利用卫星测高与验潮站数据监测越南近海海平面变化

利用卫星测高和验潮站资料计算分析了越南近海海平面变化。结果表明,两种数据得到的海平面变化过程具有很好的同步性,其中,由测高数据计算得到的1993-2015年越南近海整体上升速率为3.18 mm/a,沿岸验潮站海平面上升速率为4.1 mm/a。在整个验潮站观测时段,越南沿海海平面呈上升趋势,平均上升速率为3.02 mm/a。越南近海海平面表现为较强的季节性特征,在红河和湄公河三角洲沿岸地区,极易受到风暴潮和洪水等季节性气候的影响。     

ENVISAT测高卫星沿轨大地水准面梯度的海洋垂线偏差法研究

研究了利用沿轨大地水准面梯度数据计算海洋垂线偏差的最小二乘法,首先对ENVISAT测高数据进行各项地球物理改正得到近似测高大地水准面,然后计算沿轨大地水准面的梯度,接着用最小二乘法计算格网垂线偏差东西分量和南北分量的平均值。最后,用该方法计算了南中国海区域及其邻近海域(4°N～25°N,104°E～120°E)的5′×5′垂线偏差南北分量和东西分量,其精度优于7″,并与EGM96模型计算的垂线偏差值进行了比较,证明了该方法的有效性。     

基于波形分类的近海卫星测高数据自适应重跟踪方法

对卫星测高波形数据分类的聚类分析方法进行了改进,给出了一个用于确定最佳聚类数的有效性指标。以台湾海峡的Topex/Poseidon测高数据为例,对近海测高波形进行了分类研究,并分析了各类波形的最优重跟踪方法,在此基础上提出了近海测高波形重跟踪的自适应方法。对多个周期测高数据进行重跟踪实验,结果表明,自适应方法优于其他重跟踪方法,显著提高了近海测高数据的质量。     

全球海潮模型研究进展

阐述潮汐分析方法和建模方法,归纳总结了FES,CSR,GOT,NAO,TPXO,EOT,DTU,HAMTIDE及OSU系列全球海潮模型的建立机构、使用数据及构建方法等。对比分析2010年后出现的几种新的海潮模型(FES2012,EOT11a,DTU10和HAMTIDE11a)在南大洋的M2振幅,发现模型间差异主要集中在浅水及极地地区,其中极地地区高精度卫星测高数据的缺少及海冰的季节性变化,是导致建模精度较差的主要原因。最后对海潮模型的发展方向提出一些建议。     

Spectral accuracy of Jgm3 from satellite crossover altimetry

A detailed accuracy assessment of the geopotential model Jgm3 is made based on independent single- and dual-satellite sea-height differences at crossovers from altimetry with Jgm3-based orbits. These differences, averaged over long time spans and in latitude bands, are converted to spectra (latitude-lumped coefficients) by least-squares estimation. The observed error spectra so obtained are then compared directly to error projections for them from the Jgm3 variance–covariance matrix. It is found from these comparisons that Jgm3 is generally well calibrated with respect to the crossover altimetry of and between Geosat, TOPEX/Poseidon (T/P), and Ers 1. Some significant discrepancies at a few lower orders (namely m=1 and 3) indicate a need for further improvement of Jgm3. A companion calibration (by order) of the geopotential model Jgm2 shows its variance–covariance matrix also to be generally well calibrated for the same single- and dual-satellite altimeter data sets (but based on Jgm2 orbits), except that the error projections for Geosat are too pessimistic. The analysis of the dual-satellite crossovers reveals possible relative coordinate system offsets (particularly for Geosat with respect to T/P) which have been discussed previously. The long-term detailed seasonally averaged Geosat sea level with respect to T/P (covering 1985–1996) should be useful in gauging the relative change in sea level between different parts of the ocean over the single 4-year gap between these missions (1988–1992). Received: 16 February 1998 / Accepted: 25 November 1998     

Trends of sea level variations in the South China Sea from merged altimetry data

In this study, more than 13 yr of merged altimetry sea level anomalies (SLA) data were used to analyze the trends of sea level variations in the South China Sea (SCS). The result shows that the mean sea level over the SCS has a rise rate of 11.3 mm/yr during 1993–2000 and a fall rate of 11.8 mm/yr during 2001–2005. The geographical distribution of the sea level variations over the SCS is asymmetric with a pronounced variation existing in the deep water. The trends of thermosteric sea level variations were also examined using Ishii data and MITgcm assimilation data. The result indicates that the thermal change of the upper layer of the SCS has a significant contribution to the sea level variations. Heat budget analysis suggests that heat advection may be a key factor influencing the thermal change. Apart from thermal contribution, the effect of water exchange on the sea level variations was also studied.     

基于主波峰的自适应波形重跟踪算法研究

构建基于主波峰的自适应波形重跟踪算法（AMWRT）。首先提取主波峰,然后对主波峰分别应用经典的重心偏移法（OCOG）及阈值法（threshold）进行波形重跟踪,并进行精度比较,得到最优的观测水位。将AMWRT、OCOG和threshold法应用于长江中游地区,结果表明：1）测高卫星观测的长时间水位序列与水文站实测数据趋势较为一致;2）AMWRT算法相较于OCOG法及threshold法表现良好,比其中表现最好的经典threshold_0.5法的精度提高了30%,其绝对平均误差（MAE）和均方根误差（RMSE）分别降低至0.55 m和0.72 m。     

Comparison of Satellite Altimetric Gravity and Global Geopotential Models with Shipborne Gravity in the Red Sea

The determination of high-resolution geoid for marine regions requires the integration of gravity data provided by different sources, e.g. global geopotential models, satellite altimetry, and shipborne gravimetric observations. Shipborne gravity data, acquired over a long time, comprises the short-wavelengths gravitation signal. This paper aims to produce a consistent gravity field over the Red Sea region to be used for geoid modelling. Both, the leave-one-out cross-validation and Kriging prediction techniques were chosen to ensure that the observed shipborne gravity data are consistent as well as free of gross-errors. A confidence level equivalent to 95.4% was decided to filter the observed shipborne data, while the cross-validation algorithm was repeatedly applied until the standard deviation of the residuals between the observed and estimated values are less than 1.5 mGal, which led to the elimination of about 17.7% of the shipborne gravity dataset. A comparison between the shipborne gravity data with DTU13 and SSv23.1 satellite altimetry-derived gravity models is done and reported. The corresponding results revealed that altimetry models almost have identical data content when compared one another, where the DTU13 gave better results with a mean and standard deviation of ?2.40 and 8.71 mGal, respectively. A statistical comparison has been made between different global geopotential models (GGMs) and shipborne gravity data. The Spectral Enhancement Method was applied to overcome the existing spectral gap between the GGMs and shipborne gravity data. EGM2008 manifested the best results with differences characterised with a mean of 1.35 mGal and a standard deviation of 11.11 mGal. Finally, the least-squares collocation (LSC) was implemented to combine the shipborne gravity data with DTU13 in order to create a unique and consistent gravity field over the Red Sea with no data voids. The combined data were independently tested using a total number of 95 randomly chosen shipborne gravity stations. The comparison between the extracted shipborne gravity data and DTU13 altimetry anomalies before and after applying the LSC revealed that a significant improvement is procurable from the combined dataset, in which the mean and standard deviation of the differences dropped from ?3.60 and 9.31 mGal to ?0.39 and 2.04 mGal, respectively.     

基于卫星高度计资料提取浙江近海的潮汐信息

利用Topex/Poseidon(T/P)、Jason-1和Jason-2卫星24a的原始轨道及6a的变轨轨道高度计资料,对浙江近海区域内进行潮汐调和分析,得到8个主要分潮(Q_1、O_1、P_1、K_1、N_2、M_2、S_2和K_2)的调和常数.比较卫星轨道交叉点处潮汐调和常数结果显示,8个分潮总体综合误差在原始轨道,变轨轨道及原始轨道与变轨轨道交叉点处的和方根RSS值分别为3.16、7.02、5.54cm;用卫星高度计资料及31个近岸验潮站得到的潮汐分布与21个验潮站资料结果进行比较,M_2、S_2、N_2、K_1和O_1主要分潮的多点向量均方根偏差分别为4.32、3.64、1.97、2.61、1.83 cm;本研究结果与前人数值模拟结果比较显示M2、S2分潮在对比点处的多点向量均方根偏差在11、8 cm左右,最后给出了浙江近岸及近海区域更为精确的5个主要分潮(M_2、S_2、N_2、K_1和O_1)的同潮图.