南海北部相干内潮和非相干内潮演变特征

通过南海北部跨越陆坡和陆架区的3套潜标数据,对全日和半日相干、非相干内潮的动能变化特征进行了研究。研究表明,全日内潮沿陆坡区向陆架区传播的过程中,在陆坡区主要以全日相干内潮生成为主,平均动能生成率为2.32 J/（m3·s）;在陆架区以全日相干内潮耗散为主,平均动能耗散率为0.44 J/（m3·s）。全日非相干内潮动能在陆坡和陆架区均增长,平均动能生成率分别为0.39 J/（m3·s）和0.03 J/（m3·s）。全日与半日相干内潮动能在陆坡和陆架区的表现不同,陆坡区的全日相干内潮动能明显大于陆架区的全日相干内潮动能,而半日相干内潮动能在陆坡和陆架区没有明显差别;陆架区的全日和半日非相干内潮动能要大于陆坡区的全日和半日非相干内潮动能。     

南海东北部全日非相干内潮的特征及其成因

本文利用南海东北部的潜标资料研究了南海东北部全日非相干内潮的特征。潜标数据的结果表明,在2010年7月下旬和8月上旬,全日非相干内潮的能量显著增强,同时全日内潮的总能量强度达到了预期(相干部分)的两倍;从能量的垂向分布上来看,非相干内潮的能量最大值出现在120 m深度附近。射线追踪模型的结果表明,此次强非相干内潮能量主要来自吕宋海峡的中部,黑潮入侵是导致非相干内潮信号增强的主要原因,全日内潮在吕宋海峡中部生成后向西传播进入南海,而黑潮改变了全日内潮的传播路径,将西向传播的内潮向北折射,导致来自多源地的内潮在潜标处叠加,引起全日非相干内潮能量的增强。本文的结果将有助于加深对非相干内潮的特征的认识和促进对其生成机制的了解。     

基于浮标观测的南海西沙群岛潟湖区潮流特征研究

本文利用南海西沙群岛潟湖区29 d的全水深浮标观测资料研究了潟湖区内正压潮和内潮的基本特征,采用深度平均方法分析海流的适用性,并讨论潟湖区内潮的主要来源。深度平均流的动能谱显示全日潮流占主导,其动能占整体海流动能的41%。对比分析深度平均流和Tpxo7.2模式预测的全日、半日潮流的调和常数,两者均表明全日正压潮流受地形调制,主轴方向为西北-东南向,而半日正压潮流主轴方向为东-西向。两种方法得到的全日正压潮流大-小潮存在半个相位（6～7 d）的差异,进一步分析发现全日正压潮和全日内潮潮龄不同,存在部分相互抵消,且全日内潮大潮发生时间在深度上存在差异,推测由于缺少海表和海底的测量数据,导致深度平均方法得到的全日正压潮仍然包含全日内潮信号。调和分析结果表明,全日内潮的动能中相干部分占比高达91%,说明潟湖区的全日内潮是正压潮与局地岛礁地形相互作用产生,而从远场传播而来的可能性很小。     

大亚湾冬季海流波动的分析

本文以实测资料为依据,利用时间序列功率谱的方法,分析大亚湾湾口冬季的海流波动特点,得出了本海域海流波动是以半日分潮潮流为主的半日分潮、全日分潮和浅海分潮潮流共存的波动形式,其振幅表层大于底层等结论。文中还指出了半日分潮、全日分潮和浅海分潮潮流波动振幅变化的特征。     

黑潮对吕宋海峡全日内潮生成与传播影响的数值模拟研究

基于一套环流-潮汐耦合模型的模拟结果,本文探究并比较了2015—2016年的三种黑潮形态下,吕宋海峡全日内潮以及全日非相干内潮生成与传播的空间分布特征。结果表明,当黑潮以流套形态流经吕宋海峡时,全日内潮非相干性最强,具体表现为全日非相干内潮能量生成最大,全日内潮的传播速度变化率最大。由于传播速度的变化会改变全日内潮的位相,进而会影响全日内潮的非相干性,导致在吕宋海峡内全日内潮的非相干性最强。本研究结果对理解黑潮背景动力过程下吕宋海峡内潮的时空变化有重要意义。     

广西近岸西部海域的海流特征研究

利用广西近岸西部白龙半岛海域2011—2012年连续一年的观测资料和数值计算方法,研究了该海域潮流和余流的基本特征及变化规律,得出如下结论:白龙半岛海域潮汐为正规全日潮,但是潮流为不规则半日潮流;旋转谱分析显示,潮流逆时针旋转分量强于顺时针旋转分量,全日潮流的总能量小于半日潮流的能量;潮流振幅在夏季明显高于冬季,这是因为夏季北部湾北部的显著层结导致的较浅海域的内潮同样比较显著,并且表现为由表层向底层加强;另外,本文首次发现,经过北部湾的台风会增强主要的全日、半日分潮的能量,引起潮流的流速增加。通过数模试验,第一次发现在白龙半岛附近海域存在一个小尺度的反气旋涡,范围大约位于108°E~108.7°E、20.8°N~21.5°N,涡旋在秋季产生,可以一直持续到冬季结束。     

马六甲海峡的潮汐特征分析

马六甲海峡是亚洲东南部的重要海峡通道,沟通太平洋和印度洋,具有重要的经济和战略地位.本文利用马六甲海峡及其毗邻海域验潮站的实测水位资料,分析了马六甲海峡及马来半岛东岸的潮汐特征.研究表明,半日分潮平均振幅最大的区域位于马六甲海峡内部,而全日分潮平均振幅最大的区域为马来半岛的东海岸.马六甲海峡内部以正规半日潮为主,马来半岛东侧则为混合潮港,北部为不正规全日潮,南部则为不规则半日潮.半日分潮M2,S2和全日分潮K1在马六甲海峡内的传播为自西北向东南,而全日分潮O1则为自东南向西北方向.马来半岛东岸的半日潮传播方向以中部的Cendering站为分界线,南、北两部海区分别向南、向北相背传播,而全日潮传播方向相同,统一为自北向南.     

南麂岛附近海域潮汐和潮流的特征

以2008年冬季在浙江近海南麂岛附近投放的4个底锚系观测的水位和流速资料为依据,分析了潮汐和潮流特征。水位谱分析结果显示半日分潮最显著,全日分潮其次;近岸的浅水分潮比离岸大。水位调和分析结果表明:潮汐类型均为正规半日潮,近岸处的平均潮差大于3m,最大可能潮差大于6m,潮汐呈现出显著的低潮日不等和回归潮特征。流速谱分析结果显示半日分潮流最强,全日分潮流其次,且比半日分潮流小得多;近岸浅水分潮流比远离岸显著。流速调和分析结果表明:潮流类型均为正规半日潮流,靠近岸的两个站浅水分潮流较显著;最显著的半日分潮流是M2分潮流,其最大流速介于0.32～0.48m/s之间,全日分潮流均很弱,最大流速小于0.06m/s。M2分潮流均为逆时针旋转,椭圆率越靠近海底越大;最大分潮流流速分布为中上层最大、表层略小、底层最小;最大分潮流流速方向的垂向变化很小,底层比表层略为偏左;最大分潮流流速到达时间随深度的加深而提前,底层比中上层约提前30min。潮流椭圆的垂向分布显示这里的半日分潮流以正压潮流为主;日分潮流则表现出很强的斜压性。     

基于潜标观测的吕宋海峡以东深海潮流特征研究

本文使用吕宋海峡以东的潜标观测的长达1年的海流数据,重点对该海域海流的高频波动(潮流)的垂向分布及其时间变化特征进行了分析,结果表明:该海域次表层(100～160 m)的潮动能比中层(1 550 m)和深层(2 560 m)大1～2个数量级,近底层(4 040 m)的潮动能略大于中、深层;次表层为不正规半日潮流,中、深层为不正规全日潮流;各层次潮动能均在夏季(6?9月)和冬季(2?3月)增强,与M₂分潮和K₁分潮在夏季和冬季的增强相对应;各层次海流的高频波动以顺时针旋转为主,次表层海流近惯性周期接近当地理论惯性周期,中、深层略小于当地理论惯性周期。     

基于数值模式的南海北部深层内潮季节变化特征分析

本文基于MITgcm非静力数值模式,采用实际地形、层结和潮流强迫,开展南海北部内潮数值模拟敏感性试验,分析夏冬两个季节南海北部深层内潮的差异。结果显示在南海北部深层,冬季K₁和M₂内潮流速振幅比夏季强10.1%和44.7%。垂向模态分析结果进一步表明,尽管南海北部深层冬季第一模态内潮动能密度比夏季低15.5%,但第二和第三模态内潮则是冬季比夏季高约25.1%和33.2%,导致冬季深层流速的垂向剪切大于夏季,表明冬季较强的高模态内潮可能是冬季南海深层强混合的一个原因。     

南海北部东沙岛附近海洋底层流场特征及时间变化规律

Near-bottom currents play important roles in the formation and dynamics of deep-water sedimentary systems.This study examined the characteristics and temporal variations of near-bottom currents, especially the tidal components, based on two campaigns(2014 and 2016) of in situ observations conducted southeast of the Dongsha Island in the South China Sea. Results demonstrated near-bottom currents are dominated by tidal currents, the variance of which could account for ～70% of the total current variance. Diurnal tidal currents were found stronger than semidiurnal currents for both barotropic and baroclinic components. The diurnal tidal currents were found polarized with predominantly clockwise-rotating constituents, whereas the clockwise and counterclockwise constituents were found comparable for semidiurnal tidal currents. It was established that diurnal tidal currents could induce strong current shear. Baroclinic tidal currents showed pronounced seasonal variation with large magnitude in winter and summer and weak magnitude in spring and autumn in 2014. The coherent components accounted for ～65% and ～50% of the diurnal and semidiurnal tidal current variances,respectively. The proportions of the coherent and incoherent components changed little in different seasons. In addition to tidal currents, it was determined that the passing of mesoscale eddies could induce strong nearbottom currents that have considerable influence on the deep circulation.     

南海西北部半日内潮参量次谐频不稳定生成的近惯性波研究

为了研究非临界纬度上参量次谐频不稳定(parametric subharmonic instability,PSI)过程生成的近惯性波(near-inertial wave,NIW),本文基于国家重点研发项目的 准实时传输深海潜标资料,对内波速度谱、近惯性流速和动能、D2-f(半日频减惯性频)流速和动能、半日内潮流速和...     

沿海观测站海表温度质量控制和半日特征分析

Sea surface temperature(SST) data obtained from coastal stations in Jiangsu, China during 2010–2014 are quality controlled before analysis of their characteristic semidiurnal and seasonal cycles, including the correlation with the variation of the tide. Quality control of data includes the validation of extreme values and checking of hourly values based on temporally adjacent data points, with 0.15°C/h considered a suitable threshold for detecting abnormal values. The diurnal variation amplitude of the SST data is greater in spring and summer than in autumn and winter. The diurnal variation of SST has bimodal structure on most days, i.e., SST has a significant semidiurnal cycle. Moreover, the semidiurnal cycle of SST is negatively correlated with the tidal data from March to August, but positively correlated with the tidal data from October to January. Little correlation is detected in the remaining months because of the weak coastal–offshore SST gradients. The quality control and understanding of coastal SST data are particularly relevant with regard to the validation of indirect measurements such as satellitederived data.     

南海东北部内潮的模态结构和传播

The evolution of energy, energy flux and modal structure of the internal tides(ITs) in the northeastern South China Sea is examined using the measurements at two moorings along a cross-slope section from the deep continental slope to the shallow continental shelf. The energy of both diurnal and semidiurnal ITs clearly shows a～14-day spring-neap cycle, but their phases lag that of barotropic tides, indicating that ITs are not generated on the continental slope. Observations of internal tidal energy flux suggest that they may be generated at the Luzon Strait and propagate west-northwest to the continental slope in the northwestern SCS. Because the continental slope is critical-supercritical with respect to diurnal ITs, about 4.6 kJ/m~2 of the incident energy and 8.7 kW/m of energy flux of diurnal ITs are reduced from the continental slope to the continental shelf. In contrast, the semidiurnal internal tides enter the shelf because of the sub-critical topography with respect to semidiurnal ITs.From the continental slope to the shelf, the vertical structure of diurnal ITs shows significant variation, with dominant Mode 1 on the deep slope and dominant higher modes on the shelf. On the contrary, the vertical structure of the semidiurnal ITs is stable, with dominant Mode 1.     

Numerical study of baroclinic tides in Luzon Strait

The spatial and temporal variations of baroclinic tides in the Luzon Strait (LS) are investigated using a three-dimensional tide model driven by four principal constituents, O₁, K₁, M₂ and S₂, individually or together with seasonal mean summer or winter stratifications as the initial field. Barotropic tides propagate predominantly westward from the Pacific Ocean, impinge on two prominent north-south running submarine ridges in LS, and generate strong baroclinic tides propagating into both the South China Sea (SCS) and the Pacific Ocean. Strong baroclinic tides, ∼19 GW for diurnal tides and ∼11 GW for semidiurnal tides, are excited on both the east ridge (70%) and the west ridge (30%). The barotropic to baroclinic energy conversion rate reaches 30% for diurnal tides and ∼20% for semidiurnal tides. Diurnal (O₁ and K₁) and semidiurnal (M₂) baroclinic tides have a comparable depth-integrated energy flux 10–20 kW m⁻¹ emanating from the LS into the SCS and the Pacific basin. The spring-neap averaged, meridionally integrated baroclinic tidal energy flux is ∼7 GW into the SCS and ∼6 GW into the Pacific Ocean, representing one of the strongest baroclinic tidal energy flux regimes in the World Ocean. About 18 GW of baroclinic tidal energy, ∼50% of that generated in the LS, is lost locally, which is more than five times that estimated in the vicinity of the Hawaiian ridge. The strong westward-propagating semidiurnal baroclinic tidal energy flux is likely the energy source for the large-amplitude nonlinear internal waves found in the SCS. The baroclinic tidal energy generation, energy fluxes, and energy dissipation rates in the spring tide are about five times those in the neap tide; while there is no significant seasonal variation of energetics, but the propagation speed of baroclinic tide is about 10% faster in summer than in winter. Within the LS, the average turbulence kinetic energy dissipation rate is O(10⁻⁷) W kg^{− 1} and the turbulence diffusivity is O(10⁻³) m²s⁻¹, a factor of 100 greater than those in the typical open ocean. This strong turbulence mixing induced by the baroclinic tidal energy dissipation exists in the main path of the Kuroshio and is important in mixing the Pacific Ocean, Kuroshio, and the SCS waters.     

基于潜标观测的黑潮-亲潮混合区近惯性能量季节变化特征研究

近惯性内波广泛存在于全球海洋,是维持深层海洋跨等密度面湍流混合及海洋层结的重要能量来源。基于黑潮-亲潮混合区的多年深海潜标数据,分析了:(1)该海域近惯性内波及其能量的季节变化特征与影响因素,(2)上层和深层近惯性运动的频率、波数谱及垂向分布等特征。结果表明,该海域存在丰富的近惯性动能,无论海洋上层还是深层均呈现显著的冬季强、夏季弱的季节变化特征,冬季(12～2月)上层的近惯性能量可占全年能量的41%,深层近惯性信号同样显著,同潮汐信号相当。平板模型分析表明,该区域近惯性动能的季节循环特征主要受风场的季节变化所主导,同时受到黑潮延伸体流轴的摆动调制。     

南海西北陆坡区内潮与近惯性内波观测研究

通过对2006年南海西北部海域近3个月的全水深流速观测资料的分析,研究了该海区正压潮、内潮及近惯性内波的时空分布特征。结果表明,全日内潮明显强于半日内潮,且最大潮流均出现在海洋上层;内潮的主轴方向基本沿东南-西北方向,近似与局地等深线垂直;内潮能量显示出明显的时间长度约为半月的大小潮调制周期;全日内潮的coherent部分占全日内潮能量的70%,而半日内潮的coherent部分占半日内潮能量的53%;进一步研究发现半日内潮主要由第一模态主导,而全日内潮第三模态能量占总能量的比例仅次于第一模态且量值上与之相当;强风过程可激发出强的近惯性运动,暖涡使得近惯性内波能量更有效地向海洋深层传播,冷涡则不利于近惯性内波能量向下传播。     

台湾海峡西侧海湾-岛屿系统影响下的流场年季变化——以南日水道为例

台湾海峡地理位置独特,西侧海域海湾 岛屿系统普遍发育,显著影响了海域流场分布。同时,海峡西岸经济区的快速发展对区域海洋动力环境背景场及其变化的精细认识提出了更高的要求。福建莆田南日岛西侧南日水道是连通兴化湾与平海湾的主要水道,是区域海洋动力环境的“咽喉”所在,在区域海洋环境保护与科学开发利用中居于至关重要的位置。为了全面认识台湾海峡西侧海湾 岛屿系统影响下区域海洋动力环境背景场的年季变化,本研究利用布放在南日水道的座底观测系统获得的周年海流资料,结合同期气象风场资料,通过数据统计分析、调和分析、滤波处理和小波变化等手段,研究了南日水道内海流的季节变化规律和驱动余流的动力要素,初步探讨了热带气旋等对海洋动力演化过程的影响。研究结果表明,研究海域潮流为不正规半日浅海潮流,并具有明显的半月周期,涨潮流大于落潮流,涨潮流主方向为 WNW 向,落潮流主方向为 SE—ESE向。旋转谱结果表明,研究海域以半日潮为主,逆时针能量强于顺时针,惯性周期无明显的谱峰。潮流强度的季节变化特征为冬季最强,秋季、春季次之,夏季最弱。夏、秋季的余流流速较其他季节明显偏大,表层余流有明显的季节特征,底层余流全年为北向流。观测点余流主要由风引起,二者有很好的相关性,但频率统计结果显示二者方向不一致,表明余流在地形的作用下发生了转向,其中潮致余流对表层余流贡献较小。小波能量图表明,双台风（热带气旋）期间风和余流均存在1 d及6 d左右的周期信号,二者密切相关。本研究成果对于区域海洋环保以及海域科学开发与应用具有重要的现实意义。     

川西盆地雾和能见度的气候特征及其对飞行的影响

利用川西盆地广汉机场气象台1986年1月~1995年12月共10 a地面观测资料,对广汉机场低能见度的生消时间、持续时间和能见度的年季节变化及其日变化做了统计分析,研究广汉机场全年能见度的飞行气候特征,特别是低能见度气候特征对飞行的影响。结果表明,能见度日变化特征表现为:白天早、晚时段能见度较低,午后能见度达到最高。能见度的季节变化特征表现为:冬(12,1,2月)、春季(3,4,5月)能见度较低,而夏(6,7,8月)、秋季(9,10,11月)能见度较高。冬季能见度的变化主要受辐射雾影响,夏季能见度的变化主要受降水的影响,随着降水强度的变化而变化,低能见度时间短暂。各标准低能见度逐时频率的日变化特征在各季基本相似,低能见度高频率区均出现在早晨到上午,低频率区均出现在下午。