利用卫星测高数据监测巢湖水位变化

针对传统的通过水位站点连续观测获取水位信息的方式需要耗费人力、物力和财力的问题,该文提出利用Cryosat-2测高数据对内陆湖泊湖面高变化进行监测,并研究了巢湖水位变化与气候的关系,得出巢湖湖面高季节性变化的规律;同时,与地面水位站实测水位数据进行比较,发现二者存在显著的线性相关性。结果表明,利用Cryosat-2测高数据对内陆湖泊湖面高变化进行监测具有一定的可行性。     

On the predictability of mode-1 internal tides

A frequency-wavenumber tidal analysis for deriving internal-tide harmonic constants from TOPEX/Poseidon (T/P) measurements of sea-surface height (SSH) has been developed, taking advantage of the evident temporal and spatial coherence and the weak dissipation of internal tides. Previous analyses consisted of simple tidal analysis at individual points, which gave inconsistent harmonic constants at altimeter track crossover points. Such analyses have difficulty in distinguishing between the effects of interference, incoherence, and dissipation. The frequency-wavenumber analysis provides an objective way to interpolate the internal tides measured along altimetry tracks to any arbitrary point, while leveraging all available data for optimal tidal estimates. Tidal analysis of T/P data from 2000 to 2007 is used to predict in situ time series measured during the 2001-2002 Hawaiian Ocean mixing experiment (HOME), the 1987 reciprocal tomography experiment (RTE87), and the 1991 acoustic mid-ocean dynamics experiment (AMODE), demonstrating both the temporal coherence and the lack of incoherent elements to this wave propagation. It has been conjectured that significant energy would be lost from mode-1 internal tides as they cross the 28.9°N critical latitude of parametric subharmonic instability (PSI). No apparent change in amplitude at 28.9°N was detected by this analysis, however. Further, after correcting for changes in background stratification, the amplitude of the mode-1 internal tide was found to decrease by less than 20% over the 2000 km between the Hawaiian Ridge and 40°N. A significant fraction of the variability of internal waves, that component associated with mode-1 internal tides, appears to be predictable over most of the world's oceans, using harmonic constants derived from satellite altimetry.     

中国近海海面高度异常资料再处理

卫星海面高度异常产品再处理的研究多集中在欧洲和美国近海,中国近海尚未有过。在产生AVISO(Archiving Validation and Interpolation of Satellite Oceanographic Data)全球0.25°多颗卫星海面高度异常产品时,只用了1/3~1/2的部分沿轨资料,给区域海洋动力学研究造成了一定的限制。本研究尝试利用多颗卫星的所有沿轨资料及25个测潮站的观测资料,通过最优插值方法产生一份新的中国近海海面高度异常资料。新资料的空间分辨率仍为0.25°,但使用了来自3颗卫星(Jason-1、Jason-2、Cryo Sat-2)的所有沿轨资料及25个测潮站的观测资料。新资料的范围为10°S~50°N、90°~160°E。新资料与AVISO资料的对比分析表明新资料更接近沿轨海面高度异常观测,同时也更接近测潮站资料。与AVISO资料相比,新资料与沿轨海面高度异常观测的均方根误差降低了10.03%,与测潮站资料的均方根误差降低了9.6%。     

Analysis of systematic error influences on accuracy of airborne laser scanning altimetry

The error sources related to the laser rangefinder, GPS and INS are analyzed in details. Several coordinates systems used in airborne laser scanning are set up, and then the basic formula of system is given. This paper emphasizes on discussing the kinematic offset correction between GPS antenna phase center and laser fired point. And kinematic time delay influence on laser footprint position, the ranging errors, positioning errors, attitude errors and integration errors of the system are also explored. Finally, the result shows that the kinematic time delay can be neglected as compared with other error sources. The accuracy of the coordinates is not only influenced by the amplitude of the error, but also controlled by the operation parameters such as flight height, scanning angle amplitude and attitude magnitude of the platform.     

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。     

利用GRACE数据反演东海沉积物变化

GRACE卫星的成功发射为海底沉积物的监测提供了新的方法.利用2003-2014年间的GRACE RL05数据,采用同期的测高数据对海面高变化进行改正,使用水文模式数据和基于均一假设的尺度因子估计方法处理泄漏误差,反演了东海地区的沉积物变化情况,并对GIA效应进行了改正.结果表明：东海入海口处沉积物的平均变化速率为5.44±0.88 mm·a^-1,最大值出现在浙江沿海地区,变化速率为6~7 mm·a^-1;在空间分布上,呈现河口处沉积速率大,远离河口的大洋地区沉积速率小的特征.在时空分布上均与实测数据很好的吻合.沉积物变化时间序列的周年项振为6.8 cm,周年变化主要与东海泥沙扩散路径相关的海洋环流模式有关;半周年项和两周年项振幅分别为0.6 cm和0.7 cm,这两项变化主要与长江流域降水引起的土壤侵蚀变化有关.最后,分析讨论了本文沉积物监测方法推广到其他地区的适用性和局限性.

     

利用卫星资料研究中国南海海底地形

基于海洋重力异常与海深之间的密切关系,推导了利用FFT技术由重力异常计算海深的模型;利用该模型联合卫星测高数据和海洋重力资料反演了中国南海2.5'×2.5'海底地形;探讨了各种地球物理信息对于反演海底地形的影响。     

基于Cryosat和Jason1GM数据的垂线偏差计算与分析

针对不同时空分辨率测高数据对测高垂线偏差计算结果的影响,联合使用Jason1波形数据和Cryo-sat数据,在对波形重跟踪处理和海面时变效应消弱预处理后,采用Sandwell方法和加权最小二乘法计算了三个典型区域的垂线偏差分量。研究结果与EGM2008模型检核表明,低轨道倾角的Jason1大地测量任务数据能有效提取垂线偏差东西分量信息,联合高轨道倾角的Cryosat测高数据可以提升垂线偏差计算精度,而引入重力场模型作为参考场可以进一步改进垂线偏差计算结果。     

GNSS-R星载测高的动态性误差和信号平行误差研究

基于目前GNSS-R(global navigation satellite systems reflectometry)星载测高的几何路径延迟模型,分析了模型中存在的动态性误差和信号平行误差,给出了产生误差的原因以及了误差的解析表达式。为了获得误差的量级大小,首先采用部分UK-DMC(united kingdom disaster monitor constellation)星载数据进行实验,得到了动态性误差和信号平行误差的在实验中的大小;然后以CHAMP(challenging mini-satellite payload)和COSMIC (constellation observing system for meteorology, ionosphere and climate)低轨卫星作为接收机平台,进行了大量的仿真分析。综合实例和仿真分析的结果,得出这两项误差能够达到m级的结论,这是在测高中不能被忽略的。最后给出了如何用精密的发射机和接收机轨道信息来校正这两项误差的方法。