基于TOPEX/Poseidon资料的南海海面高度场的时空特征分析

采用经验正交函数(EOF)分解方法，对TOPEX／Poseidon卫星高度计在南海获得的1992年10月到1999年9月约7a的海面高度观测资料进行分析，从而获得南海海面高度距平场典型的空间分布型态及其对应的时间变化特征。结果表明，南海海面高度距平场在空间上主要表现为两种典型的分布结构：(1)由于冬、夏季风反转造成海盆尺度的涡旋结构，这种分布结构对南海海面高度距平场的方差贡献达27．46％；(2)NE—SW即吕宋—越南反相双涡结构，其方差贡献达20．37％。这两个模态都明显反映了季风的反转以及季风结构所造成的影响。同时，对各空间典型场所对应的时间系数序列进行了傅立叶谱分析，结果表明南海海面高度距平场存在多种时间尺度的变化。     

南海海面风、浪场时空变化特征及其关系分析

利用长时间序列的卫星观测数据,对南海海域的风、浪场时空分布及其相互关系进行了分析。结果显示,海面风距平场VEOF分解后得到的第一模态具有明显的季节变化,即季风特征,说明季风是影响整个南海风速的主要因素;第二模态具有较强的区域变化特征,是季风转换时期的距平场特征;第三模态反映的是海面风距平场受陆地地形影响所表现的分布特征。有效波高距平场EOF分解后得到的第一模态、第二模态与风距平场的前2个模态的空间分布较为相似,并且,风、浪距平场第一模态间的相关系数达0.76,均说明南海作为边缘海其波浪场与风场变化有很好的相关性。有效波高第三模态的分布与风场的第三模态相关性较弱,反映的是受海底地形影响所表现的分布特征。     

南海及邻近海域海面风场季节性变化的空间差异

使用QuikSCAT月平均数据研究南海及邻近海域海面风场季节性变化的空间差异。矢量经验正交函数分析方法的结果表明,受季风影响该海域海面风场以季节性变化为主,包括年循环和半年周期循环,并且季风对各区域的影响强度也有所不同。通过计算各网格点风速时间序列的方差及季节性循环所占的比例可以得知,纬向风和经向风方差的空间分布形式不同,最大值分别发生在长山山脉以南和以东海面;与经向风相比,纬向风年周期循环所占的比例从南到北空间变化很大,从80%下降到10%,而在东海南部海域则以半年周期变化为主。选取5个代表性区域进行比较,可见海面风年变化形式也具有明显的空间差异。     

南海海面散度场与涡度场的季节变化特征

本文使用ＣＯＡＤＳ海面风资料，逐月计算了南海的散度场和涡度场，发现其具有明显的季节变化。夏季的辐合区正是台风多发海域。冬半年南海东北部的正涡度区，是东北季风在海峡附近地形影响下形成的，并可能成为南海东北部冬季气旋式海洋环流维持的外强迫源。     

南海QuikSCAT海面风场变化特征分析

基于QuikSCAT海面风场产品,对海面风场资料进行了EOF分析和随机动态分析,以此分析南海海面风场的变化特征。研究发现:海面原始风场风速季节变化最为明显,其变化占总变化方差的59.1%,黑潮的季节变化通过海气相互作用对南海局地风场有较明显的影响;原始风场第三模态及异常风场第二模态时间变化函数与SOI和PDO弱相关,且异常风场第二模态时间变化函数谱分析结果主要呈现5年的周期变化,南海海面风场变化与年际振荡有关;南海大部分海区风速呈现增长的趋势,但增长速率较小;风速增大最快的区域是台湾海峡以南海域和北部湾,增长速度达到0.05 ms-1a-1。     

南海几种海面风应力资料的比较分析

利用卫星遥感（ERS1、ERS2）资料、综合海洋大气资料集（COADS）资料、Hellerman与Rosenstein客观分析资料，提取南海海面风应力因子进行比较分析，发现遥感资料与其他两种资料相比，具有分辨率高、量值合理的特点，建议在研究南海海面风应力气候学特征及季节变化规律，尤其是中、小尺度涡旋时采用遥感资料。     

北大西洋风场和海浪场特点分析

根据1950～1995年共46a的北大西洋气象船舶报资料,对按5°×5°网格统计的风、浪要素进行分析研究,阐明了北大西洋风、浪、涌的特点及其变化规律.该区是世界典型的季风气候区,季风时期的风向、风浪传播方向、涌浪传播方向基本一致,低纬地区常年盛行东北浪.冬季季风比夏季季风强盛,相应的平均波高、大浪大涌频率也较大.该海域与北印度洋同属季风气候区,但其特点正好相反.本文提供了较翔实的风场和浪场资料及变化规律.     

2008年东海海面WRF风场和QuikSCAT风场差异分析

为了分析海面风场资料的实用性,利用WRF (Weather Research and Forecasting Model)模拟了2008年东海海面风场,并比较了WRF模拟结果与QuikSCAT卫星散射计资料的差异.结果表明,两种资料均能反映东海海面风场的季节性变化特征,台风月风速偏差波动较大.分析四个台风个例发现,当台风较弱时,两种风场资料分布情况较一致;当台风较强时,两种资料均有不同程度的偏差,在近海区域,WRF模拟结果相比QuikSCAT资料更好地描述台风周围风场特征.     

南海北部海面高度的季节内变异及其传播特征 *

利用25年(1993—2017)的卫星高度计资料, 采用复经验正交函数(complex empirical orthogonal function, CEOF)方法, 分析南海北部海区海面高度季节内变异的时空分布及传播特征。标准差分析表明, 南海北部海面高度的季节内变异(intra-seasonal variability of sea level anomalies, SLA-ISV)在沿陆坡外侧区较强, 且SLA-ISV表现出明显的季节性变化, 冬半年强于夏半年。CEOF前两个主要模态能较好地揭示研究海区SLA-ISV的时空分布及其传播特征, 并表明SLA-ISV的强度受到季节性变化和年际变化的调制。全年CEOF的第一模态揭示SLA-ISV从台湾岛西南至西沙群岛以东区域的冬半年西南向传播特征; 而全年CEOF的第二模态则表现了SLA-ISV分别在台湾岛西南和东沙群岛西南的西南向传播特征。南海北部中尺度涡季节变化统计分析表明, CEOF的分解结果与南海北部的涡旋活动一致。     

Trends of sea surface wind energy over the South China Sea

Studies on climate change typically consider temperature and precipitation over extended periods but less so the wind. We used the Cross-Calibrated Multi-Platform (CCMP) 24-year wind fi eld data set to investigate the trends of wind energy over the South China Sea during 1988-2011. The results reveal a clear trend of increase in wind power density for each of three base statistics (i.e., mean, 90 th percentile and 99 th percentile) in all seasons and for annual means. The trends of wind power density showed obvious temporal and spatial variations. The magnitude of the trends was greatest in winter, intermediate in spring, and smallest in summer and autumn. A greater trend of increase was found in the northern areas of the South China Sea than in southern parts. The magnitude of the annual and seasonal trends over the South China Sea was larger in extreme high events (i.e., 90 th and 99 th percentiles) compared to the mean conditions. Sea surface temperature showed a negative correlation with the variability of wind power density over the majority of the South China Sea in all seasons and annual means, except for winter (41.7%).     

基于EOF分析对南海西北海域水体光谱特性的研究

This study presents an analysis of the spectral characteristics of remote sensing reflectance(R_(rs)) in northwestern South China Sea based on the in situ optical and water quality data for August 2018.R_(rs)was initially divided into four classes,classes A to D,using the max-classification algorithm,and the spectral properties of whole R_(rs) were characterized using the empirical orthogonal function(EOF) analysis.Subsequently,the dominant factors in each EOF mode were determined.The results indicated that more than 95% of the variances of R_(rs) are partly driven by the back-scattering characteristics of the suspended matter.The initial two EOF modes were well correlated with the total suspended matter and back-scattering coefficient.Furthermore,the first EOF modes of the four classes of R_(rs)(A-D R_(rs)-EOF_1) significantly contributed to the total variances of each R_(rs) class.In addition,the correlation coefficients between the amplitude factors of class A-D R_(rs)-EOF_1 and the variances of the relevant water quality and optical parameters were better than those of the unclassified ones.The spectral shape of class AR_(rs)-EOF_1 was governed by the absorption characteristic of chlorophyll a and colored dissolved organic matter(CDOM).The spectral shape of class B R_(rs)-EOF_1 was governed by the absorption characteristic of CDOM since it exhibited a high correlation with the absorption coefficient of CDOM(a_g(λ)),whereas the spectral shape of class C R_(rs)-EOF_1 was governed by the back-scattering characteristics but not affected by the suspended matter.The spectral shape of class D R_(rs)-EOF_1 exhibited a relatively good correlation with all the water quality parameters,which played a significant role in deciding its spectral shape.     

Comparison among four kinds of data of sea surface wind stress in the South China Sea

By using remote sensing (ERS) data, FSU data, COADS data and Hellerman & Rosen-stein objective analysis data to analyze the sea surface wind stress in the South China Sea, it is found that the remote sensing data have higher resolution and more reasonable values. Therefore we suggest that remote sensing data be chosen in the study of climatological features of sea surface wind stress and its seasonal variability in the South China Sea, especially in the study of small and middle scale eddies.     

Bias correction of sea surface temperature retrospective fore-casts in the South China Sea

Offline bias correction of numerical marine forecast products is an effective post-processing means to improve forecast accuracy. Two offline bias correction methods for sea surface temperature(SST) forecasts have been developed in this study: a backpropagation neural network(BPNN) algorithm, and a hybrid algorithm of empirical orthogonal function(EOF) analysis and BPNN(named EOF-BPNN). The performances of these two methods are validated using bias correction experiments implemented in the South...     

大气低层风场对南海海温的影响及其与季风的关系

利用1960-1999年月平均海表温度资料和大气低层风场资料,分析了南海海表温度与局地风场之间的关系及其季节变化特征,讨论了局地风场对南海海温的影响与季风的联系.结果表明,南海海表温度异常与局地风场异常之间的关系具有明显的季节变化特征,南海海表温度异常在夏季与纬向风异常呈明显的负相关,在冬季与经向风异常呈明显的正相关,这种季节变化与东亚季风特性(即盛行风存在明显的季节变化)密切相关.为南海海表温度监测预测提供气候背景,从而也解释了过去在大气低层风速与南海海表温度异常相关性方面不同研究结果存在差异的原因.     

基于南海定点观测数据的强风场特性研究

为了满足我国海洋工程抗风设计需求,在南海某海洋平台定点开展了原型测量工作。通过对海面上82 m和29 m两处开展实测工作,获得了冬季寒潮和超强台风"尤特"影响下的风场现场实测数据。利用非平稳过程分析方法对两类强风过程的脉动风分量、湍流强度、阵风因子、湍流积分尺度和脉动风谱等风场特性进行了分析。验证了脉动风分布的高斯性,给出了湍流强度与阵风因子的非线性拟合参数,分析了不同高度处风场特性剖面变化规律,证明了脉动风实测谱与Von Karman经验谱的良好拟合关系。     

Rapid environmental assessment in the South China Sea: Improved inversion of sound speed profile using remote sensing data

Complex perturbations in the profile and the sparsity of samples often limit the validity of rapid environmental assessment (REA) in the South China Sea (SCS). In this paper, the remote sensing data were used to estimate sound speed profile (SSP) with the self-organizing map (SOM) method in the SCS. First, the consistency of the empirical orthogonal functions was examined by using k-means clustering. The clustering results indicated that SSPs in the SCS have a similar perturbation nature, which means the inverted grid could be expanded to the entire SCS to deal with the problem of sparsity of the samples without statistical improbability. Second, a machine learning method was proposed that took advantage of the topological structure of SOM to significantly improve their accuracy. Validation revealed promising results, with a mean reconstruction error of 1.26 m/s, which is 1.16 m/s smaller than the traditional single empirical orthogonal function regression (sEOF-r) method. By violating the constraints of linear inversion, the topological structure of the SOM method showed a smaller error and better robustness in the SSP estimation. The improvements to enhance the accuracy and robustness of REA in the SCS were offered. These results suggested a potential utilization of REA in the SCS based on satellite data and provided a new approach for SSP estimation derived from sea surface data.     

基于HY-2 卫星观测分析南海风浪关系

海面有效波高(H1/3)是表征海浪的重要参数,随着卫星遥感技术的发展,雷达高度计已成为获取海面有效波高的重要手段,但也只能对卫星星下点轨迹处进行有效观测,远无法满足大范围应用的需求.本研究结合2013年10月HY-2雷达高度计观测的海面有效波高和微波散射计观测的海面风场资料,分别对高、低风速下风浪数据进行拟合,建立了适用于0~40 m/s风速范围内的南海海域风浪关系模型,经模型比对和结果验证,结果表明,基于HY-2卫星数据分析建立的南海海域风浪关系模型是可信的,特别是低风速的风浪模型与实测数据建立的风浪模型具有很好的一致性;根据建立的风浪关系模型,从卫星散射计大面观测的海面风场出发,能推算出风浪条件下海面有效波高的大面信息,数据覆盖远高于卫星高度计的星下点观测,能为分析和预报海浪、风暴潮灾害提供大范围的海面有效波高信息.     

南海表层水温年际变化的大尺度特征

通过对COADS海洋气象资料的分析,得出南海表层水温(SST)年际变化的若干大尺度特征.结果表明:南海SST年际具有一定的准周期性,其显著周期为24～30个月;南海SST年际变化与年循环之间有着一种锁相关系,关键位相在于北半球冬春季节;南海典型冷暖年份合成SST距平场的时空结构十分相似;在年际时间尺度上,南海SST和南方涛动指数有反相关系,与经向风海面热收支之间有同位相关系;南海暖池面积指数的年际变化与南海SST年际变化一致.