多源资料重构三维海温场的先验误差估计和诊断分析

针对遥感资料与实况观测融合重构三维海温场的问题，改进了最优插值中的先验统计信息估计，并研究了背景场和观测项的各自影响机制。在最优插值中，将背景场分别取为平均气候场（静态方案）和遥感合成场（动态方案）；在最优融合前，用后验诊断方法迭代优化了背景误差和观测误差协方差；融合完成后，用观测空间诊断误差和模式格点指标对比分析两种方案。主要结论:（1）动态方案相对于静态方案分析误差减小的绝对量值由二者的观测误差之差决定、减小的相对程度由二者的背景误差之比决定；（2）背景场的调整作用在中高纬占优势、在赤道海域与观测项调整作用相当，是由协方差相关尺度的准纬向分布特征决定的；（3）动态分析场的中尺度信号谱能量整体比静态分析场高1~3个量级，但在热带海域相当；（4）遥感资料通过分辨实况观测所无法分辨出来的海温中尺度特征，达到减小误差、提高有效分辨率的效果。     

北印度洋海浪背景误差分析和同化预报初步评估

基于背景误差分析中的观测法,利用Jason-1卫星高度计沿轨有效波高数据并结合Wave Watch Ⅲ海浪模式预报结果,进行北印度洋海域海浪背景误差分析,得到海浪场背景误差方差和各向同性假设下背景误差相关长度的时空分布特征。按经验函数拟合该海域有效波高背景误差协方差时总残差平方和最小的原则给出了更为适用于该海域的描述公式。在上述工作基础上,采用最优插值同化方法将Jason-1和Jason-2卫星高度计有效波高数据连续同化到海浪模式Wave Watch Ⅲ,按业务化标准对2013年1月北印度洋海域的海浪场进行了同化预报试验,经浮标数据检验发现同化可使海浪24 h预报得到明显改进。     

各向异性背景场误差协方差构建及在“凡亚比”台风的应用

利用相临过去时段预报结果中同一时刻不同时效的模式预报场差异,计算预报误差协方差,并基于集合-变分混合同化系统将其与静态背景场误差协方差结合,从而在同化系统中构建了具有各向异性和一定流依赖特征的背景场误差协方差。单点观测理想试验显示本方案改善了静态模型化背景场误差协方差的各向同性和流依赖性问题。“凡亚比”台风的一系列同化及模拟试验表明,从台风路径、强度等方面本文方案的效果都要优于三维变分法。本文方案在不需要集合预报,计算量与三维变分法相当的情况下,给同化系统引入了各向异性、一定流依赖特征的背景误差协方差,因此本方案适于在计算资源较为紧缺情况下,对时效要求较高的预报业务中应用。     

Envisat ASAR海浪谱资料的最优插值同化试验

基于第三代海浪数值模式LAGFD-WAM,分别利用4种不同形式的各向同性背景误差相关函数进行了Envisat高级合成孔径雷达(ASAR)海浪谱资料的最优插值同化试验.与4个浮标实测数据的比较验证表明,ASAR海浪谱资料的最优插值能够有效地改进海浪模式有效波高的模拟.4种不同形式的各向同性背景误差相关函数的同化结果相差不大,决定同化效果好坏的关键是对相关距离尺度的选取.针对自回归形式的背景误差相关函数的试验结果表明,相关距离尺度的量级在400-500km时同化效果最好,此时同化后的模式有效波高均方根误差比未同化时相对减小了26%.     

渤海、黄海、东海冬季海流场温度场数值模拟和同化技术

利用NASA高分辨率的卫星遥感资料SST,采用Nudging同化来模拟渤海、黄海、东海的三维温度场,减小用热通量作上边界条件所带来的误差.结果表明,模拟的海流场能较好地反映渤海、黄海、东海的环流特征.数据同化后的温度场优于未经同化的温度场.3个选择站点的同化值与实测值的均方根误差分别为1.307,0.526,0.744,用热通量资料模拟的水温与实测值的均方根误差分别为2.160,0.979,1.330.尽管只同化了海表温度,但数据同化对三维温度场结构都有影响.     

上海邻近海域风暴潮数据同化与特征分析

风暴潮是一种复杂的对众多因素敏感又备受关注的海洋现象。本文基于协方差局地化的集合卡尔曼滤波方法（EnKF）,选择201810号台风“安比”登陆上海的风暴潮过程,首次将海洋站和FVCOM数值模拟的不同来源、不同误差信息、不同时空分辨率的风暴潮进行数据同化融合,获得了逐72 h的上海海域风暴潮的最优解,进行了同化结果评估验证,并给出了集合样本数和Schur半径设置范围。结果表明,实测计算和数值模拟的风暴增减水之间均方根误差为0.20 m,实测和同化计算的风暴增减水之间均方根误差为0.07 m,准确度提高了65%;独立观测和同化计算的风暴增减水均方根误差为0.09 m,集合离散度与均方根误差比值为0.90,同化效果较好且可信;同化后的风暴增减水能够较好地刻画双峰增水、台风眼增水、增水锋面等特征,对于风暴潮研究、数值模拟结果订正、海洋防灾减灾等有重要意义。     

基于Argo历史观测的南海海盆尺度中层流场研究

针对南海海域海流环境复杂、中层实测数据量少的现状，本文基于2006-2016年布放在南海海域的114个Argo剖面浮标的卫星定位等信息，采用基于背景流和惯性流外推的最小二乘方法，获取南海海域1 200 m深中层流场信息，并采用Divand变分插值的方法形成网格化季节流场。结果表明:（1）针对南海中层（1 200 m）流场，单个Argo浮标可以刻画出具体的中尺度结构，如越南沿岸的反气旋涡，半径约为120 km，最大流速约为9.6 cm/s，平均流速为5.3 cm/s；（2） Argo网格化流场表明海盆尺度中层流场南海南部为反气旋环流结构，北部为气旋式环流，同时在吕宋海峡口存在从南海至太平洋的水体交换；（3）将该流场信息与HYCOM和YoMaHa'07两种资料对比，吻合度较高，与HYCOM再分析资料的偏差分布趋近于正态分布，海流的东西向分量的均方根误差为3.28 cm/s，南北向分量的均方根误差为3.26 cm/s。总体而言，利用Argo轨迹资料能够有效地反演出南海地区海盆尺度的中层环流特征。     

基于海图数据的水下岸坡插值精度分析对比研究

数字高程模型是研究水下岸坡冲淤变化的一种重要手段。不同的插值方法和像元大小都会对数字高程模型的精度产生影响,从而导致冲淤分析结果的变化。本研究使用了六种常用的插值方法 (ANUDEM、反距离函数法、克里金法、自然邻域法、样条函数法、不规则三角网转栅格法)对莱州湾和烟台港不同年份和尺度的水深数据进行了插值,计算了均方根预测误差、源数据残差均方根误差、残差均值、残差最大值和残差最小值等精度计算指标。结果表明ANUDEM和自然邻域法的均方根预测误差和源数据残差均方根误差均小于1 m。ANUDEM和自然邻域法对不同尺度的水下岸坡数据插值有着较好的适用性。     

基于距平分析的Argo海表温度场重构

提出基于距平分析的Argo海表温度场(SST)重构方法,即在Argo浮标观测点提取温度距平值序列进行Kriging插值生成距平场,并叠加气候态SST的方法重构Argo海温场。以Argo数据相对稀少的2003年8月份和Argo数据相对较多的2012年8月份印度洋海域(60°S—30°N,25°—125oE)为例,重构水平分辨率为1°×1°的海表温度场。分析表明:(1)这种基于距平分析方法重构的海温场与对Argo数据直接Kriging插值获得的结果相比在精度上有大幅提高;(2)重构的温度场与最优插值海表温度场(OISSTV 2.0)的等温线具有高度的一致性,并且在Argo浮标附近海域有更好的细节表现;(3)即使在Argo数据相对稀少的海域,基于距平分析方法重构的海温场也能保持较高的精度要求,包括边缘海域和南大洋极锋附近均有较好表现。     

最优插值法在东海赤潮高发区赤潮生消过程数值模拟中的应用

将最优插值法与赤潮数值模型相结合,针对时空分辨率不统一的卫星遥感数据及海洋常规调查数据,进行了东海赤潮高发区海表温度场及海表营养盐浓度场的数据同化研究,并在此基础上进行了该海区春季赤潮过程的数值模拟研究。数据同化结果显示,最优插值数据同化方法不仅在一定程度上修正了海表温度场模拟结果的误差,尤其体现在对赤潮藻的生长影响较大的温度区段18—20℃等值线的南移,而且较为明显地优化了研究海域海表营养盐浓度场,使模拟结果更加接近观测值。对比赤潮过程数值模拟结果发现,在未加同化情况下,海区赤潮藻并未形成大规模赤潮,并且消散较快;而在加入同化后,研究海域交替出现了硅藻及甲藻的大范围赤潮,赤潮生消过程与现场调查数据分析结果较为一致。耦合了最优插值数据同化方法的赤潮数值模型,由于具有改进海洋环境背景场的优势,因此可以在赤潮预报预警工作中得到较好应用。     

Adjustment time of the first baroclinic Rossby wave in the global oceans

1Introduction Planetary waves involve the main processes bywhich perturbation signal in one part of the ocean istransferred to another part.In the1970s,mostof theprevious theoretical studies focus on the local Ekmanpumping and the nondispersive long baroc…     

南海罗斯贝变形半径的地理及季节变化

根据南海 1°× 1°网格的标准层季节平均温、盐度资料 ,在未引入Boussinesq近似条件下 ,采用改进的Thompson Haskell算法求解线性化斜压海洋水平大尺度波的垂直结构方程 (重力内波方程 ) ,从而得到了南海各网格点的第一斜压重力波相速度和相应的罗斯贝变形半径 ,并探讨其地理分布和季节变化特征 ,以期有助于南海环流和中尺度涡旋以及有关海洋侧边界效应的研究。     

Meso-scale available gravitational potential energy in the world oceans

1 IntroductionThe oceanic general circulation takes place inthe environments of gravity. As a mechanical sys-tem, the oceanic circulation requires sources of me-chanical energy to overcome friction and dissipation.Although the ocean receives a huge amount…     

北太平洋副热带逆流区涡旋动能谱的季节性变化及其机制

本文利用了23年的卫星高度计数据和WOA13气候态月平均温盐资料,考察了北太平洋副热带逆流(STCC)区涡旋动能谱及其涡旋尺度季节变化的动力过程。为了揭示其动力机制,本文采用了斜压2.5层模式并结合动能串级的理论进行分析。结果表明,在STCC区由于海洋层结及地转流的垂向剪切发生了季节性变化,从而产生的斜压不稳定是导致涡旋动能谱季节变化的原因。涡旋动能最大的时间发生在5—6月份,滞后于斜压最不稳定发生的时间(3月份)约2—3个月左右,这是由于斜压不稳定产生的扰动需要一定时间才能发展成振幅足够大的涡旋。斜压不稳定提供的能量使得涡旋相互作用加强,产生了动能逆向串级,动能谱向更大尺度转移。涡旋能量尺度在3月份仅为280km,而在9月份达到最高值335km左右。另一方面,我们发现STCC区动能谱斜率及动能谱通量也有季节变化,在涡旋动能最大的5—6月份,当尺度小于罗斯贝变形尺度时,谱斜率达到1k–3,而动能谱通量达到最大值。对STCC区涡动能谱及涡旋尺度季节变化的研究,对深入认识中尺度涡旋的产生及其演变机制有着重要的意义。     

Spatial scales of mesoscale eddies from GOCI Chlorophyll-a concentration images in the East/Japan Sea

The spatial scales of mesoscale eddies are of importance to understand physio-biogeochemical processes in the East/Japan Sea. Chlorophyll-a concentration images from the Geostationary Ocean Color Imager (GOCI) revealed numerous eddies during the phytoplankton bloom in spring. These eddies were manually digitized to obtain geolocation information at the peripheries from GOCI images and then least-square fitted to each ellipse. The elliptic elements were the geolocation position of the eddy center, the rotation angle from due east, the eccentricity, the lengths of the semi-major and semi-minor axes, and the mean radius of the ellipse. The spatial scales of eddies had a mean radii ranging from 10 km to 75 km and tended to be smaller in the northern region. The scales revealed a linear trend of about ?7.26 km/°N as a function of the latitude. This tendency depended on the latitudinal variation of the internal Rossby radius of deformation, which originates from the substantial difference in the density structure of the water column. The scales from the sea surface temperature image were larger by 1.30 times compared to those from ocean color image. This implies that physical processes along the periphery of the eddy affect the nutrient dynamics.     

Structure of a pair of anticyclonic vortices in northern part of the South China Sea in autumn of 1994

A pair of remarkable meso-scale anticyclonic vortices, one formed closely to another, inthe northern part of the South China Sea during the period from the later August to early September of 1994 were documented by the in situ observation data. Their spatial structures were examined in detail from the horizontal and two nearly perpendicular/vertical angles of view. It was shown that the horizontal scales of these two vortices were around 100, 50 km, and their vertical scales were about 500, 1000 m, respectively. Two "warm core" structures associated with these two vortices were found in their horizontal and vertical analyses. The closer spacing of these two vortices (namely, 60 km), which was smaller than the Rossby radius of deformation, suggested that they might merge with each other during their next evolution stages and form into a larger vortex eventually.     

Dominant spatial variability scales from observations around the Hawaiian Islands

We utilize a variety of available observations with a semivariogram technique to quantify the oceanic variability around the Hawaiian Islands. The Hawaiian Islands have a significant impact on the North Pacific circulation, and quantifying the characteristics of the variability is important for understanding the eddy energy, as well as required for statistical techniques to work with the data, such as optimal interpolation, data assimilation, etc. Both satellite sea surface height and temperature data are used to determine horizontal scales of variability, while Argo profiles, ship-borne profiles, and autonomous Seagliders provide estimates of the vertical scales. In the lee of the islands, satellite data reveal an increase in horizontal variability attributed to enhanced eddy activity that persists for over 1000 km westward; however, only within 400 km of the immediate lee the horizontal length scales are greatly reduced. Further west, length scales increase significantly indicating a change in the generation mechanism for eddy variability and where eddies merge and coalesce. The meridional length scale gradient is found to be larger than previous results and more representative of the gradient of the first baroclinic mode of the internal Rossby radius. Vertical length scales are shown to increase in the lee, with vertical temperature variability doubled from the windward side.     

副热带一热带太平洋密跃层水量交换年际变化的模拟研究

利用一个全球海洋环流模式在3组风应力资料的强迫下模拟分析了副热带太平洋向热带太平洋密跃层水量输送的年际变化特征及其和风应力的关系,并设计数值试验,研究了密跃层水量输送的变化机制.结果表明,副热带太平洋向赤道太平洋的密跃层水量输送具有显著的年际变化.在年际时间尺度上,南北太平洋西边界密跃层水量输送都起着补偿内部路径输送的...     

Diffraction of a long Kelvin wave at the apex angle formed by intersecting shores

This paper discusses the diffraction of a low-frequency Kelvin wave (having a frequency comparable to that of a baroclinic Rossby wave) at the apex angle. The problem is handled, with the Coriolis parameter being variable, by expanding into series over the minor parameter ε characteristic of the ratio between the deformation radius and the length of an incident wave travelling along a latitudinal shore. An analytical expression has been derived for a wave translating along meridional shore. It is demonstrated that when the latitudinal shore is located above the critical latitude, the energy flux through the horizontal cross-section transported by the wave coincides with the corresponding flux in the incident wave. If, on the other hand, it is situated below the critical latitude, then part of the energy is consumed by offshore Rossby waves. Translated by Vladimir A. Puchkin.     

The effect of large-scale bottom irregularities on the dynamics of Rossby waves in the ocean

This paper discusses, in terms of the geometrical optics approximation, how large-scale bottom irregularities influence the propagation of Rossby waves in the ocean. To describe the major peculiarities of the phenomenon, a two-layer model is applied, with the depth of the upper layer being considerably smaller than that of the lower layer. However, even with the bottom topography being allowed for, the wave motion is described by two Rossby wave modes, namely, a barotropic mode and a baroclinic mode. It is demonstrated that barotropic mode transformation caused by large irregularities of the sea-floor may lead to wave interaction, resulting in their anomalous distribution. Translated by Vladimir A. Puchkin.