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。     

联合卫星测高和GNSS观测的天津沿海近25年相对海平面变化分析

针对现有验潮公开数据因时间范围及潮位沉降修正等影响,难以真实反映天津沿海相对海平面变化的问题,基于全球导航卫星系统（global navigation satellite system,GNSS）与验潮并置观测,设计了联合卫星测高和GNSS观测的天津沿海相对海平面变化分析方法。分析结果显示,1993—2018年期间,塘沽验潮站点的相对海平面上升速率约为13.45±0.45 mm/a;联合4个虚拟并置观测站,得到天津沿海不同区域的相对海平面上升速率在11.15～19.17 mm/a,平均上升速率15.09±0.45 mm/a。沿海地面沉降是天津相对海平面上升速率偏高的主要因素（贡献率大于70%）,受地面沉降非均匀空间分布的影响,海平面上升速率存在区域差异,塘沽验潮站难以代表整个天津沿海的相对海平面变化。     

利用多代卫星测高资料监测1993～2011年全球海平面变化

联合多代测高卫星T/P、Jason-1/2海面高数据和验潮站数据,确定了各卫星高度计的长期低频漂移,建立了统一的卫星测高海面高观测值,研究了1993～2011年间全球平均海平面的变化。结果表明,近18a全球平均海平面以3.12±0.4mm·a-1的速率上升,其中,海平面年际信号与ENSO事件表现出较强的相关性。     

北极新奥尔松地区海平面变化和陆地垂直运动分析

近百年来,全球正经历着以变暖为显著特征的变化,海水增温膨胀、陆地冰川和极地冰盖融化等因素导致全球海平面持续上升。北极新奥尔松地区现保存有典型的极地原始生态系统,客观准确地分析该地区的海平面变化,可以更好地为该地区自然生态环境监测和保护以及气候变化研究等提供基础。联合利用卫星高度计、验潮站和全球卫星导航系统(global navigation satellite system,GNSS)观测资料分析新奥尔松地区的海平面变化的线性趋势和季节性规律,通过同时段资料(1993-2018年)的分析显示,该地区地壳呈上升趋势,上升速率为(8.09±0.19)mm/a;验潮站相对海平面呈下降趋势,下降速率为(-7.31±0.36)mm/a;利用地壳运动修正后的绝对海平面上升速率为(0.78±0.41)mm/a,低于全球同期水平,与卫星高度计观测的绝对海平面变化结果具有很好的一致性,二者相差(0.23±0.46)mm/a。在进行区域海平面变化分析时,可利用GNSS修正验潮站相对海平面获得该区域的绝对海平面变化。利用修正后的海平面资料分析结果显示,新奥尔松地区海平面变化具有明显的季节性规律,每年10月-11月为季节高海平面期,3月-4月为季节低海平面期。通过海表面温度与海平面的相关性分析认为,随着海表面温度变化,海平面也发生相应的变化。     

基于验潮数据的南极海平面相对变化分析

基于夏威夷海平面研究中心提供的南极6个验潮站多年逐时潮位数据,本文首先利用迭代调和分析对初步观测数据进行补缺,并在此基础上计算月平均海平面,最后利用功率谱分析、最大熵谱分析、奇异谱分析等方法确定海平面的相对变化速率和振动周期。研究表明,南极海平面相对上升速率与全球其他区域基本一致(3mm/a-7mm/a),但是在个别测站(例如:Esperanza)的上升速度非常明显,达到厘米级。     

我国近海1992-2006年海平面变化的小波分析

用14年多的多颗测高卫星同化海面异常数据,分析我国近海海平面信号变化特征,结果显示年周期信号在我国海域海平面变化中占有主导地位。其次,半年周期信号在南海也有较强显示,而黄海和东海则表示为高频信号,半年起伏及高频信号的周期和振幅均不稳定。首次在南海和东海海域发现存在一周期为准540 d的信号,其物理机制尚不明确。用标准Morlet小波变换方法对上述周期信号进行了提取。验潮站数据也证实了该信号的存在。海面异常分析结果显示在1993~2007年期间,我国海平面平均升高速率:黄海为(4.01±0.49)mm/a,东海为(4.61±0.35)mm/a,南海为(3.68±0.41)mm/a。海平面上升趋势地理分布结果显示海平面变化具有很大的空间差异性。     

利用时变潮时差进行水位改正

针对目前实施时差法水位改正时使用的潮时差未考虑时变现象的影响以及利用潮时差确定水位观测时段选择混乱等问题，提出利用逐时滑动时段确定潮时差以进行水位改正的方法，分析了潮时差时变现象的原因及潮时差逐时滑动时段与逐日独立时段确定结果的差异，推导了时差法水位改正的误差公式。以某海域验潮站为例，进行了水位改正的数据实验，比较了逐时滑动时段与逐日独立时段确定的潮时差的水位改正效果。实验结果表明，利用逐时滑动确定的潮时差进行水位改正，在理论与精度方面均对目前使用的时差法有所完善与提高，尤其在潮差差异较大的海域，改进效果更加显著。     

联合GPS基准站和验潮站数据确定海平面绝对变化

采用中国地壳运动观测网络工程厦门基准站的GPS观测数据以及厦门验潮站的验潮数据,计算了厦门海域的海平面绝对变化速度,并就高程变化问题作了深入讨论,表明点位高程变化呈周期性,几期GPS连续观测受其影响不能得出实际的高程线性变化速率,指出了要监测验潮站的地壳垂直运动,最好采用多年连续的GPS观测数据。     

验潮站坐标时间序列特性分析

文中以298个验潮站作为研究对象,采用广义高斯-马尔科夫模型(GGM)、自回归滑动平均模型(ARMA)以及分形自回归聚合滑动平均模型(ARFIMA)三种模型,对验潮站坐标时间序列噪声模型特性及海平面变化趋势进行估计分析,并探讨了时间跨度对验潮站速度估计的影响. 实验结果表明:验潮站坐标时间序列主要呈现为ARFIMA(1,0)、ARFIMA(2,2)、ARMA (1,0) 噪声特性;验潮站速度估计结果表明64.77%的站点速度值所处区间为0～4 mm/a,平均海平面速度为1.25 mm/a,整体处于上升趋势. 随着时间跨度的增加,验潮站坐标序列速度不确定度逐渐由发散趋于收敛,大于110 a的时间跨度有助于获取稳健的验潮站速度估计值.      

利用验潮站观测数据校正测高平均海平面变化线性漂移

针对卫星测高数据确定平均海平面变化速度中可能存在的线性漂移问题,利用全球快速验潮站观测数据,在进行精细数据预处理中,为保证两种数据观测含相同时变海平面信号,改进了同步校正方法,解决了每个验潮站参考基准不同导致验潮站上两种数据海平面变化差值无法进行全球平均的问题,并以T/P卫星观测数据为例,确定了其平均海平面变化线性漂移,为获取真实海平面变化速度提供了保证。     

IGS Tide Gauge Benchmark Monitoring Pilot Project (TIGA): scientific benefits

The establishment of a long-term stable global reference frame is important for studying sea level records for, e.g., climate-related studies. GPS stations connected to the tide gauge benchmarks provide the necessary technique. However, the analysis of existing GPS solutions showed inconsistencies within the time series especially for the height component. To solve related issues, in 2001 the IGS Tide Gauge Benchmark Monitoring Pilot Project was established. The aim is the processing and re-processing of GPS data of stations at or near tide gauges in order to provide homogeneous and high-quality estimates of the vertical motion. A second objective is the establishment, maintenance and expansion of existing network of GPS stations at tide gauges. During the recent years six different analysis centers have processed overlapping GPS at tide gauge networks and are providing individual solutions allowing now to provide a combined solution. The ansatz for the combination is explained and quality measures are given. In addition, on the basis of the reconstruction of sea level anomalies, the benefit of using the combined TIGA solution is demonstrated.     

How do Unmodeled Systematic Mean Sea Level Variations Affect Long-term Sea Level Trend Estimates from Tide Gauge Data?

Although there are over 1,800 globally distributed tide gauge stations, only a few hundred of them are suitable for monitoring and analyzing global mean sea level (MSL) changes. This is because several tide gauge records span short periods of time and therefore their trend estimates are adversely affected by unmodeled systematic sea level changes such as seasonal, interannual, decadal variations. This limitation can be improved by using more elaborate models that account for systematic fluctuations in MSL for shorter time-series. In this study, analytic expressions were derived to analyze and quantify the epoch-by-epoch and lump-sum effects of these systematic changes to the local MSL trend estimates as a function of the time-series‘ lengths. The numerical results reveal that systematic MSL variations, particularly transient/episodic ones, if they are not properly modeled or omitted from the models, will bias the trend estimates for the tide gauge data series around the world by up to 0.6 mm/year for the 50-year time-series that are needed for more reliable inferences about global MSL. Random effects, which are not a factor in estimating MSL trends for the long-term (>50 years) time-series, need to be scrutinized together with the systematic errors for time-series shorter than 50 years.     

Rescue of the historical sea level record of Marseille (France) from 1885 to 1988 and its extension back to 1849–1851

This paper describes the historical sea level data that we have rescued from a tide gauge, especially devised originally for geodesy. This gauge was installed in Marseille in 1884 with the primary objective of defining the origin of the height system in France. Hourly values for 1885–1988 have been digitized from the original tidal charts. They are supplemented by hourly values from an older tide gauge record (1849–1851) that was rediscovered during a survey in 2009. Both recovered data sets have been critically edited for errors and their reliability assessed. The hourly values are thoroughly analysed for the first time after their original recording. A consistent high-frequency time series is reported, increasing notably the length of one of the few European sea level records in the Mediterranean Sea spanning more than one hundred years. Changes in sea levels are examined, and previous results revisited with the extended time series. The rate of relative sea level change for the period 1849–2012 is estimated to have been \(1.08\pm 0.04\)  mm/year at Marseille, a value that is slightly lower but in close agreement with the longest time series of Brest over the common period ( \(1.26\pm 0.04\)  mm/year). The data from a permanent global positioning system station installed on the roof of the solid tide gauge building suggests a remarkable stability of the ground ( \(-0.04\pm 0.25\)  mm/year) since 1998, confirming the choice made by our predecessor geodesists in the nineteenth century regarding this site selection.     

我国高精度GPS陆海垂直运动监测网的建立与精度分析

为了将验潮站得到的海平面变化信息与难潮站所在陆地垂直运动分离开来,获得海平面变化的绝对信息,在我国沿海５个难潮站建立了一个高精度的ＧＰＳ陆海垂直运动监测网,采用ＧＡＭＩＴ和Ｇｌｏｏｋ软件对数据进行处理,并顾及影响高程因素中由于方位不对称引起的大气延迟改进的Ｎｉｅｌｌ模型,我们最终得到ＧＰＳ监测网毫米级的高程精度。     

利用TOPEX/Poseidon卫星测高资料监测全球海平面变化

本文利用１９９３年１月至１９９９年５月的ＴＯＰＥＸ／Ｐｏｓｅｉｄｏｎ卫星测高数据计算了全球海平变化。海平面模型误差和不恰当的加权方法都会影响全球海平面序列的周年变化,潮汐模型误差对于季节性变化有明显的影响。利用两个高度计算的海平面变化存在周年变化存在明显的差异,利用ＴＯＰＥＸ高度计和Ｐｏｓｅｉｄｏｎ高度计得到的该时段全球平均海平面的变化率分别为２．０ｍｍ／ａ和－０．５ｍｍ／ａ。与南方涛动指数的比较     

Observation on height changes of chinese tide gauges by GPS

IntroductionBecause of global temperature rising and glacierthawing,the sea level has risen about 10-25 cmin the past century[1]. The sea level change isone of the main ai ms in global change monito-ring. Presently the basic tool used in sea levelmonitori…     

Observation on height changes of chinese tide gauges by GPS

The height changes of tide gauges directly influence sea level observation. For research of sea level variation in large region or globe, the land vertical displacement must be considered. Two sessions of GPS and absolute gravity observations in 2001 and 2003 are used to determine the horizontal and vertical motion of China coast in ITRF2000 and Eurasia frame. The difference between results of continuous observation and periodic observation is discussed.