海浪破碎对海洋上混合层中湍能量收支的影响

海浪破碎产生一向下输入的湍动能通量,在近海表处形成一湍流生成明显增加的次层,加强了海洋上混合层中的湍流垂向混合。为了研究海浪破碎对混合层中湍能量收支的影响,文中分析了海浪破碎对海洋上混合层中湍流生成的影响机制,采用垂向一维湍封闭混合模式,通过改变湍动能方程的上边界条件,引入了海浪破碎产生的湍动能通量,并分别对不同风速下海浪破碎的影响进行了数值研究,分析了混合层中湍能量收支的变化。当考虑海浪破碎影响时,近海表次层中的垂直扩散项和耗散项都有显著的增加,该次层中被耗散的湍动能占整个混合层中耗散的总的湍能量的92.0%,比无海浪破碎影响的结果增加了近1倍;由于平均流场切变减小,混合层中的湍流剪切生成减小了3.5%,形成一种存在于湍动能的耗散和垂直扩散之间的局部平衡关系。在该次层以下,局部平衡关系与壁层定律的结论一致,即湍动能的剪切生成与耗散相平衡。研究结果表明,海浪破碎在海表产生的湍动能通量影响了海洋上混合层中的各项湍能量收支间的局部平衡关系。     

波生运动和波湍相互作用对海洋上混合层影响的数值探究

本文将波生运动和波湍相互作作用的参数化方案嵌入一维垂向混合模式GOTM中,并与不考虑波浪效应以及仅考虑波浪破碎的试验结果进行对比,发现不考虑波浪效应时,海表温度模拟结果偏高,混合层深度模拟结果偏浅,偏差在夏季尤其明显。波浪破碎对湍流的增强作用仅限于上层几米甚至仅限于表层,对整个混合层的温度分布和混合层深度影响不大。波生运动和波湍相互作用则有效增强海洋上层的湍流强度,改善模式高估海表温度而低估混合层深度的问题,温度分布模拟结果降低了上层温度同时增大了次表层温度,与观测更加相符。波生运动和波湍相互作用增大了海洋上层的湍流剪切生成项、湍动能、耗散率和湍流输运系数,两者对上混合层的温度分布、湍流强度和湍流输运作用的改善结果十分相似。波生运动和波湍相互作用的影响在冬季并不明显,此时可能有其他混合机制占主导地位。     

夏季长江口及其邻近海域湍流特征分析

利用2019年7月在长江口科学考察实验研究夏季航段(NORC2019-03-02)中获得的MSS90L湍流剖面仪的直接观测数据,本文计算并分析了该断面的湍动能耗散率ε和垂向湍扩散系数K_Z的分布情况。湍动能耗散率的大小为1.72×10?10～2.95×10?5 W/kg;垂向湍扩散系数的大小为3.24×10?7～4.55×10?2 m2/s。湍动能耗散率和垂向湍扩散系数的分布相似,均为上层最强,底层次之,中层最弱。上层由于风应力的作用,使得湍动能耗散率和垂向湍扩散系数较大;温跃层处层化较强,抑制了湍动能的耗散和垂向上的湍混合。盐度锋面的次级环流会促使低盐水团脱离,锋面引起的垂向环流会加强海洋的湍混合。低盐水团与外界的能量交换较少,湍动能耗散率较弱。长江口海区存在明显的上升流和下降流,它们是由锋面的次级环流产生的;上升流和下降流的存在促进湍动能的耗散与湍混合。     

基于舟山外海连续测站的湍混合研究

利用2010年4月3日在舟山外海观测的25hLADCP海流数据与CTD连续观测数据,综合利用Thorpe方法、功率谱分析、交叉谱分析等方法对测站所在海域的小尺度湍混合参数进行估计,分析并讨论了其时空分布特征及影响因子。研究结果表明,上混合层湍流所致的垂向翻转尺度普遍大于下混合层,较大尺度翻转均出现在潮位峰值附近,涨潮时段混合明显大于落潮时段且半日周期,1/4周期显著。该站点存在明显的"上强下弱"双密度跃层现象,湍动能耗散率、湍混合率也呈现出"表强底弱"特征。弱跃层中近惯性频率的内波和近半日潮频率的内潮信号最为显著,而强跃层中则是高频内波和近半日潮频率的内潮信号明显,上下跃层及其之间伴有间歇性强湍流发生。上混合层平均的湍混合对风应力的响应要快于对海流的响应,底应力是下混合层水体湍混合的重要因子。     

垂向混合参数化方案对模拟黄海夏季上层温度结构的影响研究

采用POMgcs(Princeton Ocean Model with generalized coordinate system)和MITgcm(MIT General Circulation Model)两个海洋数值模式,研究了M-Y2.0、基于固壁近似假定的M-Y2.5、基于波浪破碎作用的M-Y2.5和KPP 4种垂向混合参数化方案对模拟黄海夏季上层温度结构的影响。结果表明,M-Y2.0和基于固壁近似假定的M-Y2.5方案低估了黄海上层的湍动能,模拟的黄海夏季温度上混合层的效果与实测相比均偏浅,不能够很好地重构黄海夏季温度的垂直结构。而基于波浪破碎作用的M-Y2.5和KPP方案均可以增加海洋上层湍动能的输入量,模拟的黄海夏季温度上混合层的效果与实测较为一致。故推测黄海夏季的上层结构是受波浪混合和流场剪切等物理机制共同调节的,若通过合理的垂向混合参数化方案将这些物理机制的作用加以体现,将会较真实地模拟和重构出黄海夏季海温上层结构。     

渤海弱层化期湍流混合观测特征分析

利用2017年9月在渤海共享航次中取得的湍流混合直接观测数据,本文研究了渤海海域湍流混合的空间分布特征及有关的影响因素。9月观测海区水体垂向层结较弱,莱州湾受黄河冲淡水影响出现高温低盐结构,位于渤海中央浅滩南北两侧洼地的双中心冷水结构依旧存在。湍流观测结果表明湍动能耗散率在10~(-9)～10~(-5)W/kg之间变化,统计上满足对数正态分布。耗散率强值区出现在辽东湾及渤海湾湾口近岸处,相应的垂向湍扩散系数约为10~(-6)～10~(-2)m~2/s。垂向上,水体表、底层混合较强,进一步研究发现弱层化水体的平均湍动能耗散率〈ε〉与风速和正压潮流速的大小存在正相关关系。另一方面,耗散率ε与浮性频率N近似满足ε=2.0×10~(-8)+3.0×10~(-7)(N~2/N_0~2)~(-5)的拟合函数关系,反映了层化对水体垂向混合的抑制作用。     

北黄海海域大气湍流强度特征及风速标准差相似性分析

根据国家海洋局"908"专项北黄海海区海洋气象观测资料,计算了2007～2008年间该海区4个不同季节的大气湍流强度并与其他海区及陆地下垫面大气湍流值相比较.北黄海海区大气湍流强度量级为10-2,比陆地下垫面大气湍流强度低一个量级.由于海洋的特殊性质,对秋季大气湍流强度日变化的分析发现,在大气湍流强度的影响因素中,海洋的热力作用相对较大.对水平方向风速标准差是否满足Monin-Obukhov相似关系进行了探讨,数据显示,在不稳定层结下冬季水平方向无量纲风速标准差与Z/L的关系,基本满足1/3次方律.秋冬在不稳定层结下垂直方向风速标准差满足Monin-Obukhov相似理论.     

热力学效应及斯托克斯漂流对混合层影响的研究

本文通过理想化的外部强迫以及海洋站点实测数据驱动普林斯顿海洋模式来研究海洋热力学效应和斯托克斯漂流对上混合层数值模拟的影响。在Mellor-Yamada湍流闭合方案中,经常出现夏季海表面温度偏暖和混合层深度偏浅的模拟误差。实验表明,斯托克斯漂流在冬季和夏季均能增强湍流动能,加深混合层深度。这种效应可以改善夏季的模拟结果,但与观测数据相比,将增大冬季混合层深度的模拟误差。斯托克斯漂流可以通过增强湍动能来加深混合层深度。结果表明,将斯托克斯漂流与冷皮层和暖层对上部混合层的热效应相结合,可以正确地模拟混合层深度。在夏季,海洋冷皮层和暖层通过“阻挡结构”和双温跃层结构模拟出更真实的上混合层变化。在冬季,海洋热力学效应通过增强上层海洋层结平衡了斯托克斯漂流的影响,并且由斯托克斯漂流引起的过度混合被校正。     

春季南海南部上混合层数值模拟与数值实验

采用一维湍动能模式对南海南部的 SST及混合层进行数值模拟和数值试验。结果表明 :TKE模式能够模拟南海南部的海表面温度 SST以及除南海南部 5月中旬以外的上混合层深度随时间变化基本特征。在 5～ 6月 ,SST的日振荡主要依赖于短波辐射的日变化 ,风的混合作用抑制了 SST的日周期振荡。春季夏季风爆发期间 ,南海海面潜热通量和感热通量与短波辐射和风应力相比较 ,是一个对 SST和混合层影响较小的量。在春季南海南部 ,短波辐射作用能使 SST升高的最大值约为 4℃ ;潜热和感热通量能使 SST的下降的最大值为 3℃。风应力对南海混合层深度随时间变化趋势起着决定的作用 ,并能使其深度加深 2 0～ 30 m,而短波辐射则使混合层的深度变浅2～ 3m,潜热和感热通量会使混合层的深度加深 1～ 2 m。在春季南海南部 ,热通量对混合层深度的影响与风应力相比要小得多     

春季南海北部上混合层的数值模拟与数值实验

根据 1 998年南海季风实验 (SCSMEX)北部“实验 3号”调查船的观测资料 ,采用一维湍动能模式 (TKE模式 ) ,对春季南海北部的SST及混合层随时间变化特征进行了数值模拟和数值试验。结果表明 ,TKE模式能够很好地模拟南海北部的海表面温度SST和上混合层深度随时间变化基本特征。在南海 5— 6月 ,SST的日振荡主要依赖于短波辐射的日变化 ,短波辐射是SST的主要维持机制 ;短波辐射会使SST升高 1— 4℃ ;风的垂直混合作用主要是抑制了SST的日周期振荡。春季南海海面潜热通量和感热通量与短波辐射和风应力相比较 ,是一个对SST影响较小的量。南海北部 5月份混合层深度的变化趋势和振荡特征受风应力和短波辐射共同控制 ,风应力使混合层深度加深 5— 1 0m ,短波辐射使混合层深度平均变浅 5— 1 0m。而 6月份南海北部 ,在夏季风爆发后短波辐射较小 ,短波辐射的作用只能使混合层深度变浅1— 2m ,潜热通量和感热通量对混合层的作用会使混合层的深度加深 1— 2m ,混合层深度主要受风应力控制。     

海上大直径钢管桩打桩过程中桩周土强度弱化研究

海上大直径钢管桩打桩过程中,桩周土体受到强烈扰动而发生强度弱化,掌握桩周土体强度弱化规律对于准确预测打桩过程、保证工程安全具有重要意义。为研究土体强度弱化规律,开展了环剪试验模拟打桩对桩周土体的扰动,测试土体强度随剪切速率的变化规律,建立了描述土体强度弱化规律的拟合公式,引入到打桩分析软件中。研究结果表明：土体的强度折减程度不仅与土体本身的性质有关还受到土体的埋深和剪切速率的影响,埋深越深土体强度折减程度越低,剪切速率越高土体强度折减越高,在打桩分析中可采用这里推荐的线性折减方法来模拟不同深度处土体强度的折减规律。     

Phylogenetic diversity and phenotypic characterization of cultivable bacterioplankton isolated from polar oceans

A set of 27 marine planktonic bacteria isolated from the polar regions was characterized by 16S rDNA sequencing and physiological and biochemical testing. More than half of these bacteria were positive for caseinase, gelatinase and 13-glucosidase, and could utilize glucose, maltose or malic acid as carbon source for cell growth. Twelve isolates expressed nitrate reduction activities. Except for one antarctic isolate BSwlO175 belonging to Actinobacteria phylum, these isolates were classified as γ-Proteobacteria, suggesting that γ-Proteobacteria dominated in cultivable marine bacterioplankton at both poles. Genus Pseudoalteromonas was the predominant group in the Chukchi Sea and the Bering Sea, and genus ShewaneUa dominated in cultivable bacterioplankton in the Prydz Bay. With sequence similarities above 97%, genus Psychrobacter was found at both poles. These 27 isolates were psychrotolerant, and significant 16S rDNA sequence similarities were found not only between arctic and antarctic marine bacteria （ 〉 99% ）, but also between polar marine bacteria and bacteria from other aquatic environments （ ≥ 98.8% ）, including temperate ocean, deep sea, pond and lake, suggesting that in the polar oceans less temperature-sensitive bacteria may be cosmopolitan and have a bipolar, even global, distribution at the species level.     

Estimation of Sediment Properties during Benthic Impact Experiments

Sediment properties, such as water content and density, have been used to estimate the dry and wet weights, as well as the volume of sediment recovered and discharged, during benthic impact experiments conducted in the Pacific and Indian Oceans. The estimates show that the weights of dry (355-1332 t) and wet sediment (1651-4888 t) recovered during the experiments, are not only a function of the total duration and distance covered during the experiment, but also depend on water content and density of the sediment. Estimation of dry sediment and its volumetric ratio in the discharge, are key parameters for calculating the discharged volume. The estimated volume of wet sediment recovered (1427-4049 m 3 ) as well as discharged (2693-6951 m 3 ) during the experiments, provide important inputs to evaluate the sediment resettlement and migration. Using these estimates, the average depth of excavation on the seafloor, can also been calculated. However, the stages of sediment recovery and discharge are expressed differently in some of the experiments. In order to standardize these, different stages have been identified, and definitions of certain terms have been suggested, for use in the future. The methods of calculating different properties, as well as weight and volume of discharged sediment are described in the paper for use in other applications concerning deep-sea discharges.     

A Tidal Flow Model for the Gulf of Kachchh, India

A vertically integrated model has been used to study the tidal circulation and currents in the Gulf of Kachchh along the west coast of India. The model is fully nonlinear and uses a semiexplicit finite difference scheme to solve the basic hydrodynamic equations on a staggered grid. The model is forced by prescribing the tides along the open boundary of the model domain. The flow is simulated both with and without the presence of the proposed tidal barrage across the Hansthal Creek in the Gulf of Kachchh. The results show a considerable change in the behavior of the tidal flow in the presence of the barrage.     

利用中国GF-3卫星SAR和HY-2A卫星微波散射计的首次台风联合定量观测

<正>The typhoon,as a mature tropical cyclone that develops in the western part of the North Pacific Ocean with high wind speed and heavy rainfall,is one of the most lethal and costly of natural disasters for the densely populated countries of East Asia.It can be easily detected by space-borne sensors operated at microwave,visible or infrared bands(Liu et al.,2014).Synthetic Aperture Radar(SAR)is     

离子交换—原子吸收光谱法测定海水中痕量铜、铅、锌、镉、铁、锰

本文介绍了用国产D401型螯合树脂分离富集海水中铜、铅、锌、镉、铁、锰等痕量元素,并用原子吸收光谱仪测定其含量的方法。讨论了各元素的分离条件选择及干扰元素的影响,并与溶剂萃取法的结果作了比较。各元素检测的定量下限为:铜0.5μg/L、铅0.1μg/L、锌1.0μg/L、镉0.01μg/L、铁2.0μg/L、锰2.0μg/L。方法精密度在4—8％之间,回收率为90—102％。     

Biogeochemistry of Mangrove Soil Organic Matter: a Comparison BetweenRhizophoraandAvicenniaSoils in South-eastern Brazil

Soil core samples fromRhizophora mangleL. andAvicennia schauerianaStapf & Leech forests from south-eastern Brazil were analysed for their total organic matter content and their sugars, amino acid and amino sugars composition. Organic carbon and nitrogen contents were higher inAvicenniathan inRhizophorasoils. The contribution of sugars and amino acids to the total organic carbon pool was constant with depth inRhizophorasoils whereas inAvicenniasoils it increased. Spectral distribution of sugars and amino acids showed a dominance of Ca-affine monomers, particularly acidic amino acids, and the sugar arabinose. Biogeochemical indicators derived from ratios of individual sugar and amino acid monomers confirm previous studies which showed that organic matter in both soils is mainly of mangrove origin. The results further suggest accumulation of organic matter inRhizophorasoils and a continuing degradation of organic matter inAvicenniasoils. The latter may thus release more nutrients to adjacent ecosystems thanRhizophorasoils.     

A review of orange roughy Hoplostethus atlanticus fisheries,estimation methods,biology and stock structure

Orange roughy Hoplostethus atlanticus are unusual fish. They form dense aggregations that have fuelled lucrative fisheries at great depths (600–1 400 m), especially off Namibia, New Zealand and Australia. They are thought to be very long-lived (>100 years, maturity at 22 – 40 years), and to have exceptionally low natural mortality (M = 0.045–0.064 year^?1) and slow growth rates (K = 0.055–0.070 year^?1). In addition, they spawn large eggs and have low fecundity. These factors combine to make orange roughy highly susceptible to overfishing; most stocks are below 30% of pristine levels. Assessments are obtained from indices of catch rate and trawl, acoustic and egg surveys. Acoustic estimates are the most direct, but are confounded by the species' low target strength (?50 to ?53 dB)–attributable to the wax-filled swim bladder. Extracellular wax esters are stored in abundance and comprise mostly mono-unsaturated fatty acids, with low concentrations of the ω-3 fatty acid family. This unusual composition (resultant from the species' diet) ensures neutral buoyancy. Stock separation has been inferred mainly from biological studies, but genetic studies have also found differences among stocks within New Zealand and Australia. Deep-water habitat may be damaged by trawling operations and may take many years to recover, so in some quarters there is a call for a portion of suitable habitat to be set aside for preservation. Although Namibian orange roughy are shallower, smaller and younger than those in other stocks, the Namibian fishery sustained high catches for only a few years before quotas were reduced, from 12 000 to 1 875 tons. Three management lessons are suggested for developing orange roughy fisheries based on the Namibian experience: (1) imposition of catch limits during exploratory fishing; (2) starting the acoustic surveys earlier in the fishery, if possible; (3) greater reliance on trends in catch rate until a survey series has been established.