Numerical experiments with data assimilation in the simplest dynamic-stochastic model for the ocean's synoptic variability closed at the level of the second moments

The results of numerical experiments with data assimilation in a non-linear model of the synoptic dynamics of the world's oceans are reported. The model's response to the data assimilation is studied at different values of the relative error in determining the initial fields and assimilation discreteness. The results of application of the algorithms of optimum filtration and optimum interpolation are compared. The advantages of the filtration algorithm employed are discussed only for the case of small errors in determining the initial fields and low assimilation discreteness. The possibility of deterioration of the prediction estimates in data assimilation with discreteness less than the typical time of variability of the average fields is noted.Translated by Mikhail M. Trufanov.     

Assessment of the effectiveness of POLYMODE data assimilation by a numerical barotropic model for synoptic motions

This paper considers the results of numerical experiments involving POLYMODE data assimilation by a barotropic model for synoptic ocean dynamics. The model's response the data assimilation for various space-time discretenesses of assimilation is studied. Results derived from the application of optimal interpolation algorithms and modified optimal filtration algorithms are compared. Qualitative similarity to the calculations carried out through the simulation modelling technique is noted. Optimal assimilation algorithms are determined, depending on the space-time discreteness used. An optimal sampling discreteness for the POLYMODE conditions is suggested.Translated by Vladimir A. Puchkin.     

Evolution equation for the error correlation function of vorticity prediction used by a barotropic synoptic motion model to assimilate data

An exact equation is derived for the error correlation function of model processes, governed by a barotropic vortex balance equation in a linear approximation. This equation can be effectively applied to assimilate data with small spatial-temporal discreteness when the assumption on error correlation function's stationarity (homogeneity, isotropicity) proves to be incorrect and leads to unsatisfactory results.Translated by Vladimir A. Puchkin.     

Cretaceous Rocks of the Penzhina Bay: Mineralogy,Petrography, and Geodynamic Sedimentation Conditions

Cretaceous sedimentary and volcanosedimentary rocks from northwestern Kamchatka are considered. The stadial analysis has revealed variable impacts of three major provenances upon the Cretaceous Penzhina sedimentary basin. The provenances were composed of volcanic and volcanosedimentary rocks (Uda–Murgal island arc and Okhotsk–Chukotka volcanic belt) and granitic–metamorphic rocks (the mature Asian continental margin). Sediments were largely accumulated owing to the erosion of island-arc volcanics during reactivation of the Uda–Murgal island arc (Hauterivian–Barremian) or the Okhotsk–Chukotka volcanic belt (middle Albian–Cenomanian). Eroded granitic–metamorphic rocks of the mature Asian continental margin (Berriasian–Valanginian) or Asian metamorphic–volcanic rocks (Santonian–Campanian) were supplied to the basin during tectonically quiet periods (Berriasian–Valanginian and late Cenomanian–Campanian). Compositional changes in provenances were related to active tectonic processes at the continental margin, including evolution and closure of the Uda–Murgal island-arc system and origin of the Okhotsk–Chukotka volcanic belt. The postsedimentary modification of Cretaceous rocks deposited in forearc trough beyond the tectonically active accretionary prism is characterized by a low degree of clastic component alteration.     

Effectiveness of data assimilation using probabilistic techniques in a model for synoptic velocity field evolution

The results of numerical experiments involving data assimilation by linear and non-linear models for synoptic ocean dynamics are presented. This paper considers the model's response to data assimilation at diverse values of the relative error in the determination of the initial fields and space-time discreteness of data assimilation. The data obtained using the optimal filtering are compared with those provided by the optimal interpolation (OI). A qualitative difference in the response of the linear and non-linear models to data assimilation is noted. The limiting values of the time-space discreteness of observations assimilation are determined, which allow correct application of OI.Translated by Vladimir A. Puchkin.     

Optimization of the data assimilation algorithm in a model for synoptic dynamics of the velocity field

The results of numerical experiments involving data assimilation by a non-linear model for synoptic dynamics of the ocean are given. The results of application of simplified optimal filtration algorithms (with the correlation error function being parametrized for both linear and non-linear variants) and of the optimal interpolation are intercompared. The use of a non-linear equation to predict average values and a linear one to predict dispersion in the filtration algorithm is suggested as most appropriate for the cases, when anisotropy of the correlation function is to be included. In other cases, it is considered worth-while to apply optimal interpolation.Translated by V. Puchkin.     

Formation of gas hydrate deposits in the Siberian Arctic shelf

Natural gas hydrate deposits have been estimated to store about 10% of gas in hydrate form (even with regard to a higher concentration of gas in hydrates), proceeding from the known ratio of dissolved-to-deposited gas. This high percentage is largely due to the fact that the buffer factor in natural gas hydrate deposits is lower than that for free gas because of less diverse structural conditions for gas accumulation. Therefore, the available appraisal of world resources of hydrated gas needs a revision.Hydrates in rocks are either syngenetic or epigenetic. Syngenetic hydrates originate from free or dissolved gas which was present in rocks in situ at the time when PT-conditions became favorable for gas hydrate formation. Epigenetic hydrates are derived from gas which came by migration into rocks with their PT-conditions corresponding to formation of gas hydrates.In addition to the optimum PT-conditions and water salinity, economic gas hydrate accumulation requires sustained supply of natural gas into a specific zone of gas hydrate formation. This condition is feasible only in the case of vertical migration of natural gas along faults, fractured zones, and lithologic windows, or, less often, as a result of lateral migration.Of practical importance are only the gas hydrate deposits produced by vertical or lateral gas migration.     

Level of Lake Ladoga at Possible Climate Changes

A transfer function model with climatic indices as the input and the lake level as the output is proposed to describe the response of a lake to climate changes. The climate indices include air temperature and atmospheric precipitation. The model is used to assess the response of the Lake Ladoga level to different climate changes. It is shown that the significant deviations of the lake level from the values corresponding to the modern climate are associated with changes in the numerical characteristics of climate indices and can be attributed to the displacement of the boundaries of climatic seasons. In this case, significant changes in the lake level may take place even without visible deviations of the annual averages of temperature and precipitation from their long-term standards.     

A simple numerical dynamic-stochastic model of the ocean's synoptic variability closed at the second moment level

The results of numerical experiments involving a dynamic-stochastic model closed at the second moment level are reported. Specific features of the model are the possibility of using it neglecting viscosity coefficients, as well as in energy and enstrophy conservation at the prediction stage. The model is fairly effective in saving computer time. The model prognostic fields are less smoothed than those produced by a model with similar characteristics of the computed grid area and with biharmonic viscosity.Translated by Vladimir A. Puchkin.