Assessment of three numerical solution strategies for gravity field recovery from GOCE satellite gravity gradiometry implemented on a parallel platform   总被引：5，自引：2，他引：5  

R. Pail  G. Plank 《Journal of Geodesy》2002,76(8):462-474

 The recovery of a full set of gravity field parameters from satellite gravity gradiometry (SGG) is a huge numerical and computational task. In practice, parallel computing has to be applied to estimate the more than 90 000 harmonic coefficients parameterizing the Earth's gravity field up to a maximum spherical harmonic degree of 300. Three independent solution strategies (preconditioned conjugate gradient method, semi-analytic approach, and distributed non-approximative adjustment), which are based on different concepts, are assessed and compared both theoretically and on the basis of a realistic-as-possible numerical simulation regarding the accuracy of the results, as well as the computational effort. Special concern is given to the correct treatment of the coloured noise characteristics of the gradiometer. The numerical simulations show that the three methods deliver nearly identical results—even in the case of large data gaps in the observation time series. The newly proposed distributed non-approximative adjustment approach, which is the only one of the three methods that solves the inverse problem in a strict sense, also turns out to be a feasible method for practical applications. Received: 17 December 2001 / Accepted: 17 July 2002 Acknowledgments. We would like to thank Prof. W.-D. Schuh, Institute of Theoretical Geodesy, University of Bonn, for providing us with the serial version of the PCGMA algorithm, which forms the basis for the parallel PCGMA package developed at our institute. This study was partially performed in the course of the GOCE project `From E?tv?s to mGal+', funded by the European Space Agency (ESA) under contract No. 14287/00/NL/DC. Correspondence to: R. Pail  相似文献   

Quasi-conservative behaviour of Be in deep waters of the Weddell Sea and the Atlantic sector of the Antarctic Circumpolar Current     

M. Frank  M.M. Rutgers van der LoeffPeter W. Kubik  Augusto Mangini 《Earth and Planetary Science Letters》2002,201(1):171-186

We present the first transect of dissolved ¹⁰Be depth profiles across the Antarctic Circumpolar Current (ACC) in the Atlantic sector. North of the Polar Front the ¹⁰Be concentrations increase continuously from very low values at the surface to values of up to 1600 atoms/g at depth. Deep water ¹⁰Be concentrations of particular water masses are consistent with earlier results obtained further north. South of the Polar Front and in the Weddell Sea the distribution of ¹⁰Be is also characterised by low surface concentrations but below 1000 m depth the concentrations are relatively constant and significantly higher (up to 2000 atoms/g) than further north, probably as a result of mixing and advection of water masses of Pacific origin. Overall the deep water ¹⁰Be distribution is obviously not significantly affected by scavenging processes or ice melt and comparison with the density distribution suggests that ¹⁰Be can be viewed as a quasi-conservative tracer. This provides a tool for an improved understanding of the behaviour of other more particle reactive trace metals in the Southern Ocean such as ²³⁰Th: in deep waters north of the ACC/Weddell Gyre boundary (AWB) ¹⁰Be/²³⁰Th has a relatively constant value (1.7±0.3×10⁹ atoms/dpm) over a wide density range whereas south of the AWB the ratio is significantly lower (1.1±0.2×10⁹ atoms/dpm). This normalisation to ¹⁰Be corroborates that ²³⁰Th is enriched by 50% due to accumulation south of the AWB as a consequence of minimal particulate fluxes. The quasi-conservative behaviour deduced from our results also implies that ¹⁰Be can only be used as a tracer for Southern Ocean particle fluxes in the past if ocean circulation patterns and water mass residence times did not change significantly.  相似文献   

北冰洋-欧亚大陆-太平洋地学断面东南段岩石圈有效弹性厚度   总被引：4，自引：1，他引：4  

袁炳强  YveteH.PoudjomDjomani 《地球科学》2002,27(4):397-402

大陆岩石圈有效弹性厚度（Te）是表示岩石圈强度的参数，计算该参数对研究岩石圈大规模构造，分析大陆板块内的均衡补偿机制有一定意义。利用Forsyth提出的相关技术计算的北冰洋－欧亚大陆－太平洋地学断面东南段自黑水到泉州的Te值，并分析了重力和地形波长的相关性特征，初步认为：计算Te值所选的每个数据块在短波长（6.6-100km)内岩石圈板块的强度足以平衡地形负载，重力和地形不相关；在长波长（100－250km)内，地形及地下负载由弯曲模型补偿，岩石圈板块在地形及地下负载作用下而挠曲。断面通过地段具有较低热流密度值的陆核有较高的Te值，具有较高热流密度值的宁化，大田地区有较低的Te值，反映了较高的热流密度值对应较低的Te值，较低的热流密度值对应较高Te 值的关系，Te可分为南东低值段和北西高值段，地壳厚度大体上与Te值呈正相关关系。  相似文献   

北太平洋冬季阻塞性高压对船舶西行航线的影响*          下载免费PDF全文

尹尽勇杜秉玉  李泽椿齐桂英 《应用气象学报》2002,13(6):704-710

通过对近10年北太平洋冬季阻塞性高压的建立、维持及崩溃的天气形势分析，结合船舶气象导航的原理、气象航线的设计以及影响航线选择的因素，指出了有利于北太平洋冬季西行高纬度航线的阻塞高压形式，为船舶西行选择高纬度航线提供了气象理论依据。  相似文献   

The vertical scale of isopycnal intrusions: comment on a paper by Ruddick, Phillips and Turner     

Melvin E. Stern   《Dynamics of Atmospheres and Oceans》2002,35(3)

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Assimilation of SLA and SST data into an OGCM for the Indian Ocean   总被引：6，自引：0，他引：6  

Vibeke E. J. Haugen  Geir Evensen 《Ocean Dynamics》2002,52(3):133-151

 Remotely sensed observations of sea-level anomaly and sea-surface temperature have been assimilated into an implementation of the Miami Isopycnic Coordinate Ocean Model (MICOM) for the Indian Ocean using the Ensemble Kalman Filter (EnKF). The system has been applied in a hindcast validation experiment to examine the properties of the assimilation scheme when used with a full ocean general circulation model and real observations. This work is considered as a first step towards an operational ocean monitoring and forecasting system for the Indian Ocean. The assimilation of real data has demonstrated that the sequential EnKF can efficiently control the model evolution in time. The use of data assimilation requires a significant amount of additional processing and computational resources. However, we have tried to justify the cost of using a sophisticated assimilation scheme by demonstrating strong regional and temporal dependencies of the covariance statistics, which include highly anisotropic and flow-dependent correlation functions. In particular, we observed a marked difference between error statistics in the equatorial region and at off-equatorial latitudes. We have also demonstrated how the assimilation of SLA and SST improves the model fields with respect to real observations. Independent in situ temperature profiles have been used to examine the impact of assimilating the remotely sensed observations. These intercomparisons have shown that the model temperature and salinity fields better resemble in situ observations in the assimilation experiment than in a model free-run case. On the other hand, it is also expected that assimilation of in situ profiles is needed to properly control the deep ocean circulation. Received: 8 January 2002 / Accepted: 8 April 2002  相似文献   

厄尔尼诺现象的构造基础与激发因素   总被引：9，自引：1，他引：9       下载免费PDF全文

杨学祥 《地震工程学报》2002,24(4):367-370

北太平洋对北极的半封闭状态和南太平洋对南极的开放状态是厄尔尼诺事件发生的构造基础，它导致北太平洋海表热能的积累和周期性向南太平洋输送，强潮汐振荡和火山喷发是其激发因素。  相似文献   

INDIAN OCEAN DIPOLE AND ITS RELATIONSHIP WITH ENSO MODE     

穆明权  李崇银 《Acta Meteorologica Sinica》2002,(4)

Near 100-year observed data sets are analyzed, and the results show that the variation of seasurface temperature(SST)in the equatorial Indian Ocean has a feature as a dipole oscillation.Thesituation of the dipole oscillation mainly shows the positive phase pattern(higher SST in the westand lower SST in the east than normal)and the negative phase pattern(higher SST in the east andlower SST in the west).The amplitude of the positive phase is larger than that of the negativephase.The dipole is stronger in September—November and weaker in January—April than inother months.It principally shows obviously inter-annual(4—5 year period)and inter-decadalvariation(25—30 year period).Although the Indian Ocean dipole in the individual year seems tobe independent of ENSO in the equatorial Pacific Ocean,in general,the Indian Ocean dipole hasobviously negative correlation with the Pacific Ocean “dipole”(similar to the inverse phase ofENSO).The atmospheric zonal(Walker) circulation is fundamental for relating the two dipoles toeach other.  相似文献   

Multi-technique monitoring of ocean tide loading in northern France     

Muriel Llubes  Nicolas Florsch  Jean-Paul Boy  Martine Amalvict  Pascal Bonnefond  Marie-Noëlle Bouin  Stphane Durand  Marie-France Esnoult  Pierre Exertier  Jacques Hinderer  Marie-Franoise Lalancette  Frdric Masson  Laurent Morel  Joëlle Nicolas  Mathilde Vergnolle  Guy Wppelmann 《Comptes Rendus Geoscience》2008,340(6):379-389

We have organised afield study of ocean tide loading in the northwestern part of France, where tidal amplitudes are known to be among the highest in the world. GPS and gravimetric techniques have already proved their capability to measure such weak and high-frequency signals. In this study, these classical observations are complemented with less usual techniques, such as tiltmeter and Satellite Laser Ranging (SLR) measurements. We present here the preliminary results for a common period of observations spanning from 12–19 May 2004. Additional measurements from the French Transportable Laser Ranging Station (FTLRS) were available during September and October 2004. Observation residuals are computed as the difference between the observed and the predicted time signals. We obtain small RMS residuals for GPS measurements (2.5/3.1/4.5 mm for the eastward, northward and upward components), for absolute and relative gravimetry (9 nm/s² and 13 nm/s²) and for tiltmeters (0.05 μrad for EW component). We also fit the amplitude of the main M2 tidal constituent to FTLRS observations and we find a value of 3.731 cm, which is comparable to the theoretical value.  相似文献   

2006年北太平洋柔鱼作业渔场时空变化及其与表温的关系     

陆化杰  陈新军 《广东海洋大学学报》2008,28(1):93-97

<正>柔鱼(Ommastrephes bartramii)广泛分布在北太平洋,20世纪70年代初首先由日本鱿钓船开发,我国大陆于1993年开始利用该资源,1994年进行较大规模地商业性生产。目前北太平洋鱿钓渔业已成为我国远洋渔业的支柱[1]。据估计,历史上北太平洋柔  相似文献