近岸海域EnviSat卫星测高波形重定的Threshold优化算法   总被引：4，自引：2，他引：2       下载免费PDF全文

郭金运  高永刚  常晓涛  黄金维 《地球物理学报》2010,53(4):807-814

波形重定是改善近岸海域卫星测高数据精度的一种有效方法.分析了EnviSat雷达测高波形重定算法,并对Threshold算法进行了优化,开发了波形重定程序;以地中海为实验区,利用几种波形重定方法,对近岸海域的EnviSat测高波形进行重定,认为优化的Threshold算法是几种波形重定算法中最稳健的重定算法,适合于地中海近岸海域EnviSat测高波形的重定,对其他近岸海域的应用也有一定的参考意义.  相似文献   

基于卫星测高交叉点的海洋表面地转流速度   总被引：3，自引：1，他引：2       下载免费PDF全文

郭金运  常晓涛  黄金维  孙佳龙  韩延本 《地球物理学报》2010,53(11):2582-2589

在流体静力平衡状态下,海洋Coriolis力和压力梯度平衡就形成地转流,世界上大多数海流都近似为地转流.本文利用卫星测高交叉点方法计算海洋表面地转流速度,分析了利用测高交叉点计算地转流速度的不确定性,上升和下降弧段的海面倾斜在分辨率50 km上可以达到10^-7量级,才可能获得优于10 cm/s的地转流速度.在低纬度或者纬度接近卫星轨道倾角的地区,由交叉点方法计算的地转流速度精度低于中纬度地区.以中国台湾东部黑潮为试验区,利用最新的中国台湾周边海域大地水准面模型参考场计算高精度的大地水准面高,利用TOPEX/Poseidon和Jason-1的GDR数据(2002~2005年)计算海面高,然后计算交叉点的动力高,确定交叉点的地转流速度,结果与中国台湾NCOR(National Center for Ocean Research)的流速基本一致.  相似文献   

Tide model comparison over the Southwestern Atlantic Shelf     

Martin Saraceno  E.E. D’Onofrio  M.E. Fiore  W.H. Grismeyer 《Continental Shelf Research》2010

Sea surface height (SSH) as measured by satellites has become a powerful tool for oceanographic and climate related studies. Whereas in the open ocean good accuracy has been achieved, more energetic dynamics and a number of calibration problems have limited applications over continental shelves and near the coast. Tidal ranges in the Southwestern Atlantic (SWA) continental shelf are among the highest in the world ocean, reaching up to 12 m at specific locations. This fact highlights the relevance of the accuracy of the tidal correction that must be applied to the satellite data to be useful in the region. In this work, amplitudes and phases of tidal constituents are extracted from five global tide models and three regional models and compared to the corresponding harmonics estimated from coastal tide gauges (TGs) and satellite altimetry data. The Root Sum Square (RSS) of the misfit of the common set of the five tidal constituents solved by the models (M₂, N₂, S₂, K₁ and O₁) is higher than 18 cm close to the coast for two of the regional models and higher than 24.5 cm for the rest of the models considered. Both values are too high to provide an accurate estimation of geostrophic non-tidal currents from satellite altimetry in the coastal region. On the other hand, the global model with the highest spatial resolution has a RSS lower than 4.5 cm over the continental shelf even when the non-linear M₄ overtide is considered. Comparison with in-situ current measurements suggests that this model can be used to de-tide altimetry data to compute large-scale patterns of SSH and associated geostrophic velocities. It is suggested that a local tide model with very high resolution that assimilates in-situ and satellite data should meet the precision needed to estimate geostrophic velocities at a higher resolution both close to the coast and over the Patagonian shelf.  相似文献   

Using satellite altimetry data to augment flow estimation techniques on the Mekong River   总被引：2，自引：0，他引：2  

S. J. Birkinshaw  G. M. O'Donnell  P. Moore  C. G. Kilsby  H. J. Fowler  P. A. M. Berry 《水文研究》2010,24(26):3811-3825

Satellite altimetry is routinely used to provide levels for oceans or large inland water bodies from space. By utilizing retracking schemes specially designed for inland waters, meaningful river stages can also be recovered when standard techniques fail. Utilizing retracked waveforms from ERS‐2 and ENVISAT along the Mekong, comparisons against observed stage measurements show that the altimetric measurements have a root mean square error (RMSE) of 0·44–0·65 m for ENVISAT and 0·46–0·76 m for ERS‐2. For many applications, however, stage is insufficient because discharge is the primary requirement. Investigations were therefore undertaken to estimate discharges at a downstream site (Nakhon Phanom (NP)) assuming that in situ data are available at a site 400 km upstream (Vientiane). Two hypothetical, but realistic scenarios were considered. Firstly, that NP was the site of a de‐commissioned gauge and secondly, that the site has never been gauged. Using both scenarios, predictions were made for the daily discharge using methods with and without altimetric stage data. In the first scenario using a linear regression approach the altimetry data improved the Nash‐Sutcliffe r² value from 0·884 to 0·935. The second scenario used known river cross‐sections while lateral inflows were inferred from a hydrological model: this scenario gave an increase in the r² value from 0·823 to 0·893. The use of altimetric stage data is shown to improve estimated discharges and further applications are discussed. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

A unified global height reference system as a basis for IGGOS   总被引：1，自引：0，他引：1  

Johannes Ihde  Laura Snchez 《Journal of Geodynamics》2005,40(4-5):400

The definition of a global height reference system is based on a mean sea surface, gravity field parameters, and a three-dimensional terrestrial reference frame (TRF). Tide gauge records, satellite altimetry, gravity measurements on Earth and from space, TRF coordinates, and spirit levelling have to be combined for the realization of the vertical reference frame. Observations and parameters have to be consistent with respect to the used standards, conventions and models. They have to provide globally unified reference surfaces (geoid or quasigeoid, respectively, and mean sea surface). The continental reference systems of Europe (EUREF, ECGN) and South America (SIRGAS) are considering these requirements in their strategies. They are presented here, and slightly different definitions and realizations for a globally unified height reference system are discussed.  相似文献   

Amazon River discharge estimated from TOPEX/Poseidon altimetry     

Elena A. Zakharova  Alexei V. Kouraev  Anny Cazenave  Frédérique Seyler 《Comptes Rendus Geoscience》2006,338(3):188-196

This paper presents an application of the TOPEX/Poseidon (T/P) satellite altimetry data to estimate river discharge at three sites along the Amazon River. We discuss the methodology to establish empirical relationships between satellite-derived water levels and daily estimations of river discharges based on rating curves and in situ level measurements at gauging stations. Three sites are chosen: Manacapuru (River Solimões), Jatuarana (nearby the confluence of the Solimões and Rio Negro rivers) and Óbidos (Amazon River). We then reconstruct the satellite-based river discharge over a 10-year time span (1992–2002). Comparison between satellite-derived and river discharge at the gauging stations shows that the T/P data can successfully be used for hydrological studies of large rivers, in providing in particular discharge estimates when in situ data are not available. To cite this article: E.A. Zakharova et al., C. R. Geoscience 338 (2006).  相似文献   

Determination of Geoid over South China Sea and Philippine Sea from Multi-satellite Altimetry Data     

Isaac Dadzie 《地球空间信息科学学报》2007,10(1):27-32

A new computational procedure for derivation of marine geoid on a 2.5′×2.5′grid in a non-tidal system over the South China Sea and the Philippine Sea from multi-satellite altimeter sea surface heights is discussed. Single-and dual-satellite crossovers were performed, and components of deflections of the vertical were determined at the crossover positions using Sand-well's computational theory, and gridded onto a 2.5′×2.5′resolution grid by employing the Shepard's interpolation procedure. 2.5′×2.5′grid of EGM96-derived components of deflections of the vertical and geoid heights were then used as reference global geopotential model quantities in a remove-restore procedure to implement the Molodensky-like formula via 1D-FFT technique to predict the geoid heights over the South China Sea and the Philippine Sea from the gridded altimeter-derived components of deflec-tions of the vertical. Statistical comparisons between the altimeter-and the EGM96- derived geoid heights showed that there was a root-mean-square agreement of ±0.35 m between them in a region of less tectonically active geological structures. However, over areas of tectonically active structures such as the Philippine trench, differences of about -19.9 m were obtained.  相似文献   

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褚永海  罗丹丹  傅露  倪清 《大地测量与地球动力学》2014,34(1):68-71

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渤海湾航空重力及其在海域大地水准面精化中的应用   总被引：1，自引：1，他引：0  

孙中苗  翟振和  肖云 《测绘学报》2014,43(11):1101-1108

近海航空重力数据在陆海大地水准面统一中起着重要作用。近3年来,利用我国首套航空重力测量系统(CHAGS)完成了渤海湾地区近20万平方千米的5′×5′格网平均重力异常数据的获取。本文首先介绍了渤海湾地区航空重力测量的概况,给出航空重力测量数据的处理要点;然后,详细讨论了航空重力测量的精度评估方法,其中针对该区域的测线布设特点,提出了"重叠格网比较法"以评估格网平均重力异常的内符合精度。结果表明,对于5′的波长分辨率,交叉点重力异常不符值在抗差后的中误差约为1.5 mGal,重叠格网法获得的5′×5′格网平均重力异常的中误差约为1.6 mGal;5′×5′格网重力异常与卫星测高和船测重力的比较精度优于3.0mGal;由航空重力测量获得的1°×1°格网平均重力异常与GOCE卫星重力位模型的计算值相比较,其系统性差异小于0.5 mGal、中误差约为2.7 mGal。利用航空重力数据后,渤海湾区域大地水准面与16个GPS水准点的比较精度由EGM2008模型的约23 cm提高到约12 cm。  相似文献   

Preliminary Assessment of SARAL/AltiKa Observations over the Ganges-Brahmaputra and Irrawaddy Rivers     

F. Frappart  F. Papa  V. Marieu  Y. Malbeteau  F. Jordy  S. Calmant 《Marine Geodesy》2015,38(3):568-580

Radar altimetry has demonstrated strong capabilities for the monitoring of water levels of lakes, rivers and wetlands over the last 20 years. The Indo-French SARAL/AltiKa mission, launched in February 2013, is the first satellite radar altimetry mission to carry onboard a Ka-band sensor. We propose here to evaluate the potential of this new instrument for land hydrology through comparisons with other altimetry-derived stages and discharges in the Ganges-Brahmaputra and Irrawaddy river basins using its first year of data. Due to the lack of concomitant in situ measurements for the current period, Jason-2 data, previously evaluated against in situ gauge records, were used as reference. Comparisons between Jason-2 and SARAL-derived water levels and discharges, and Jason-2 and Envisat (which flew the same orbit as SARAL from 2002 to 2010)-derived ones, was performed. Time-series of only one year of SARAL-derived water levels and discharges present better performances (lower RMSE and higher R, generally greater than 0.95) than the ones derived from Envisat when compared with Jason-2.  相似文献