共查询到20条相似文献，搜索用时 31 毫秒
1.
V. B. Zalesny A. V. Gusev S. N. Moshonkin 《Izvestiya Atmospheric and Oceanic Physics》2013,49(6):642-658
A numerical primitive-equation model of the hydrodynamics of the Black Sea and the Sea of Azov in σ-coordinates is proposed. The model has a resolution of ～4 × 4 km in horizontal coordinates with 40-σ levels in the vertical and includes the four-dimensional variational initialization of temperature and salinity fields. A numerical initialization algorithm combines splitting methods and adjoint equations. Flow, temperature, sea level, and salinity fields driven by atmospheric forcing are calculated for the year 2008. The calculations are made in a variational initialization — prediction regime. Temperature and salinity fields are initialized at the end of each month. The optimality system includes forward and adjoint transport-diffusion equations for heat and salt that are linearized on the assimilation interval. Results of three numerical experiments with different sets of assimilated data in comparison with the prediction obtained from the forward model are discussed. 相似文献
2.
V. B. Zalesny V. I. Agoshkov V. P. Shutyaev F. Le Dimet B. O. Ivchenko 《Izvestiya Atmospheric and Oceanic Physics》2016,52(4):431-442
Models and methods of the numerical modeling of ocean hydrodynamics dating back to the pioneering works of A.S. Sarkisyan are considered, with emphasis on the formulation of problems and algorithms of mathematical modeling and the four-dimensional variational assimilation of observational data. An algorithm is proposed for studying the sensitivity of the optimal solution to observational data errors in a seasurface temperature assimilation problem in order to retrieve heat fluxes on the surface. An example of a solution of the optimal problem of the World Ocean hydrodynamics with the assimilation of climatic temperature and salinity observations is offered. 相似文献
3.
Comparative analysis of the North Atlantic surface circulation reproduced by three different methods
K. V. Lebedev A. S. Sarkisyan O. P. Nikitin 《Izvestiya Atmospheric and Oceanic Physics》2016,52(4):410-417
Calculation results are presented for long-term mean annual surface currents in the North Atlantic based on direct drifter measurements and numerical experiments with the ocean general circulation model using both climatic arrays of hydrological data World Ocean Atlas 2009 and Argo profiling data. The calculations show that the technique suggested for model calculations of oceanographic characteristics of the World Ocean with the use of Argo data significantly improves the climatic fields of the temperature and salinity even on a coarse grid. The comparison of the model calculation results with drifter data showed that the temperature and salinity fields found from Argo data with the use of data variational interpolation on a regular grid allow the calculation of realistic currents and can be successfully used as initial conditions in hydrodynamic models of the ocean dynamics. 相似文献
4.
The problem of numerical modeling and analysis of the large-scale World Ocean circulation variability under variations of
the external forcing is considered. A numerical model was developed in the INM RAS and is based on the primitive equations
of the ocean circulation written in a spherical generalized σ-coordinate system. The model’s equations are approximated on
a grid with resolution of 2.5° × 2° × 33, and the North Pole is displaced to the continental point (60°E, 60.5°N). There are
two stages for the numerical experiments. The quasi-equilibrium circulation of the World Ocean under the climatological atmospheric
forcing is simulated at the first stage. The run is carried out over a period of 3000 years during which a quasi-equilibrium
model regime is formed. At the second stage, the sensitivity of the model ocean circulation to the atmospheric forcing perturbations
in the Southern Hemisphere is studied. According to the results, the strongest regional changes in the hydrography take place
in the Arctic Ocean. Substantial changes of sea’s surface height and local anomalies of the temperature and salinity are formed
there. 相似文献
5.
A regional ocean circulation model with four-dimensional variational data assimilation scheme is configured to study the ocean state of the Indian Ocean region (65°E–95°E; 5°N–20°N) covering the Arabian Sea (AS) and Bay of Bengal (BoB). The state estimation setup uses 10 km horizontal resolution and 5 m vertical resolution in the upper ocean. The in-situ temperature and salinity, satellite-derived observations of sea surface height, and blended (in-situ and satellite-derived) observations of sea surface temperature alongwith their associated uncertainties are used for data assimilation with the regionally configured ocean model. The ocean state estimation is carried out for 61 days (1 June to 31 July 2013). The assimilated fields are closer to observations compared to other global state estimates. The mixed layer depth (MLD) of the region shows deepening during the period of assimilation with AS showing higher MLD compared to the BoB. An empirical forecast equation is derived for the prediction of MLD using the air–sea forcing variables as predictors. The surface and sub-surface (50 m) heat and salt budget tendencies of the region are also investigated. It is found that at the sub-surface, only the advection and diffusion temperature and salt tendencies are important. 相似文献
6.
传统的四维变分数据同化方法在同化观测资料的同时可以对数值模式参数进行优化,然而传统的四维变分方法需要针对不同的数值模式编写特有的伴随模式,因此算法的可移植性差,同时计算时耗费大量资源。本文提出了一种新的基于解析四维集合变分的参数优化方法,该方法以迭代搜索得到的模式参数为基准展开扰动并构建样本集合,由此显式地计算协方差矩阵,并得到代价函数极小值的解析解,从而避免了伴随模式的使用。基于Lorenz-63模型对该方法进行单参数和多参数数值试验和优化效果检验,并在不同的同化时间窗口长度和观测采样间隔情况下,采用传统四维变分方法与之进行对比,结果显示,新方法表现出与传统四维变分相同的优化性能,都能有效收敛到真值,而新方法不需要计算伴随模式,可移植性好。本文还测试了不同的集合成员个数和模式参数真值的情况下新方法的同化效果,结果表明,新方法对集合样本个数及模型参数真值不敏感,采用较少的集合样本即可完成数据同化。 相似文献
7.
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
8.
V. I. Agoshkov V. M. Ipatova V. B. Zalesnyi E. I. Parmuzin V. P. Shutyaev 《Izvestiya Atmospheric and Oceanic Physics》2010,46(6):677-712
Problems of the variational assimilation of satellite observational data on the temperature and level of the ocean surface,
as well as data on the temperature and salinity of the ocean from the ARGO system of buoys, are formulated with the use of
the global three-dimensional model of ocean thermodynamics developed at the Institute of Numerical Mathematics, Russian Academy
of Sciences (INM RAS). Algorithms for numerical solutions of the problems are developed and substantiated, and data assimilation
blocks are developed and incorporated into the global three-dimensional model. Numerical experiments are performed with the
use of the Indian Ocean or the entire World Ocean as examples. These numerical experiments support the theoretical conclusions
and demonstrate that the use of a model with an assimilation block of operational observational data is expedient. 相似文献
9.
10.
The problem of simulating ocean general circulation is considered using an approach developed by G.I. Marchuk. Most attention is focused on problems associated with the application of multi-component-splitting and adjoint-equation methods and with the parameterization of turbulent-exchange processes. The statement of the problem, an algorithm of its solution, and the results of the four-dimensional temperature and salinity data assimilation in a model of World Ocean hydrodynamics are discussed. This algorithm yields qualitatively reliable results, and its main features are modularity, usability, and the possibility of using efficient implicit schemes. 相似文献
11.
A. A. Zelenko R. M. Vil’fand Yu. D. Resnyanskii B. S. Strukov M. D. Tsyrulnikov P. I. Svirenko 《Izvestiya Atmospheric and Oceanic Physics》2016,52(4):443-454
A new version of the ocean data assimilation system (ODAS) developed at the Hydrometcentre of Russia is presented. The assimilation is performed following the sequential scheme analysis–forecast–analysis. The main components of the ODAS are procedures for operational observation data processing, a variational analysis scheme, and an ocean general circulation model used to estimate the first guess fields involved in the analysis. In situ observations of temperature and salinity in the upper 1400-m ocean layer obtained from various observational platforms are used as input data. In the new ODAS version, the horizontal resolution of the assimilating model and of the output products is increased, the previous 2D-Var analysis scheme is replaced by a more general 3D-Var scheme, and a more flexible incremental analysis updating procedure is introduced to correct the model calculations. A reanalysis of the main World Ocean hydrophysical fields over the 2005–2015 period has been performed using the updated ODAS. The reanalysis results are compared with data from independent sources. 相似文献
12.
We propose an improvement of the algorithm of joint assimilation of the data on climatic temperature, salinity, and altimetric
sea level in a model of circulation. Unlike the previous works, the variances of the forecast errors of temperature and salinity
and the cross-covariance functions of of the forecast errors of salinity-level and temperature-level depend on the dynamics
of waters. It is shown that the structure of the fields of cross-covariance functions in the upper mixed layer is formed by
the vertical turbulent diffusion of the variances of forecast errors of temperature and salinity. At greater depths, these
statistical characteristics are mainly determined by the vertical advection. We compared the results of calculations with
and without taking into account the dynamics of the statistical characteristics. The analysis of the influence of the dynamics
of these characteristics makes it possible to reconstruct the mutually adapted climatic fields of temperature, salinity, and
horizontal and vertical current velocities in the Black Sea with the assimilation of data in the numerical model in each time
step.
Translated from Morskoi Gidrofizicheskii Zhurnal, No. 4, pp. 18–31, July–August, 2008. 相似文献
13.
We propose an algorithm of adaptive statistics of prognostic errors aimed at the assimilation of the climatic temperature
and salinity fields in a model of dynamics of the sea. The algorithm is used for the numerical solution of the proposed differential
equations for the dispersions of prognostic errors of temperature and salinity. The sources in the equations of advective
diffusion of heat and salt depend on the four-dimensional dispersions of prognostic errors and one-dimensional (along the
vertical coordinate) dispersions of measurement errors. The dispersions of prognostic errors are corrected at the times of
assimilation of the data. We perform the reconstruction and analysis of the climatic fields of currents in the Black Sea.
It is shown that the structure of the fields of dispersions in the upper mixed layer is determined by the vertical diffusion.
Below this layer, the distribution of dispersions depends on the vertical advection. The algorithm of adaptive statistics
of prognostic errors allows us to reconstruct the improved mutually adapted hydrophysical parameters with regard for the dynamics
of the dispersions of errors.
__________
Translated from Morskoi Gidrofizicheskii Zhurnal, No. 1, pp. 26–37, January–February, 2008. 相似文献
14.
S. N. Moshonkin A. V. Gusev V. B. Zalesny V. I. Byshev 《Izvestiya Atmospheric and Oceanic Physics》2016,52(2):196-206
Results of numerical experiments with an eddy-permitting ocean circulation model on the simulation of the climatic variability of the North Atlantic and the Arctic Ocean are analyzed. We compare the ocean simulation quality with using different subgrid mixing parameterizations. The circulation model is found to be sensitive to a mixing parametrization. The computation of viscosity and diffusivity coefficients by an original splitting algorithm of the evolution equations for turbulence characteristics is found to be as efficient as traditional Monin–Obukhov parameterizations. At the same time, however, the variability of ocean climate characteristics is simulated more adequately. The simulation of salinity fields in the entire study region improves most significantly. Turbulent processes have a large effect on the circulation in the long-term through changes in the density fields. The velocity fields in the Gulf Stream and in the entire North Atlantic Subpolar Cyclonic Gyre are reproduced more realistically. The surface level height in the Arctic Basin is simulated more faithfully, marking the Beaufort Gyre better. The use of the Prandtl number as a function of the Richardson number improves the quality of ocean modeling. 相似文献
15.
We realize the algorithm of adaptive statistics of forecasting errors for the assimilation of the climatic fields of temperature
and salinity in the σ-coordinate model of the dynamics of the Black Sea. The principal relations of this algorithm and its
simplified version based on the Kalman filter are presented. The distinctive features of realization of the algorithm specified
by the model are discussed. We also present the results of comparison of the hydrophysical fields of the Black Sea reconstructed
according to the algorithm of adaptive statistics and a simplified scheme of assimilation of the climatic data. It is shown
that the dependence of sources in the transport equations (heat and salt diffusion) on the four-dimensional variances of forecasting
errors and threedimensional measurement errors enables one to reconstruct the mutually adapted climatic parameters of the
sea more exactly. 相似文献
16.
A procedure for the four-dimensional (4D) analysis of the hydrophysical fields in the Black Sea with an assimilation of the temperature and salinity (T, S) data was realized on the basis of a numerical model which involves the primitive equations of motion, and the heat and salt advection equations. Two experiments were carried out which differed by the observation data assimilation procedure. Analysis has shown that the observation data assimilation procedure realized using the energy-balanced model allows the reproduction of some synoptic features of the circulation in the Black Sea. A comparison of two computations demonstrates the efficiency of assimilating the measurement data on the basis of the 4D analysis as compared with the sequential objective analysis.Translated by Mikhail M. Trufanov. 相似文献
17.
S. G. Demyshev V. V. Knysh G. K. Korotaev 《Izvestiya Atmospheric and Oceanic Physics》2006,42(5):555-567
A scheme of a periodic assimilation of climatic temperature and salinity data into a model is proposed. In accordance with the criteria chosen on the basis of numerical experiments, an optimum assimilation period of three hours is set. The proposed method allows a hydrodynamic adaptation of the fields of temperature, salinity, and flow velocity that are close to the climatic ones within the framework of the proposed criteria. The main feature of the adapted fields of vertical flows in the layer 0–700 m is their smooth character and an almost complete absence of small-scale noise. The extreme values of vertical velocity in this layer decrease by almost an order of magnitude as compared to analogous values calculated for the variant of data assimilation with a weak adjustment of fields. 相似文献
18.
V. V. Knysh S. G. Demyshev G. K. Korotaev A. S. Sarkisyan 《Izvestiya Atmospheric and Oceanic Physics》2007,43(3):363-377
A method for combined assimilation of climatic hydrologic fields of temperature, salinity, and the climatic dynamic level of the Black Sea into a model of sea dynamics is proposed. The monthly mean fields of the dynamic sea level were obtained from the results of assimilation of satellite altimetry data into the model. The statistical characteristics of errors in the forecasts of the level, salinity, and temperature were assumed to be proportional to the statistical characteristics of the differences between monthly mean climatic fields of temperature, salinity, and sea level calculated by means of assimilating altimetry observations of the sea level and analogous climatic hydrologic fields. The climatic fields of currents are reconstructed and analyzed. The assimilation of the climatic altimetry level allows the reproduction (in current fields) of quasi-stationary synoptic anticyclonic eddies located along the periphery of the Black Sea Rim Current. 相似文献
19.
Asynchronous data assimilation with the EnKF 总被引：3，自引：0，他引：3
This study revisits the problem of assimilation of asynchronous observations, or four-dimensional data assimilation, with the ensemble Kalman filter (EnKF). We show that for a system with perfect model and linear dynamics the ensemble Kalman smoother (EnKS) provides a simple and efficient solution for the problem: one just needs to use the ensemble observations (that is, the forecast observations for each ensemble member) from the time of observation during the update, for each assimilated observation. This recipe can be used for assimilating both past and future data; in the context of assimilating generic asynchronous observations we refer to it as the asynchronous EnKF. The asynchronous EnKF is essentially equivalent to the four-dimensional variational data assimilation (4D-Var). It requires only one forward integration of the system to obtain and store the data necessary for the analysis, and therefore is feasible for large-scale applications. Unlike 4D-Var, the asynchronous EnKF requires no tangent linear or adjoint model. 相似文献