A three-layer model for the thermal structure in the Huanghai Sea

A one-dimentional three-layer model for the thermal structure in the Huanghai Sea is presented in this study, me model consists of the upper mixed layer caused by heating and wind mixing, the lower mixed layer driven by tidal mixing, and the thermocline with certain thickness. The entrainment velocities of the upper and lower layers are obtained respectively. The results show that the model is capable of describing the development and decline processes of the seasonal thermocline in the Huanghai Sea, simulating successfully the Huanghai Sea Cold Water Mass, the nearshore front and surface cold water off North Jiangsu and explaining reasonably their formation mechanisms as well as the strong thermocline off Qingdao. It is suggested that the tidal mixing plays key role in the formation of the nearshore front off North Jiangsu and the strong thermocline off Qingdao. The wind mixing and the tidal mixing make the lower layer water with high nutrients go up to the upper layer. This physical process may be sig     

Cross thermocline mixing effect due to tide in the shallow sea

Using the data specially observed on the Bohai Sea oil platform by the authors for studying thermocline for two weeks, the thermocline depth, the temperature and the salinity of the layers below and above the thermocline were numerically modelled. The model is based on the Stigebrandt model and some important supplements are made in this paper in accordance with the local condition of the sea. The modelling results fit well in the observations. It is proved that the entrainmem due to both the tide and the wind can give rise to rather intense mixing cross the thermocline. This process makes the temperature rising below the thermocline,and causes the nutrient increasing above it,which has important significance for the marine physical environment and the marine organism.     

海浪混合参数化的渤海、黄海、东海水动力环境数值模拟

在浪-流耦合的概念下,对Princeton Ocean Model(POM)模式进行改进,增加特征波参数下的海浪混合作用,并把潮流和环流同时模拟,得到了渤海、黄海、东海典型的环流和水文特征,特别是夏季黄海的温跃层现象,夏季长江冲淡水扩展路径以及我国东部海域冬季和夏季典型环流等.研究表明,海浪的作用使海洋上层混合得更均匀,潮流的作用使海洋底层混合得更均匀,二者是温跃层形成的重要原因;考虑潮效应模拟流场,由于潮扩散和潮余流的作用,长江冲淡水路径与实际观测更为符合.     

Basic characteristics and forming mechanism of the sharp thermocline in the Bohai Sea, Huanghai Sea and northern East China Sea

- On the basis of the fact that the sharp thermocHne in the Bohai Sea and the northern Huanghai Sea is often distributed in the deep valley areas, it has been long thought that the reason of the formation of the sharp thermocHne is that the cold water can be easily kept in valleys. But recent investigations carried out in the southern Huanghai Sea in summer show that all of the sharp thermocHne areas were distributed in the shallow sloping-bottom areas but not in the deep valley areas. Only in autumn would the sharp thermoclines translate to the deep valley areas. In summer, they are characterized by shallow upper mixing layer and thin thickness in the southern Huanghai Sea. In addition to entrainment coming from lower boundary of upper mixing layer the entrainment from upper border of bottom homogeneous layer induced by tidal mixing also plays an important role in the growth and decay of thermoclines in these seas.     

冬季寒潮期间黄、渤海水位低频波动研究

利用 POM(Princeton Ocean Model)海洋数值模式建立渤、黄、东海冬季三维环流动力学区域模型。模型在海-气边界使用包括风应力、气压和热通量的大气驱动, 海洋边界使用西太平洋模式提供的环流和潮位驱动, 综合模拟潮波运动、温度、盐度、环流变化和水位低频波动。 模拟了 2001 年 1 月寒潮过境时黄、 渤海水位低频波动及流场变化, 分析了其对大风过程、 气压、降温的响应, 发现冬季强劲的北风和西北风都可以通过抽吸振荡在渤、 黄海诱发水位的低频波动, 东北风则由于地形影响不能诱发渤、黄海的低频波动。气压和降温只是在波动幅度上有一定的影响。波动发源于渤海和北黄海, 最大波幅可以达到 0.6 m。波动进入南黄海后有沿黄海深槽西侧传播的倾向, 波动幅度在传播过程中逐渐减小。     

渤海悬浮物分布的遥感研究

利用渤海湾和莱州湾现场实测的悬浮物含量和光谱数据,建立了基于555和670nm波段遥感反射率的悬浮物含量遥感反演模型。经检验,模型平均相对误差优于20%,对输入端误差不敏感。基于该模型,利用ENVISAT MERIS遥感数据,从空间分布格局、大风过程的短期扰动以及季节性差异等方面分析了渤海悬浮物的时空分布特征。(1)渤海悬浮物含量的高值区集中分布在莱州湾(尤其是黄河口和莱州湾湾底)和渤海湾沿岸,此外在辽东湾沿岸海域悬浮物含量也相对较高,而在渤海大部水体悬浮物含量较低。(2)大风过程可在短期内(约1~3d)显著改变全渤海的悬浮物空间分布格局,其中渤海湾和莱州湾响应最为强烈,辽东湾响应相对较弱,这与其各自的水深条件、底质类型和悬浮物粒径等因素有关。(3)渤海悬浮物含量总体上呈春夏低、秋冬高的分布特征;季节性差异最显著的区域是渤海湾、莱州湾和辽东湾,差异性最小的是秦皇岛近岸海域;风力等气候因素是悬浮物分布呈现季节性差异的主要原因,入海径流是另一重要因素。     

潮汐作用下渤海温跃层波动与起伏的数值研究

研究了潮汐(四大分潮 M₂,S₂,K₁,O₁同时输入)作用下渤海温跃层起伏与波动的三维数值模型(将海洋分为3层,即上混和层、跃层和下混和层),揭示了整个海区温跃层上界面处跃层起伏(在文中指每个时刻跃层波高的周期平均值)的地理分布及叠加在起伏之上的潮周期波动的时空变化,模拟出跃层波动与实测基本一致.结果发现大振幅的跃层波动均发生在海峡及近海地形突变之处.一般界面波动的波高大于甚至远远大于同一位置的表层潮波.从位相以及周期来看,潮波和跃层上下界面波动相互之间,有些海域一致,有些地方则相差甚远.跃层上界深度及厚度的梯度,对跃层起伏分布有一定的影响.跃层起伏还可能与海岸海底摩擦有关.     

Exploring the thermal cycle of the Northern North Sea area using a 3-D circulation model: the example of PROVESS NNS station

Within the framework of activities of the EC funded Project ‘Processes of Vertical Exchange in Shelf Seas’ (PROVESS), the seasonal thermal behaviour during 1998 at a station in the North Sea has been investigated using COHERENS, a three-dimensional fully non-linear hydrodynamic model. Extensive hydrographic measurements were carried out at the Northern North Sea (NNS) station, located at (59°20′N, 1°E). The collected data are used to validate the model results, showing an acceptable agreement between modelled temperatures and those obtained from CTDs and moored thermistors. This is valid both for surface and bottom temperatures, while the mixed layer thickness appears to be underestimated. A series of 3-D runs, testing different turbulence schemes, an internal wave mixing (IWM) parameterisation and the sensitivity to an increase of the surface stress, have been performed with the aim of assessing the relative importance of the advective and mixing processes. The model comparisons mostly evidenced differences in the behaviour of the bottom layer temperature during the last part of the year, which may be due to advection processes. The adoption of an internal wave mixing parameterisation, though managing to reproduce a deeper thermocline, overestimates the mixing around the period of the thermocline breakdown. The run adopting a wind stress increased by 50% provides a better agreement between observed and modelled thermocline. This applies also for surface velocities when compared to Acoustic Doppler Current Profiler (ADCP) measurements, while the bottom ones appear slightly underestimated only in the U-component. The Northern North Sea site appears to be located close to a gyre induced by thermal fronts. Comparisons with nearby wind data measured by an oil rig and by the ships operating in the area seem to confirm that the wind forcing values adopted during the integration are underestimated.     

渤海重现期波高的数值计算

利用RAMS大气模式给出的20年风场资料,利用SWAN近海波浪模式对渤海海域的波浪进行了20 a数值计算.通过与一般过程和大风过程的实测资料的对比后发现.波浪模拟值与实潮值符合地较好,SWAN模式适合渤海海域波浪的计算。通过分析发现.辽东湾常浪向为SSW。强浪向为SSW;渤海中部常浪向为S,强浪向为NE;渤海海峡常浪向为NNW,强浪向为NNW;莱州湾常浪向为S,强浪向为NNE;渤海湾常浪向为S.强浪向为NE。渤中偏东南海域(38°～39°N,119.5°～120.5°E)多年一遇有效波高最大.其中百年一遇有效波高最大值达到6.7m。     

渤、黄海风生流场季节循环时空模态与变异

根据1978—2015年渤、黄海沿岸观测风应力场与二维非线性垂直平均风生流模式，以及旋转经验正交函数（REOF）、调和分析等方法，研究了渤、黄海月平均风生流速度势、流函数场季节循环时空模态与年际变异.渤、黄海月平均风生流速度势、流函数场主要有两种时空模态，季节周期分量是时空模态的主要分量.由于风应力场季节循环变异，渤海流函数场季节时空循环变异程度大于速度势场，速度势、流函数场第二模态是季节变异的主要分量，黄海速度势场季节时空循环变异程度大于流函数场，速度势场第二模态是季节变异的主要分量.由于月平均风应力场强度年际变化显著线性减弱，渤、黄海季节平均风生流场强度年际变化也显著减弱.渤、黄海暖流与冷水团季节生消是风生流水平环流与垂直对流对冷 暖水体输送与汇集共同作用的结果，渤、黄海春、夏季辐合上升环流延缓及减弱了浅层暖水向深层传播，是春、夏季冷水团与温跃层形成的重要动力因素，因此，速度势是研究渤、黄海风生流场十分重要的因素.冬季渤海中部、黄海东部反气旋型及辐散下沉环流与黄海中部气旋型环流、辐合上升环流是黄海暖流季节转换与强度的主要动力控制因素，夏季黄海东部气旋型环流、辐合上升环流与黄海中部反气旋型环流、辐散下沉环流是黄海冷水团季节转换与强度的主要动力控制因素.     

Annual cycle of stratification and tidal fronts in the Bohai Sea: A model study

In general, competition between buoyancy mechanisms and mixing dynamics largely determines the water column structure in a shelf sea. A three dimensional baroclinic ocean model forced by surface heat fluxes and the 2.5 order Mellor-Yamada turbulence scheme is used to simulate the annual cycle of the temperature in the Bohai Sea. The difference between the sea surface temperature (SST) and sea bottom temperature (SBT) is used to examine the evolution of its vertical stratification. It is found that the water column is well-mixed from October to March and that the seasonal thermocline appears in April, peaks in July and then weakens afterwards, closely following the heat budget. In addition, the Loder parameter based on the topography and tidal current amplitude is also computed in order to examine tidal fronts in the BS, which are evident in summer months when the wind stirring mechanism is weak.     

The preliminary study of the high chlorophyll in the central Bohai Sea in summer

In the central Bohai Sea, both historical data and in situ observations show that the distribution of high chlorophyll concentration is consistent with warm water. The previous studies confirm that the warm water is caused by a joint effect of wave and tidal mixing. In this paper, the authors have coupled the Princeton ocean model (POM) with a biochemical model to further investigate the formation of the high chlorophyll concentration. When the wave mixing is excluded, the water temperature is lower and the chlorophyll concentration is also lower than the observation. However, if the wave mixing is included, strong wave mixing in the upper layer brings the warm water downward and nutrients upward so that both temperature and nutrients tend to be uniformly high from the surface to the bottom. This provides an environment which is favorable for the growth of the phytoplankton. Therefore the chlorophyll concentration, as a symbol of phytoplankton, shows high value in the central Bohai Sea. In conclusion, the wave mixing plays an important role in the formation of high chlorophyll concentration in the central Bohai Sea.     

声跃层控制声线传播弯曲模型的构建

基于斯涅耳折射定律,将海水垂向等分成若干层,利用傅里叶步近算法,构建受声速剖面唯一控制的声线传播弯曲模型。将该模型用于模拟研究不同浅海声跃层类型对声线传播弯曲的影响,得出声线波长和轨迹长度按负跃层、无跃层、正跃层的顺序逐渐增加。并利用该模型定量研究跃层深度、跃层强度、跃层厚度三特征参量对声线传播弯曲的影响,得出负跃层强度越大、厚度越大、深度越浅,声线弯曲越大,波长越小。正跃层三特征参量对声线作用相反。     

渤海夏季潮致-风生-热盐环流的数值诊断计算

基于正交曲线坐标的ECOMSED三维水动力模式,并考虑了潮汐、风和实测温盐场,诊断计算了渤海夏季三维潮致-风生-热盐环流,分析了渤海夏季潮致余流、风生和热盐环流的分布结构。结果显示,在夏季,渤海中部海区明显存在一个顺时针向的涡旋,同时渤海还存在着多个逆时针向的涡旋。通过分析和比较各个分量在总环流中的作用,认为夏季潮致余流是相对弱的;热盐环流在夏季总环流中占主要成分。     

A PARAMETRIC MODEL FOR THERMAL STRUCTURE FEATURES OF THE OCEAN UPPER LAYER

Based on the non-dimensional general function for the thermal structure features presented by S. A. Kitaigorodsky et al. (1963, 1965)[10,11]. this paper tries to establish semi-empirical and semi-theoretical models bfor the thickness of the upper homogeneous layer of the ocean, thermocline intensity and lower oundary depth of thermocline by consecutive observations from 159 stations in the Bohai Sea,Huanghai Sea and East China Sea in the warm half of the years from 1957 to 1964 and the heat budget at the sea surface computed with the simplified computing formulae proposed by Wang (1983)[22]. This model indicates the main factors forming the thermal structure features in the upper layer of the ocean and their function. With the model, one can directly use the sea surface temperature, air temperature and wind speed to compute the thermal feature in the upper layer of the ocean.     

秋季和春季黄渤海黄色物质空间分布特征

利用2013年秋季和2014年春季两个季节黄渤海现场数据对黄色物质的水平分布及垂向分布的变化进行研究,并初步分析了其主要控制因素。垂向黄色物质表现为底部高上层低的特征。其中,秋季混合作用加强导致上层40m黄色物质混合较为均匀;春季北黄海温盐跃层已经形成,黄色物质分布开始出现明显的分层现象,上下层浓度差约为2?g/L。春季南黄海盐度跃层尚未形成,水深小于50m的水层黄色物质垂向分布均匀,近岸和远岸海域浓度分界线明显。水平方向上,黄色物质在秋季和春季分布趋势一致,由渤海、北黄海至南黄海浓度依次降低,且呈现出由近岸向中央海区递减的趋势,但整体上春季浓度较秋季明显偏低。海表盐度与黄色物质浓度两者整体上呈现负相关关系,可以将黄色物质浓度分布作为研究黄海暖流走向、划分水团性质的重要指标。     

2016年春季浙江中部海域温、盐、密度的断面分布特征

厦门大学海洋与地球学院，近海海洋环境科学国家重点实验室。摘要：本文通过分析2016年春季航次在浙江中部海域3条断面的观测资料，结果表明：（1）在断面的10~25米层左右观测到了"中层冷水"现象以及在上层观测到微弱的上升流；（2）在浙江中部海域的上层观测到较弱的上升流；（3）春季，在浙江中部海域观测到了丰富的温跃层、逆温跃层以及盐跃层现象。（4）台湾暖流水向上爬坡对跃层的变化有一定的影响，使得跃层厚度变小，跃层强度加强，但是强度并不足以冲破跃层到达表层。     

A numerical study of transport dynamics and seasonal variability of the Yellow River sediment in the Bohai and Yellow seas

A sediment numerical model was embedded into a wave-tide-circulation coupled model to simulate the transport processes of the Yellow River-derived sediment considering the wave-induced vertical mixing (Bv) and the wave-current coupled bottom shear stress (BSS). Numerical results show that the main stream of the Yellow River-derived sediment moves first eastward off the northern Shandong Peninsula and then southward into the South Yellow Sea all year round. In spring, the sediment moves northeastward in the Bohai Sea. In summer, there is a northeastward branch of sediment in the Bohai Sea off the west coast of the Liaodong Peninsula, while the main part goes eastward to the Yellow Sea. The Yellow River-derived sediment transport from the Bohai Sea to the North Yellow Sea across the Bohai Strait is mainly limited to the top 10 m, and with a maximum centered at 37.9°N in summer. The transport from the North Yellow Sea to the South Yellow Sea across the transect of 37°N is mainly in the 0–30 m layer with a maximum around 123.7°E in autumn. The simulated Yellow River-discharged sediment deposits along the Shandong Peninsula and between 20 and 30 m isobaths in the Yellow Sea, which is consistent with observation. If surface waves are not considered in the model, the sediment deposits westward to the nearshore area in the South Yellow Sea. The sediment would deposit further southward in the numerical experiment results without wind influence. In the numerical experiment of no tide, there is hardly any sediment deposited on the Yellow Sea floor, while in the Bohai Sea most of the sediment is transported southward and northwestward around the river mouth instead of eastward as in the Control Run, indicating the tides play a key role in forming the deposition pattern.     

渤海、黄海热结构分析

在多年观测资料基础上,以月平均风应力和周平均海表水温(SST)作为外强迫,对黄海、渤海热结构进行了数值模拟.模拟结果显示渤海的热结构特征自10月至翌年3月为水温垂直均一的冬季型;5～8月为分层结构(由上混合层、跃层、潮混合层组成)的夏季型.4月和9月为两型的过渡期,最低水温出现在2月,最高水温表层出现在8月,底层则在9～10月.黄海沿岸浅水区与渤海有相似的热结构,黄海冷水团和黄海暖流对其中央槽深水区的热结构有重要影响.对底层水的影响而言,前者夏季显著而后者冬季显著,从而导致黄海(槽)的底层水与环境相比呈现夏季冷而冬季暖的特征,底层水温基本上与表面水温的年变化反相;深水区的热结构与渤海相比,均一型结构(1～3月)变短,分层型结构(5～11月)变长,底温年变幅(5℃以内)变小,跃层强度增强.模拟结果还表明,黄海暖流的动力仍然是季风环流,而对黄海冷水团的形成和发展有无动力影响提出质疑.     

北黄海温盐分布季节变化特征分析

利用2006～2007年夏冬春秋4个季节北黄海的大面调查资料,分析了4个季节北黄海温度和盐度大面以及典型断面分布特征,得出以下结论:2007年冷水团势力范围强于2006年,北黄海冷水团的形成受地形影响.黄海暖流冬春季较强,冬季最强,夏季最弱,秋季开始形成.鲁北沿岸流冬季最强,春季减弱,夏秋季消失,但夏季鲁北沿岸存在冬季鲁北沿岸流水的残余体,即鲁北沿岸水.辽南沿岸水4个季节都以低盐为特征,除夏季低盐中心位于庄河口外,其它3个季节低盐中心均位于调查区域的东北角.渤海与北黄海之间的水交换4个季节都存在.春季,断面盐跃层形成滞后于温跃层;秋季,断面盐跃层消失滞后于温跃层.