Sea even though the intensity of cyclone was rather weak. The response of oceanic currents to the wind stresses driven by the cyclone and its southern subtropical high were strongly characterized by the wind drift with its extent of equivalent scale of cyclone in the horizontal and of Ekman layer in the vertical. The sea response at a given site was closely related to the transient local wind speed and direction,especially was sensitive to the local wind direction,which is demonstrated at three points locating at the southern and western Huanghai Sea and the northern East China Sea. So the sea responses at locations differed considerably from one another. Current responded to the wind stress in a simple way:directly to the wind-driven current and subsequent gradient current and slope current, etc., whereas sea temperature responded to the wind stress in two ways: directly to the cyclone-induced cooling and indirectly to water movements both in the horizontal and the vertical by the cyclone‘ s wind stress. So the sea temperature variation under the influence of cyclone was more complicate than the current. The HECS in response to the cyclone and its ambient weather system was likely to be a fast process and such a response could last at least for more than 1d. Current increased with the duration of wind stress exerted on the surface and decreased with the increasing depth. Affected by the cyclone, the maximum sea surface temperature decreased by almost 1.6℃ during the 24h cyclone.     

双涡互旋的数值模拟试验

本文应用准地转正压无辐散模式对双涡的相互作用进行了数值模拟试验。试验结果表明：（1）只考虑相对涡度平流的情况下双涡以互旋为主，而且随着初始间距的缩小，互旋越来越明显。双涡的相互作用与它们的初始间距以及它们的强度和结构有密切的关系。（2）双涡的移动加速和减速都是出现在它们移动方向改变的时刻，当移动方向向逆时针方向变化时移速减慢，否则加快。     

西沙湾工程波浪推算及波浪场数值模拟

本研究根据崇武水文站1976—2007年共31 a的波浪观测资料,使用皮尔逊Ⅲ型频率曲线进行拟合分析,推算出崇武在不同重现期条件下的特征波浪要素,再将其作为外海波浪要素输入,通过基于椭圆型缓坡方程的CGWAVE近岸波浪数值模型,模拟西沙湾的重现期波浪场,得到其设计波浪要素,得到较为合理的计算结果。西沙湾的海底地形强烈地影响近岸波浪,导致了波高和波向的不均匀分布特征,岛屿和礁石都是天然屏障,东侧水域受龟屿及闽台码头的掩护,波浪反射、绕射明显,对避风坞起到了有效的保护作用。此外,对于不同地质的边界,反射系数不同使得近岸波高分布有较大差异。     

Macrobenthic Communities of the Eastern Mediterranean Continental Shelf

Abstract. The results of a year long study in which soft-bottom epibenthic invertebrates were collected by grab, dredge and beam-trawl, along the southern Mediterranean coast of Israel, are described in this paper. The classificatory analysis used for both normal and inverse analyses used two measures of dissimilarity - Canberra metric and Bray-Curtis, and both group-average and nearest-neighbour clustering. The results were displayed as dendrograms. Four site groups and five species groups characterised a total of 58 site samples and 245 species. The prominent species in each of the five species groups are mentioned. The applicability of "community concepts" and the effects of sediment properties on community structure are discussed.     

Parabolic Wave Propagation Modelling in Orthogonal Coordinate Systems

This paper presents a numerical model study of the propagation of water waves using the parabolic approximation of the mild-slope equation in the orthogonal coordinate system. Two types of coordinate systems are studied: (a) a general form of orthogonal coordinate system and (b) the conformal system, a special form of orthogonal coordinate system. Two typical examples, namely, expanded breakwaters and a circular channel, are studied to validate the model. First, the examples are studied by use of the general orthogonal coordinates. Then the same examples are computed by use of the confonnal system. The computational results show that the confonnal coordinate system generally gives better predictions than the general orthogonal system. A numerical technique for generating the conformal grid is combined with the numerical model to improve the practicability of the model. The comparison between the result from the numerical grid system and that from the analytical grid system shows that reliable computational results can be obtained by use of the numerical confonnal grid system.     

Effect of the Twin Jetties as A Regulating Structure at the Tao-er Estuary

The phase one project of the twin jetties at the Tao-er Estuary yields no effect on the flow, and there is a large area of deposition. A numerical model is employed to simulate the flow field, and the scouring and silting in the channel be-tween the two jetties are analyzed. The results show that the effective tidal flux between the two jetties is reduced due to the notch located at the heel of the east jetty, and the effect of contraction-flush is not obvious. As for the regulation of this kind of estuary under the tide action, the capability of tidal flux should be fully used.