潮汐强度与咸潮上溯距离试验

采用物理模型实验方法对不同潮差驱动下咸水入侵距离进行实验研究,结果表明存在潮差临界值使得咸水入侵距离最短,当潮差小于该临界值,咸水入侵距离随潮差增大呈快速减小趋势,而大于该临界值则呈缓慢增大趋势。基于实验数据对盐淡水混合进行理论分析,揭示了实验现象的产生机制:①潮差增大过程中盐淡水混合由高度分层变为均匀混合,导致驱动咸潮入侵的动力发生了改变;②当盐淡水为弱混合类型,盐淡水高度分层,重力环流输运是盐进入河口的主要方式,潮汐强度增大减小了盐淡水分层,减弱了重力环流的输运作用,因此入侵距离变小;③当盐淡水为强混合类型,盐淡水混合均匀,重力环流输运作用大大减弱,潮汐扩散成为主要的输运方式,潮汐增强使得扩散能力增大,因此潮汐强度越大,咸潮入侵距离越大。

潮汐强度对河口盐水入侵影响的数值模型研究

为进一步探讨径流和潮汐两大重要动力因子对盐水入侵距离的影响机制,着重分析潮汐强度改变对盐水入侵发展的影响规律和主导过程,该文参考珠江磨刀门河道建立概化河道模型,设置不同驱动条件进行了一系列稳态数值试验。研究结果显示,径流和潮汐对盐水入侵的影响是一个共同作用的动态过程,潮汐增强对盐水运动最直接的影响在于促进盐分垂向输运,而径流对盐水的抬升和上溯起一定抑制作用,潮汐和径流的共同作用影响盐水纵向密度梯度,进而影响盐水入侵过程。因此,在不同流量范围,伴随着潮汐强度的改变,盐水入侵呈现出不同的表现规律。试验条件下,当径流小于3800m3/s且潮差小于2.0m时,盐水入侵距离基本随潮差增加而呈减小趋势。

长江下游近口段近岸鱼类群落多样性及潮汐强度的影响

为了解长江下游近口段近岸鱼类群落多样性及其潮汐的影响,于2016-2017年在靖江样点、2017-2018年在常熟样点分别进行连续4个季度的鱼类调查,同步收集潮汐强度数据。结果表明:靖江样点共监测到鱼类61种,隶属于9目18科47属,鲢(Hypophthalmichthys molitrix)、刀鲚(Coilia nasus)、贝氏?(Hemiculter bleekeri)、草鱼(Ctenopharyngodon idellus)、鳙(Aristichthys nobilis)为主要优势种;常熟样点共监测到鱼类41种,隶属于8目14科34属,鲢、中国花鲈(Lateolabrax maculatus)、鳙、鳊(Parabramis pekinensis)和鲫(Carassius auratus)为主要优势种;靖江样点Margalef指数、Shannon指数和Simpson指数均大于常熟样点,Pielou指数则小于常熟样点;SIMPER分析表明,靖江和常熟样点周年群落组成平均相似度分别为64.5%和64.7%,样点间平均相异度为61.1%;不同季节各潮汐周期内鱼类群落多样性相关分析结果显示,在95%置信区间内,靖江样点物种数、渔获重量、Shannon指数与采样日最大潮差呈极显著正相关(P <0.01),Margalef指数、Simpson指数与最大潮差呈显著正相关(P<0.05),渔获尾数与最大潮差相关不显著;常熟样点物种数与最大潮差呈显著正相关(P<0.05),其余指标与最大潮差相关不显著。本研究为长江下游近口段近岸鱼类群落多样性研究提供了基础资料,为该江段鱼类资源保护与可持续利用提供支撑。

Study on Hydrography and Small-Scale Process over Zhoushan Sea Area

This paper mainly analyzes the tidal characteristics and small-scale mixing process near Zhoushan Islands. First, the spectral analysis and wavelet analysis are adopted for the measured tide level data and tidal current data from the Zhoushan sea area, which indicate that the main tidal cycle near Hulu Island and Taohua Island is semi-diurnal cycle, the diurnal cycle is subordinate. Both their intensities are changed periodically, meanwhile, the diurnal tide becomes stronger when semi-diurnal tide becomes weak. The intensity of baroclinie tidal current weakens at first and then strengthens from top to bottom. Then, in this paper, the Gregg-Henyey （G-H） parameterization method is adopted to calculate the turbulent kinetic energy dissipation rate based on the measured temperature and tidal current data. The results of which shown that the turbulent kinetic energy dissipation rate around Hulu Island is higher than that around Taohua Island. In most cases, the turbulent kinetic energy dissipation rate during spring tide is larger than that during the neap tide; the turbulent kinetic energy dissipation rate in the surface layer and the bottom layer are higher than that in the intermediate water; the changes of turbulent kinetic energy dissipation rate and tidal current are basically synchronous The modeled turbulent kinetic energy dissipation rate gets smaller with the increase of the stratification, however, gets larger with the increase of shearing.