Full-range equation for wave boundary layer thickness

Full-range equation covering all the flow regimes in a wave boundary layer is proposed for the boundary layer thickness. The results are compared with the available experimental data and good agreement has been found. In case of wave boundary layers, there are three definitions of boundary layer thickness in use. Therefore, the full-range equation is derived for three of the definitions. The findings of this study may be useful in calculating suspended sediment transport in coastal environments and studying wave–current combined motion.     

0516号热带风暴过程分析

利用气象海洋数据资料和卫星遥感图片,分析研究了2005年第16号热带气旋"韦森特"(VICENTE)的特征,从最先的初始扰动到自身环流的分裂发展重组过程,以至当时周围相对应的大气环流,发现该热带气旋活动过程具有很多特性。对其移动过程进行的综合分析表明,只要存在合适距离等一定有利的条件,弱的两个涡旋之间完全可以发生强的作用力,高空辐散场的抽气作用对气旋的发展有极好的作用,所得的结论可对今后的预报提供一些启示和参考。     

珠江口伶仃洋锋的类别及其对沉积的影响

根据近年在珠江口伶仃洋的观测资料，对比国外有关河口锋的定义，归纳了伶仃洋内几种锋的现象，计有潮侵锋、岬角锋及湖水退急时的浅滩锋等。解释了锋生的原因与潮汐进退，特别与随潮入侵的咸水关系。文中也探讨了这些锋对沉积环境的影响，认为它是陆架水入侵河口地区的一种不容忽视的沉积动力过程。     

Elucidating the dynamics and mixing agents of a shallow fjord through age tracer modelling

The mixing agents and their role in the dynamics of a shallow fjord are elucidated through an Eulerian implementation of artificial tracers in a three-dimensional hydrodynamic model. The time scales of vertical mixing in this shallow estuary are short, and the artificial tracers are utilized in order to reveal information not detectable in the temperature or salinity fields. The fjord's response to external forcing is investigated through a series of model experiments in which we quantify vertical mixing, transport time scales of fresh water runoff and estuarine circulation in relation to external forcing.Using age tracers released at surface and bottom, we quantify the time scales of downward mixing of surface water and upward mixing of bottom water. Wind is shown to be the major agent for vertical mixing at nearly all depth levels in the fjord, whereas the tide or external sea level forcing is a minor agent and only occasionally more important just close to the bottom. The time scale of vertical mixing of surface water to the bottom or ventilation time scale of bottom water is estimated to be in the range 0.7 h to 9.0 days, with an average age of 2.7 days for the year 2004.The fjord receives fresh water from two streams entering the innermost part of the fjord, and the distribution and age of this water are studied using both ageing and conservative tracers. The salinity variations outside this fjord are large, and in contrast to the salinity, the artificial tracers provide a straight forward analysis of river water content. The ageing tracer is used to estimate transport time scales of river water (i.e. the time elapsed since the water left the river mouth). In May 2004, the typical age of river water leaving the fjord mouth is 5 days. As the major vertical mixing agent is wind, it controls the estuarine circulation and export of river water. When the wind stress is set to zero, the vertical mixing is reduced and the vertical salinity stratification is increased, and the river water can be effectively exported out of the fjord.We also analyse the river tracer fields and salinity field in relation to along estuary winds in order to detect signs of wind-induced straining of the along estuary density gradient. We find that events of down estuary winds are primarily associated with a reduced along estuary salinity gradient due to increased surface salinity in the innermost part of the fjord, and with an overall decrease in vertical stratification and river water content at the surface. Thus, our results show no apparent signs of wind-induced straining in this shallow fjord but instead they indicate increased levels of vertical mixing or upwelling during down estuary wind events.     

分潮波模型多资料数值计算方法研究 Ⅰ.岸边资料运动学外推的第一边值方法

对于含多资料三维分潮波模型建立了一种岸边资料运动学外推的潮波第一边值方法，并对渤海的四大原湖波进行试算。结果证实本方法可行，该方法使潮波方程既满足第一边值问题，充分利用岸边测站资料，又保证岸界法向流速为零条件，符合物理意义。并对复型病态矩阵的收敛问题提出了一种可行性处理。     

0220号热带风暴(米克拉)特征分析

南海是热带气旋活动较为频繁的地区之一。该地区因其独特的地理环境和复杂的热带大气环流系统，在热带气旋预报工作上存在一定的困难。本文在分析一些气象图表资料的基础上，对2002年第20号热带风暴(米克拉)的形成、发展及消亡进行了探讨和研究。主要从形成的背景环流，气旋的结构等方面入手，总结出一些该气旋所具备韵特有流场，从而为以后的南海自生热带气旋预报工作积累一定经验。     

减少航道外波浪集聚对策研究

进港航道开挖引起波能重新分布 ,导致航道外近区域波能聚集 ,波高增大 ,从而影响防波堤稳定及港内泊稳条件。文章介绍了 Boussinesq方程的推导过程和发展过程 ,基于深水和缓变地形的色散关系 ,建立了波浪数学模型。该模型可用于研究深水和浅水地区波浪的浅水变形、折射、绕射和反射。并提出了减少波能聚集、降低堤前波高的多种措施。结合大窑湾港实际工程 ,经过多方面的数物模比选 ,利用数学模型优化出一种可行的喇叭口航道开挖方案并付诸实施 ,降低了防波堤的堤前波高 ,满足了预期的设计要求。     

龙口的海风及其影响

本文运用龙口气象站近５年自记风资料及实测探空资料，分析了龙口海风的生消规律、海风强度、空间结构及海风生成后对温、湿度的影响。同时为分析海风环流对大气污染物的影响。本文提出了一个简单地计算热内边界层的方法。     

Longshore drift estimation using fluorescent tracers: New insights from an experiment at Comporta Beach, Portugal

A fluorescent sand-tracer experiment was performed at Comporta Beach (Portugal) with the aim of acquiring longshore sediment transport data on a reflective beach, the optimization of field and laboratory tracer procedures and the improvement of the conceptual model used to support tracer data interpretation.

The field experiment was performed on a mesotidal reflective beach face in low energetic conditions (significant wave height between 0.4 and 0.5 m). Two different colour tracers (orange and blue) were injected at low tide and sampled in the two subsequent low tides using a high resolution 3D grid extending 450 m alongshore and 30 m cross-shore. Marked sand was detected using an automatic digital image processing system developed in the scope of the present experiment.

Results for the two colour tracers show a remarkable coherence, with high recovery rates attesting data validity. Sand tracer displayed a high advection velocity, but with distinct vertical distribution patterns in the two tides: in the first tide there was a clear decrease in tracer advection velocity with depth while in the second tide, the tracer exhibited an almost uniform vertical velocity distribution. This differing behaviour suggests that, in the first tide, the tracer had not reached equilibrium within the transport system, pointing to a considerable time lag between injection and complete mixing. This issue has important implications for the interpretation of tracer data, indicating that short term tracer experiments tend to overestimate transport rates. In this work, therefore, longshore estimates were based on tracer results obtained during the second tide.

The estimated total longshore transport rate at Comporta Beach was 2 × 10^− 3 m³/s, more than four times larger than predicted using standard empirical longshore formulas. This discrepancy, which results from the unusually large active moving layer observed during the experiment, confirms the idea that most common longshore transport equations under-estimate total sediment transport in plunging/surging waves.