A Reconstruction of Observed Profiles in the Sea East of Japan Using Vertical Coupled Temperature-Salinity EOF Modes   总被引：4，自引：0，他引：4  

Yosuke Fujii  Masafumi Kamachi 《Journal of Oceanography》2003,59(2):173-186

It is important to estimate hard-to-observe parameters in the ocean interior from easy-to-observe parameters. This study therefore demostrates a reconstruction of observed temperature and salinity profiles of the sea east of Japan (30°≈40°N, 140°≈150°E). The reconstruction was done by estimating suboptimal state from several values of the observed profiles and/or sea surface dynamic height (SDH) calculated from the profiles. The estimation used a variational method with vertical coupled temperature-salinity empirical orthogonal function (EOF) modes. Profiles of temperature and salinity in the subtropical region are effectively reconstructed from in situ temperature profile data, or sea surface temperature (SST) and SDH. For example, the analyzed temperature field from SST and SDH has an accuracy to within 1°C in the subtropical region. Salinity in the sea north of Kuroshio, however, is difficult to estimate because of its complex variability which is less correlated with temperature than in the subtropical region. Sea surface salinity is useful to estimate the subsurface structure. We also show the possibility that the estimation is improved by considering nonlinearity in the equation calculating SDH from temperature and salinity analysis values in order to examine the misfit between analysis and observation. Analysis using TOPEX/POSEIDON altimetry data instead of SDH was also performed. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

Preconditioned Optimizing Utility for Large-dimensional analyses (POpULar)     

Yosuke Fujii 《Journal of Oceanography》2005,61(1):167-181

I present the derivation of the Preconditioned Optimizing Utility for Large-dimensional analyses (POpULar), which is developed for adopting a non-diagonal background error covariance matrix in nonlinear variational analyses (i.e., analyses employing a non-quadratic cost function). POpULar is based on the idea of a linear preconditioned conjugate gradient method widely adopted in ocean data assimilation systems. POpULar uses the background error covariance matrix as a preconditioner without any decomposition of the matrix. This preconditioning accelerates the convergence. Moreover, the inverse of the matrix is not required. POpULar therefore allows us easily to handle the correlations among deviations of control variables (i.e., the variables which will be analyzed) from their background in nonlinear problems. In order to demonstrate the usefulness of POpULar, we illustrate two effects which are often neglected in studies of ocean data assimilation before. One is the effect of correlations among the deviations of control variables in an adjoint analysis. The other is the nonlinear effect of sea surface dynamic height calculation required when sea surface height observation is employed in a three-dimensional ocean analysis. As the results, these effects are not so small to neglect.  相似文献   

State Estimation of the North Pacific Ocean by a Four-Dimensional Variational Data Assimilation Experiment   总被引：1，自引：0，他引：1  

Toshiyuki Awaji  Shuhei Masuda  Yoichi Ishikawa  Nozomi Sugiura  Takahiro Toyoda  Tomohiro Nakamura 《Journal of Oceanography》2003,59(6):931-943

A four-dimensional variational data assimilation system has been applied to an experiment to describe the dynamic state of the North Pacific Ocean. A synthesis of available observational records and a sophisticated ocean general circulation model produces a dynamically consistent dataset, which, in contrast to the nudging approach, provides realistic features of the seasonally-varying ocean circulation with no artificial sources/sinks for temperature and salinity fields. This new dataset enables us to estimate heat and water mass transports in addition to the qualification of water mass formation and movement processes. A sensitivity experiment on our assimilation system reveals that the origin of the North Pacific Intermediate Water can be traced back to the Sea of Okhotsk and the Bering Sea in the subarctic region and to the subtropical Kuroshio region further south. These results demonstrate that our data assimilation system is a very powerful tool for the identification and characterization of ocean variabilities and for our understanding of the dynamic state of ocean circulation. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

Coupling a two-way nested primitive equation model and a statistical SST predictor of the Ligurian Sea via data assimilation     

A. Barth  A. Alvera-Azcrate  J.-M. Beckers  M. Rixen 《Ocean Modelling》2006,13(3-4):255-270

A primitive equation model and a statistical predictor are coupled by data assimilation in order to combine the strength of both approaches. In this work, the system of two-way nested models centred in the Ligurian Sea and the satellite-based ocean forecasting (SOFT) system predicting the sea surface temperature (SST) are used. The data assimilation scheme is a simplified reduced order Kalman filter based on a constant error space. The assimilation of predicted SST improves the forecast of the hydrodynamic model compared to the forecast obtained by assimilating past SST observations used by the statistical predictor. This study shows that the SST of the SOFT predictor can be used to correct atmospheric heat fluxes. Traditionally this is done by relaxing the model SST towards the climatological SST. Therefore, the assimilation of SOFT SST and climatological SST are also compared.  相似文献   

附加约束条件的序贯平差   总被引：1，自引：0，他引：1  

曾安敏  杨元喜  欧阳桂崇 《武汉大学学报(信息科学版)》2008,33(2):183-186

从观测量分组的参数平差出发,详细推导了附加约束条件的序贯平差及其精度估计,讨论了附加约束条件的抗差序贯平差的计算过程.算例表明,推导的公式正确有效,简单实用,附加约束条件的序贯平差抗差估计能有效地抵制粗差的影响.  相似文献   

Dynamic data integration for structural modeling: model screening approach using a distance-based model parameterization   总被引：2，自引：0，他引：2  

Satomi Suzuki  Guillaume Caumon  Jef Caers 《Computational Geosciences》2008,12(1):105-119

This paper proposes a novel history-matching method where reservoir structure is inverted from dynamic fluid flow response. The proposed workflow consists of searching for models that match production history from a large set of prior structural model realizations. This prior set represents the reservoir structural uncertainty because of interpretation uncertainty on seismic sections. To make such a search effective, we introduce a parameter space defined with a “similarity distance” for accommodating this large set of realizations. The inverse solutions are found using a stochastic search method. Realistic reservoir examples are presented to prove the applicability of the proposed method.  相似文献   

我国风云极轨气象卫星及应用进展     

何锡玉  蔡夕方  朱亚平  张雷 《气象科学进展》2021,(1)

我国风云极轨气象卫星数据,目前已经被应用在天气预报、气候预测、自然灾害、环境监测、科学研究等多个重要领域,为我国国民经济建设、国防建设、防灾减灾和全球许多国家的经济发展做出了重要贡献。本文介绍了我国风云极轨气象卫星的发展历程,重点阐述了目前风云极轨气象卫星在卫星数据预处理、定量产品反演、卫星资料同化等方面的应用研究进展,并展示了第二代风云极轨气象卫星在全球业务观测、大气三维探测、海洋环境监测、数值预报应用等相关典型应用。在国家创新战略发展框架下,根据“国家级气象现代化总体方案”确定的2020年气象卫星及应用发展目标,第二代极轨气象卫星风云三号03批卫星系统工程必将进一步发挥重大支撑作用。  相似文献   

Characterizing heterogeneous permeable media with spatial statistics and tracer data using sequential simulated annealing     

Akhil Datta-Gupta  Larry W. Lake  Gary A. Pope 《Mathematical Geology》1995,27(6):763-787

Characterizing heterogeneous permeable media using flow and transport data typically requires solution of an inverse problem. Such inverse problems are intensive computationally and may involve iterative procedures requiring many forward simulations of the flow and transport problem. Previous attempts have been limited mostly to flow data such as pressure transient (interference) tests using multiple observation wells. This paper discusses an approach to generating stochastic permeability fields conditioned to geologic data in the form of a vertical variogram derived from cores and logs as well as fluid flow and transport data, such as tracer concentration history, by sequential application of simulated annealing (SA). Thus, the method incorporates elements of geostatistics within the framework of inverse modeling. For tracer-transport calculations, we have used a semianalytic transit-time algorithm which is fast, accurate, and free of numerical dispersion. For steady velocity fields, we introduce a transit-time function which demonstrates the relative importance of data from different sources. The approach is illustrated by application to a set of spatial permeability measurements and tracer data from an experiment in the Antolini Sandstone, an eolian outcrop from northern Arizona. The results clearly reveal the importance of tracer data in reproducing the correlated features (channels) of the permeability field and the scale effects of heterogeneity.  相似文献   

A way to synchronize models with seismic faults for earthquake forecasting: Insights from a simple stochastic model     

lvaro Gonzlez  Miguel Vzquez-Prada  Javier B. Gmez  Amalio F. Pacheco 《Tectonophysics》2006,424(3-4):319

Numerical models are starting to be used for determining the future behaviour of seismic faults and fault networks. Their final goal would be to forecast future large earthquakes. In order to use them for this task, it is necessary to synchronize each model with the current status of the actual fault or fault network it simulates (just as, for example, meteorologists synchronize their models with the atmosphere by incorporating current atmospheric data in them). However, lithospheric dynamics is largely unobservable: important parameters cannot (or can rarely) be measured in Nature. Earthquakes, though, provide indirect but measurable clues of the stress and strain status in the lithosphere, which should be helpful for the synchronization of the models.The rupture area is one of the measurable parameters of earthquakes. Here we explore how it can be used to at least synchronize fault models between themselves and forecast synthetic earthquakes. Our purpose here is to forecast synthetic earthquakes in a simple but stochastic (random) fault model. By imposing the rupture area of the synthetic earthquakes of this model on other models, the latter become partially synchronized with the first one. We use these partially synchronized models to successfully forecast most of the largest earthquakes generated by the first model. This forecasting strategy outperforms others that only take into account the earthquake series. Our results suggest that probably a good way to synchronize more detailed models with real faults is to force them to reproduce the sequence of previous earthquake ruptures on the faults. This hypothesis could be tested in the future with more detailed models and actual seismic data.  相似文献   

Speciation analysis and significance of ecological geochemistry     

Yaping WANG Chunxue XU Ziyi AN Suming WANG 《中国地球化学学报》2006,25(B08):205-205

Different species of one element have different activities, so it has different effects on environment and human health. To analyze qualitatively and quantitatively the speciation of a special element in sample, which is the important basis for appraising the toxicity and studying the rule of transfer and translation of elements. Since the 1970＇s, the scheme of sequential extraction has already been used at many laboratories both at home and abroard, to get the information about heavy metals＇ activity in polluted soils. Because this method has the experimental nature, many schemes of problem has taken place, the absence of consistency of these sequential extraction have been formed. Thus the complexity of the schemes, the lack of selectivity of reagent, the lack of quality control, the result mainly related to the extraction scheme used, and so on. In the face of these problems, the study of experimental methods of sequential extraction on three different soils, sediment in Dongting Lake, soil in Jiangsu Province and loess in Shanxi Province was made. Reference materials of heavy metal speciation following sequential extraction in soil and sediment had been developed. Nowadays two kinds of sequential extraction methods which are widely used are BCR （three steps） and improved Tessier methods （seven steps）. Based on three steps of BCR, water-soluble speciation and the residual speciation were increased in our research. BCR701 was determined eight times at different laboratories using BCR three steps. The results showed that determined data obtained eight times were identical to the standard value, and it is indicated that this method has good reproducibility. The stability and homogeneity experiments indicated that the preparation of three types of candidates accorded with our requirements. Eight laboratories had afforded the determined values of 12 heavy metal elements （Cu, Pb, Zn, Mn, Co, Ni, Cd, Cr, Mo, As, Sb, Hg, Se et al.） using BCR three steps. Also, these three candidates afforded the determined values by seven steps, and 12 laboratories had participated.  相似文献