基于神经网络的卫星高度计海面风速反演算法

通过对TOPEX/Poseidon高度计资料与NDBC浮标实测数据进行时空匹配处理,得到同步数据集,利用人工神经网络方法试验得到海面风速反演算法,并与业务运行的M CW算法进行分析比较,指出考虑波浪状态影响因素的神经网络算法在均方根误差和对称性方面的优越性。研究表明利用神经网络方法反演海面风速是可行的。     

星载雷达高度计反演海面风速进展

因为星载雷达高度计风速资料有沿轨分辨率高、精度高的特点,对其进行深入研究有重要意义.在中国海洋二号动力环境卫星刚刚升空之际,对星载雷达高度计反演海面风速围内外研究进展作一个综述.首先介绍星载雷达高度计风速反演的理论依据及存在困难;然后以风速反演进展历程为主线,分别针对后向散射系数、波浪状态、降雨、白沫等物理量引入地球物...     

基于漂流浮标的南大洋卫星高度计有效波高研究

随着技术的进步和数据处理方法的完善,经过修正的卫星高度计数据已获得普遍认可.但在南大洋缺少波浪现场数据,卫星高度计在极端恶劣气候条件下获得数据的准确度仍受到一定程度的质疑.中国于2020年第36次南极考察中,在南大洋布放了一套感应耦合漂流浮标,可提供可靠的南大洋现场波浪数据.本文利用该漂流浮标2020年1月27日至9月...     

南海灾害性波浪基本特征研究

本文基于1991-2016年全球卫星高度计融合数据对南海灾害性波浪基本特征进行了分析,根据灾害性波浪诱发天气类型不同,将其分为"台风浪"和"非台风浪"。依此主线,对两类波浪在南海不同海域的特征进行了研究,并提出了用于定量研究两类波浪强度关系的台风浪权重系数（W）,得到了两类波浪在南海相对强弱关系的分布规律,量化研究了南海灾害性波浪的特征。本文以卫星高度计波高数据为样本进行了极值分析,得到了南海重现期波浪要素整体分布规律,研究发现W值大小与广义极值曲线类型显著相关。     

再分析风场驱动下的南海波浪模拟误差

本文采用国际上广泛应用的3种再分析风场驱动WAVEWATCH III模型得到了南海波浪后报数据,并基于全球卫星高度计波高数据和我国沿海浮标实测数据对不同的风场计算结果进行了对比分析,分析表明3种风场的误差特征相差明显,其中ERA-40风场偏小,CFSR风场非常适合模拟常见天气的波浪过程,NCDC风场适合模拟大浪过程。论文重点以NCDC风场后报波浪数据分析了波浪模型模拟误差特点,发现在台风频发的的南海北部海域,再分析风场易低估大值波高,而在季风影响明显的南海南部海域,再分析风场易高估波高。浮标周边2°范围海域内的卫星高度计波高模拟误差趋势与浮标波高模拟误差趋势相似,浮标波高数据的统计特征值与"2度法"提取的卫星高度计数据统计特征值具有较高一致性。     

海浪成长状态对TOPEX/Poseidon高度计风速反演的影响

以墨西哥湾同步高度计、浮标资料为例,研究了海浪成长状态对高度计风速反演的影响。同步的高度计风速和浮标风速比较显示,在墨西哥湾地区,海浪成长状态对高度计风速反演有较大影响。在考虑海浪成长状态影响的条件下,利用谱模型反演高度计风速,取得了较好的效果。与目前TOPEX/Poseidon高度计风速反演业务化算法相比,在海浪未充分成长条件下,考虑海浪成长状态影响后,根据谱模型反演获得的风速与浮标风速之间的均方根误差减小了30%,平均误差减小了83%。在利用谱模型算法反演高度计风速时,谱模型中的波龄因子(表示海浪成长状态)可以根据高度计测得的有效波高和风速获得,因此该方法具有广泛的适用性。     

波浪骑士数据在高度计有效波高检验中的再处理

以2011年10～11月南海现场试验得到的9次波浪骑士测量数据,进行波浪骑士再处理与默认计算结果比对。比对结果表明两者平均误差为0.16m,均方根误差为0.32m,分析产生误差的原因在于波浪骑士默认计算有效波高时间段的中心与卫星过境时间不统一和未进行数据质量控制。研究表明在卫星高度计有效波高产品检验中,波浪骑士测量的有效波高需要进行再处理,以达到减少卫星高度计有效波高检验误差的目的。     

基于SVR和LSTM算法反演散射计下有效波高研究

有效波高反演对于海洋工程及海洋环境安全具有重要意义.我国海洋二号(HY-2A)卫星载有散射计和高度计等获取海洋要素的仪器.散射计可获取海洋风场数据但无法直接获取有效波高数据,高度计可获取海洋有效波高数据但覆盖区域狭小.本文将散射计与高度计各自优势结合,利用支持向量回归(SVR)和长短期记忆(LSTM)智能算法反演散射计...     

Retrieving wave period of the North Pacific with TOPEX altimeter

利用TOPEX高度计和NDBC浮标同步观测数据,对7种高度计海浪周期反演模型进行了系统的比较分析,从反演模式的精度、反演周期整体分布、周期-波高的联合分布等方面对反演模型做出了评价,并根据墨西哥湾和夏威夷海域反演结果对模型的区域适应性进行了验证,结合Hasselmann风浪充分成长关系分析了不同海浪成分下模型的反演效果.分析发现,Mackay等于2008年提出的算法(简称M08)相对于其他算法精度最高,且在不同海域和不同海浪成分下精度没有明显差异.利用M08算法反演了北太平洋海域的海浪平均周期分布,讨论其空间分布特征和季节变化特征如下:北太平洋海域的平均周期在墨西哥湾、西里伯斯海等沿岸地区较小,在西风带海域为较大,并存在明显的地形、纬度差异和季节性变化特征.     

TOPEX高度计数据反演北太平洋海浪周期

利用TOPEX高度计和NDBC浮标同步观测数据,对7种高度计海浪周期反演模型进行了系统的比较分析,从反演模式的精度、反演周期整体分布、周期-波高的联合分布等方面对反演模型做出了评价,并根据墨西哥湾和夏威夷海域反演结果对模型的区域适应性进行了验证,结合Hasselmann风浪充分成长关系分析了不同海浪成分下模型的反演效果。分析发现,Mackay等于2008年提出的算法(简称M08)相对于其他算法精度最高,且在不同海域和不同海浪成分下精度没有明显差异。利用M08算法反演了北太平洋海域的海浪平均周期分布,讨论其空间分布特征和季节变化特征如下:北太平洋海域的平均周期在墨西哥湾、西里伯斯海等沿岸地区较小,在西风带海域为较大,并存在明显的地形、纬度差异和季节性变化特征。     

Calibration/Validation of an Altimeter Wave Period Model and Application to TOPEX/Poseidon and Jason-1 Altimeters

The altimeter radar backscatter cross-section is known to be related to the ocean surface wave mean square slope statistics, linked to the mean surface acceleration variance according to the surface wave dispersion relationship. Since altimeter measurements also provide significant wave height estimates, the precedent reasoning was used to derive empirical altimeter wave period models by combining both significant wave height and radar backscatter cross-section measurements. This article follows such attempts to propose new algorithms to derive an altimeter mean wave period parameter using neural networks method. Two versions depending on the required inputs are presented. The first one makes use of Ku-band measurements only as done in previous studies, and the second one exploits the dual-frequency capability of modern altimeters to better account for local environmental conditions. Comparison with in situ measurements show high correlations which give confidence in the derived altimeter wave period parameter. It is further shown that improved mean wave characteristics can be obtained at global and local scales by using an objective interpolation scheme to handle relatively coarse altimeter sampling and that TOPEX/Poseidon and Jason-1 altimeters can be merged to provide altimeter mean wave period fields with a better resolution. Finally, altimeter mean wave period estimates are compared with the WaveWatch-III numerical wave model to illustrate their usefulness for wave models tuning and validation.     

Calibration/Validation of an Altimeter Wave Period Model and Application to TOPEX/Poseidon and Jason-1 Altimeters

The altimeter radar backscatter cross-section is known to be related to the ocean surface wave mean square slope statistics, linked to the mean surface acceleration variance according to the surface wave dispersion relationship. Since altimeter measurements also provide significant wave height estimates, the precedent reasoning was used to derive empirical altimeter wave period models by combining both significant wave height and radar backscatter cross-section measurements. This article follows such attempts to propose new algorithms to derive an altimeter mean wave period parameter using neural networks method. Two versions depending on the required inputs are presented. The first one makes use of Ku-band measurements only as done in previous studies, and the second one exploits the dual-frequency capability of modern altimeters to better account for local environmental conditions. Comparison with in situ measurements show high correlations which give confidence in the derived altimeter wave period parameter. It is further shown that improved mean wave characteristics can be obtained at global and local scales by using an objective interpolation scheme to handle relatively coarse altimeter sampling and that TOPEX/Poseidon and Jason-1 altimeters can be merged to provide altimeter mean wave period fields with a better resolution. Finally, altimeter mean wave period estimates are compared with the WaveWatch-III numerical wave model to illustrate their usefulness for wave models tuning and validation.     

Study on wave energy resource assessing method based on altimeter data——A case study in Northwest Pacific

波浪能是一种重要的海洋可再生能源,在开发波浪能之前需要对波浪能的时空分布状况进行可靠的评估。高度计可以提供比海浪模式更为准确的海浪现场观测结果,可以作为波浪能资源评估的一种新的手段。高度计数据的优势在于对海浪有效波高的观测具有较高的精度。为了发挥高度计数据的特点和优势,实现高度计数据在波浪能资源评估研究中的应用,本文建立了一种适合于高度计数据的局部海域波浪能资源的评估方法,主要包括数据的选择和处理;评价指标体系的建立;区域等级划分标准的建立。然后,以西北太平洋为例论述了该方法的具体应用。研究表明:本文建立的评估方法可以有效的评估研究海域波浪能资源的储量和时空分布状况,可为波能电站的建站选址和波能转换装置的设计和运行提供科学的参考依据。     

Case studies of ERS-1 altimeter data applicating in China Sea

1 IwrRODUcrIONAn initial field of wave height in a computing domain is needed fOr integration ofnumerical wave model. Because real time. observation ocean data are scarce, now most ofinitial fields of ocean wave is produced by either reckoning wind fields or preceding 24hour prediction results. It is possible to form an initiaI field of ocean wave along with the..increasing satellite data, ship report and buoy data. Some of research works have beendone abroad (Janssen et a1, l989; LionelI…     

A Spectral Approach for Determining Altimeter Wind Speed Model Functions

We propose a new analytical algorithm for the estimation of wind speeds from altimeter data using the mean square slope of the ocean surface, which is obtained by integration of a widely accepted wind-wave spectrum including the gravity-capillary wave range. It indicates that the normalized radar cross section depends not only on the wind speed but also on the wave age. The wave state effect on the altimeter radar return becomes remarkable with increasing wind speed and cannot be neglected at high wind speeds. A relationship between wave age and nondimensional wave height based on buoy observational data is applied to compute the wave age using the significant wave height of ocean waves, which could be simultaneously obtained from altimeter data. Comparison with actual data shows that this new algorithm produces more reliable wind speeds than do empirical algorithms. This revised version was published online in July 2006 with corrections to the Cover Date.     

时空窗口对HY-2有效波高产品检验影响模拟研究

时空窗口的选择是卫星高度计有效波高产品检验的主要影响因素。采用Monte Carlo(MC)数学模拟的方法 ,研究了时空窗口对HY-2高度计有效波高检验的影响,并采用现场浮标测量数据验证了MC模拟的可靠性。MC模拟结果表明,采用浮标测量数据对HY-2高度计有效波高检验时,必须分海况选取对应的最优空间窗口进行,并给出不同海况下的最优的时空窗口。对于高海况需采用小的空间窗口,在1 m,2 m,3 m,4 m有效波高的海况下,其理想的时空窗口为0 min,117 km,30 km,18 km和13 km。     

基于现场观测数据的HY-2A卫星有效波高校正研究

Significant wave height(SWH) can be computed from the returning waveform of radar altimeter, this parameter is only raw estimates if it does not calibrate. But accurate calibration is important for all applications, especially for climate studies. HY-2a altimeter has been operational since April 2012 and its products are available to the scientific community. In this work, SWH data from HY-2A altimeters are calibrated against in situ buoy data from the National Data Buoy Center(NDBC), Distinguished from previous calibration studies which generally regarded buoy data as "truth", the work of calibration for HY-2A altimeter wave data against in situ buoys was applied a more sophisticated statistical technique—the total least squares(TLS) method which can take into account errors in both variables. We present calibration results for HY-2A radar altimeter measurement of wave height against NDBC buoys. In addition, cross-calibration for HY-2A and Jason-2 wave data are talked over and the result is given.     

Winds and Waves in the Yellow and East China Seas: A Comparison of Spaceborne Altimeter Measurements and Model Results

Wind speed and wave height measured by satellite altimeters represent a good data source to the study of global and regional wind and wave conditions. In this paper, the TOPEX altimeter wind and wave measurements in the Yellow and East China Seas are analyzed. The results provide a glimpse on the statistical properties and the spatial distributions of the regional wind and wave conditions. These data are excellent for use in the validation and verification of numerical simulations on global and regional scales. The altimeter measurements are compared with model output of temporal statistics and spatial distributions. The results show that the model simulations are in good agreement with TOPEX measurements in terms of the local mean and standard deviation of the variables (wave height and wind speed). For the comparison of spatial distributions, the quality of agreement between numerical simulations and altimeter measurements varies significantly from cycle to cycle of altimeter passes. In many cases, trends in the spatial distributions of wave heights and wind speeds between simulations and measurements are opposite. The statistics of biases, rms differences, linear regression coefficients and correlation coefficients are presented. A rather large percentage (∼50%) of cases show poor agreement based on a combination of low correlation, large rms difference or bias, and poor regression coefficient. There are indications that wave age is a factor affecting the performance of wave modeling skills. Generally speaking, the error statistics in the wave field is correlated to the corresponding error statistics in the wind field under the condition of active wind-wave generation. The error statistics between the wave field and the wind field become less correlated for large wave ages. This revised version was published online in August 2006 with corrections to the Cover Date.