Upper ocean high resolution regional modeling of the Arabian Sea and Bay of Bengal

In this paper, effort is made to demonstrate the quality of high-resolution regional ocean circulation model in realistically simulating the circulation and variability properties of the northern Indian Ocean(10°S–25°N,45°–100°E) covering the Arabian Sea(AS) and Bay of Bengal(BoB). The model run using the open boundary conditions is carried out at 10 km horizontal resolution and highest vertical resolution of 2 m in the upper ocean.The surface and sub-surface structure of hydrographic variables(temperature and salinity) and currents is compared against the observations during 1998–2014(17 years). In particular, the seasonal variability of the sea surface temperature, sea surface salinity, and surface currents over the model domain is studied. The highresolution model's ability in correct estimation of the spatio-temporal mixed layer depth(MLD) variability of the AS and BoB is also shown. The lowest MLD values are observed during spring(March-April-May) and highest during winter(December-January-February) seasons. The maximum MLD in the AS(BoB) during December to February reaches 150 m (67 m). On the other hand, the minimum MLD in these regions during March-April-May becomes as low as 11–12 m. The influence of wind stress, net heat flux and freshwater flux on the seasonal variability of the MLD is discussed. The physical processes controlling the seasonal cycle of sea surface temperature are investigated by carrying out mixed layer heat budget analysis. It is found that air-sea fluxes play a dominant role in the seasonal evolution of sea surface temperature of the northern Indian Ocean and the contribution of horizontal advection, vertical entrainment and diffusion processes is small. The upper ocean zonal and meridional volume transport across different sections in the AS and BoB is also computed. The seasonal variability of the transports is studied in the context of monsoonal currents.     

杭州湾及其邻近海域表层沉积物的沉积环境分区及重金属污染特征分析

于2017年春季和2018年春季,分两个航次,在杭州湾及其邻近海域采集了表层沉积物样品,并对其粒度组成及重金属含量进行了测定。结果表明,研究区域表层沉积物的粒级组成以砂和粉砂为主,平均占比分别为38.0%和55.4%。根据粒级组成的区域分布特征,将研究区域分为长江河口现代沉积区(Ⅰ-1)、钱塘江河口现代沉积区(Ⅰ-2)、长江羽状锋面积聚区(Ⅱ-1)、长江次级锋面积聚区(Ⅱ-2)、岛屿风化影响区(Ⅲ)、残留砂混合沉积区(Ⅳ)等4大类6个亚区。通过比较不同区域重金属含量发现,总体分布趋势为Ⅱ-1区和Ⅱ-2区含量较高,Ⅰ-2区和Ⅳ区含量较低,Ⅰ-1区和Ⅳ区相对居中。单因子污染指数评价结果显示,Ⅱ-1区和Ⅱ-2区的Cu、Pb、Zn、As、Cd、Hg已呈现出污染态势,需引起关注;Cr则未呈现出污染态势。     

日本“3·11”海啸引起的乐清湾共振研究

本文基于TELEMAC-2D模型建立太平洋区域海啸传播模型,模拟2011年日本“3·11”海啸事件下海啸波的传播。使用实测数据对该模型进行验证,在模型验证良好的基础上分析日本“3·11”海啸事件对乐清湾的影响。通过频谱分析得到“3·11”海啸激发的乐清湾内240、180和103 min这3个主导模态的幅值及其相位。通过白噪声实验对乐清湾的固有共振特征进行估算,进一步支持了乐清湾在上述3个模态发生共振这一结论。白噪声实验还表明,海啸等海洋灾害发生时会在乐清湾湾顶及湾口处产生较大的增水,该结论对乐清湾内海洋灾害风险防范具有指导意义。     

基于DINEOF的静止海洋水色卫星数据重构方法研究

静止轨道海洋水色成像仪(Geostationary Ocean Color Imager, GOCI)提供了时间分辨率达小时级的海洋水色数据,使得对海洋环境的逐时变化监测成为可能。然而受到海洋上空云、雾和霾的影响,数据出现连续高缺失率甚至完全缺失的情况,使得数据使用价值大大降低。在经验正交函数重构法(Data INterpolating Empirical Orthogonal Functions, DINEOF)的基础上,突出时间要素在重构中的地位,运用异常像元检测、拉普拉斯平滑滤波和时间模态2次分解插值,提出了适用于静止海洋水色卫星数据的重构方法——DINEOF-G。利用此方法对杭州湾2017年的GOCI总悬浮物质量浓度数据进行重构,结果表明该方法相比经典方法在重构精度上提高了8%,数据重构率提高了36%,且重构结果较好地反映了杭州湾总悬浮物质量浓度的季节变化规律和空间分布特征。     

赤道东印度洋和孟加拉湾障碍层厚度的季节内和准半年变化

利用2002—2015年ARGO网格化的温度、盐度数据, 结合卫星资料揭示了赤道东印度洋和孟加拉湾障碍层厚度的季节内和准半年变化特征, 探讨了其变化机制。结果表明, 障碍层厚度变化的两个高值区域出现在赤道东印度洋和孟加拉湾北部。在赤道区域, 障碍层同时受到等温层和混合层变化的影响, 5—7月和11—1月受西风驱动, Wyrtki急流携带阿拉伯海的高盐水与表层的淡水形成盐度层结, 同时西风驱动的下沉Kelvin波加深了等温层, 混合层与等温层分离, 障碍层形成。在湾内, 充沛的降雨和径流带来的大量淡水产生很强的盐度层结, 混合层全年都非常浅, 障碍层季节内变化和准半年变化主要受等温层深度变化的影响。上述两个区域障碍层变化存在关联, 季节内和准半年周期的赤道纬向风驱动的波动过程是它们存在联系的根本原因。赤道东印度洋地区的西风(东风)强迫出向东传的下沉(上升)的Kelvin波, 在苏门答腊岛西岸转变为沿岸Kelvin波向北传到孟加拉湾的东边界和北边界, 并且在缅甸的伊洛瓦底江三角洲顶部(95°E, 16°N)激发出向西的Rossby波, 造成湾内等温层深度的正(负)异常, 波动传播的速度决定了湾内的变化过程滞后于赤道区域1~2个月。     

三亚湾浮游动物数量分布及群落特征的季节变化

根据三亚湾2005年春、夏、秋和冬季航次的调查资料,分析了这4个季度的浮游动物的种类组成、优势种、群落结构、丰度和生物量的时空变化。经过鉴定共有终生性浮游动物125种,阶段性浮游动物17种,其中毛颚类幼虫和短尾溞状幼虫是各个季度都出现的优势种。三亚湾的浮游动物可以分为河口类群、暖水沿岸类群和广布暖水外海类群。全年浮游动物平均丰度为95.91ind·m-3,浮游动物平均生物量为69.22mg·m-3;浮游动物丰度的季节分布是夏>秋>春>冬,平均生物量的季节分布是秋>夏>春>冬,总体上一般是夏秋季高于冬春季。冬季浮游动物丰度与浮游植物细胞总密度之间没有相关性。     

ECOMSED模式在杭州湾海域流场模拟中的应用

针对杭州湾独特的喇叭型强潮河口湾的特点,基于Blumberg等(1996)的ECOMSED模式,引入动边界技术,建立杭州湾三维动边界的潮流模型.模型以正交曲线坐标下三维非线性水动力方程为基本方程,应用Mellor和Yamada的2.5阶湍流闭合模型计算紊动黏滞系数,嵌入Grant和Madsen的底边界层模型考虑波浪对底部应力的作用,采用干湿网格法模拟潮流漫滩过程;综合考虑径流,风应力,密度流和M₂,S₂,K₁,O₁四个主要分潮和M₄,S₄,MS₄三个浅水分潮的作用,从而提高杭州湾潮流模拟的精度.通过验潮站调和常数和多次海流连续观测资料的验证,表明该文建立的模型可以更好的用于杭州湾流场的预报模拟.     

渤海湾表层沉积物重金属与污染评价

用原子吸收法测定了渤海湾表层沉积物中重金属的含量,同时用2种评价方法对该海域底质环境进行了评价。结果表明:沉积物中汞、锌含量平均值超过标准,其余项目未发现超标;其分布特征由于受沿岸不同污染源的污染影响,重金属污染物难以形成一定规律的分布状态。同时该海域底质环境质量总指数已达到污染程度和很强的生态危害,其中主要污染元素是Hg,已达重污染,并形成极强的生态危害。     

辽东湾北部海域营养状况与趋势评价

根据 1999-2006 年 6-8 月的调查数据,分析辽东湾北部海域的营养水平及变化趋势,以了解辽东湾北部海域营养水平的分布特点及污染状况.由 E 值和 CN/CP 值的总体评价结果来看,辽河口、双台子河口和大凌河口海域的富营养化程度较高,属于磷中等限制潜在性富营养区,而锦州湾海域污染相对较轻,属于中度营养区;在时空分布上,辽东湾北部海域 1999 年与 2006 年污染较为严重,中间年份污染相对较轻.针对辽东湾的具体环境用 CN/CP 值的评价模式更能揭示出营养盐限制对富营养化的影响.     

Preliminary study on different nutrient pools supplies for the phytoplankton growth in the Jiaozhou Bay in China in the fall of 2004

The source and significance of two nutrients, nitrogen and phosphorous, were investigated by a modified dilution method performed on seawater samples from the Jiaozhou Bay, in autumn 2004. This modified dilution method accounted for the phytoplankton growth rate, microzooplankton grazing mortality rate, the internal and external nutrient pools, as well as nutrient supplied through remineralization by microzooplankton. The results indicated that the phytoplankton net growth rate increased in turn from inside the bay, to outside the bay, to in the Xiaogang Harbor. The phytoplankton maximum growth rates and microzooplankton grazing mortality rates were 1.14 and 0.92 d-1 outside the bay, 0.42 and 0.32 d-1 inside the bay and 0.98 and 0.62 d-1 in the harbor respectively. Outside the bay, the remineralized nitrogen (Kr=24.49) had heavy influence on the growth of the phytoplankton. Inside the bay, the remineralized phosphorus(Kr=3.49) strongly affected the phytoplankton growth. In the harbor, the remineralized phosphorus (Kr=3.73) was in larger demand by phytoplankton growth. The results demonstrated that the different nutrients pools supplied for phytoplankton growth were greatly in accordance with the phytoplankton community structure, microzooplankton grazing mortality rates and environmental conditions. It is revealed that nutrient remineralization is much more important for the phytoplankton growth in the Jiaozhou Bay than previously believed.