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1.
Generalization of the approximation for the autocovariance function of estimate error, used frequently in four-dimensional analysis of the ocean's hydrophysical fields, is suggested for cross-covariance functions. It is shown that the principal properties of the covariance function of error estimate are not then violated. Approximation accuracy is studied through numerical experimentation using the two-dimensional equation for passive admixture transport as an example.Translated by V. Puchkin. 相似文献
2.
The effect of sea-ice extent in the North Atlantic on the stability of the thermohaline circulation in global warming experiments 总被引：1，自引：1，他引：1
Different climate models simulate different behavior of the Atlantic meridional overturning circulation (MOC) under the same global warming scenario. We propose a plausible explanation for this and argue that a proper simulation of the present-day climate in the subpolar North Atlantic is important. This is illustrated using results from idealized global warming experiments, in which both the radiative forcing scenario and the model employed are the same, with the only major difference being the initial subpolar North Atlantic climate. The initial conditions are made progressively colder, with more extensive sea-ice cover in the northern North Atlantic.The key result is that starting from conditions which are too cold in the North Atlantic and with sea-ice that is too extensive leads to an MOC that is more stable to the radiative forcing. Furthermore, under considerably underestimated sea surface temperatures in subpolar regions, the MOC can even intensify. A reduction of freshwater flux associated with the reduction of sea-ice melt is shown to be important for such unusual behavior of the MOC. Other mechanisms are also considered, but not deemed as important in explaining published inter-model differences. 相似文献
3.
A.E. Kontorovich L.G. Vakulenko V.A. Kazanenkov M.B. Skvortsov P.A. Yan V.V. Bykov A.Yu. Popov L.S. Saenko 《Russian Geology and Geophysics》2010,51(2):147-158
This study provides a comprehensive sedimentologic analysis of the J2 prospective horizon (Middle–Late Bathonian) in the central West Siberian Basin. Based on the extensive dataset, it was established that structural complexity of this horizon is largely caused by a variety of depositional environments. Sedimentary facies of this horizon pass upward from widespread continental at the base, through deltaic or coastal-continental, to marginal-marine at the top. Change in the paleohypsometry of the study area reflects the distribution of depositional environments, in terms of the proportions of continental, transitional, and marine deposits. The study also shows that facies variability and change in depositional settings can have a significant control on reservoir quality, as well as its vertical and lateral distribution. Using a combination of detailed GDE reconstructions, structure contour mapping on the top and base of the J2 horizon, analyses of well test data, probability of reservoir presence, distribution of average porosity and permeability within different subenvironments, a composite map showing variations in the reservoir effectiveness in the J2 horizon was generated. 相似文献
4.
We analyze the seasonal variability of the climatic hydrophysical fields of the Black Sea reporduced in three numerical experiments
carried out according to the model of circulation. The numerical predictions are performed for a period of 12.5 yr on the
basis of the hydrological data accumulated in 1983–1995. The monthly average climatic fields of the current speed are reconstructed
according to the data on the climatic fields of temperature and salinity by the method of hydrodynamic adaptation (standard).
It is shown that, in prognostic calculations, the seasonal variability of temperature and salinity is qualitatively close
to the “standard” dependence. At the same time, the quantitative difference between the climatic behavior of the model and
the standard dependence may be significant. The annual cycle of the currents is characterized by the intensification of the
Main Black-Sea Current in winter. The structure of the hydrophysical fields of the sea in the model becomes much more realistic
if it is based on the actual hydrological data.
Translated by Peter V. Malyshev and Dmitry V. Malyshev 相似文献
5.
Couldrey Matthew P. Gregory Jonathan M. Boeira Dias Fabio Dobrohotoff Peter Domingues Catia M. Garuba Oluwayemi Griffies Stephen M. Haak Helmuth Hu Aixue Ishii Masayoshi Jungclaus Johann Köhl Armin Marsland Simon J. Ojha Sayantani Saenko Oleg A. Savita Abhishek Shao Andrew Stammer Detlef Suzuki Tatsuo Todd Alexander Zanna Laure 《Climate Dynamics》2021,56(1-2):155-187
Sea levels of different atmosphere–ocean general circulation models (AOGCMs) respond to climate change forcing in different ways, representing a crucial uncertainty in climate change research. We isolate the role of the ocean dynamics in setting the spatial pattern of dynamic sea-level (ζ) change by forcing several AOGCMs with prescribed identical heat, momentum (wind) and freshwater flux perturbations. This method produces a ζ projection spread comparable in magnitude to the spread that results from greenhouse gas forcing, indicating that the differences in ocean model formulation are the cause, rather than diversity in surface flux change. The heat flux change drives most of the global pattern of ζ change, while the momentum and water flux changes cause locally confined features. North Atlantic heat uptake causes large temperature and salinity driven density changes, altering local ocean transport and ζ. The spread between AOGCMs here is caused largely by differences in their regional transport adjustment, which redistributes heat that was already in the ocean prior to perturbation. The geographic details of the ζ change in the North Atlantic are diverse across models, but the underlying dynamic change is similar. In contrast, the heat absorbed by the Southern Ocean does not strongly alter the vertically coherent circulation. The Arctic ζ change is dissimilar across models, owing to differences in passive heat uptake and circulation change. Only the Arctic is strongly affected by nonlinear interactions between the three air-sea flux changes, and these are model specific.
相似文献6.
The role of the Atlantic freshwater balance in the hysteresis of the meridional overturning circulation 总被引：1，自引：1，他引：0
We have studied the response of the Atlantic meridional overturning circulation to surface freshwater forcing using an ocean GCM coupled to an energy-moisture-balance atmosphere model. The overturning collapses rapidly when a slowly increasing forcing applied to the North Atlantic passes a positive threshold, and spins up equally quickly when the forcing falls below a negative threshold. This well-known behaviour is referred to as hysteresis because the thresholds in forcing are different for the transitions in opposite directions. However, we argue that the behaviour of the Atlantic salinity is more fundamental than the forcing. Hysteresis as a function of freshwater forcing occurs because the states with North Atlantic overturning on and off each tend to reinforce their associated salinity distributions and inhibit the transition to the other state. During the collapse, the Atlantic becomes less saline because of the import of 80 Sv year of freshwater by ocean transports across 30°S; during the spin-up this freshwater is exported again. We show that qualitatively similar hysteresis behaviour can be produced by perturbing the system without any net freshwater forcing. The salinity flip-flop is associated with the appearance and disappearance of a shallow reverse overturning circulation south of the Equator, which is present while the northern overturning is absent, and may provide the mechanism for the ocean freshwater influx during collapse. 相似文献
7.
A global, flux-corrected climate model is employed to predict the surface wind stress and associated wind-driven oceanic circulation
for climate states corresponding to a doubling and quadrupling of the atmospheric CO2 concentration in a simple 1% per year CO2 increase scenario. The model indicates that in response to CO2 increase, the position of zero wind stress curl in the mid-latitudes of the Southern Hemisphere shifts poleward. In addition,
the wind stress intensifies significantly in the mid-latitudes of the Southern Hemisphere. As a result, the rate of water
circulation in the subpolar meridional overturning cell in the Southern Ocean increases by about 6 Sv (1 Sv=106 m3 s−1) for doubled CO2 and by 12 Sv for quadrupled CO2, implying an increase of deep water upwelling south of the circumpolar flow and an increase of Ekman pumping north of it.
In addition, the changes in the wind stress and wind stress curl translate into changes in the horizontal mass transport,
leading to a poleward expansion of the subtropical gyres in both hemispheres, and to strengthening of the Antarctic Circumpolar
Current. Finally, the intensified near-surface winds over the Southern Ocean result in a substantial increase of mechanical
energy supply to the ocean general circulation. 相似文献
8.
The model numerical experiments on estimating the accuracy of two methods for solving the problem of Kalman smoothing, both iteration and precise, are described on the basis of a simple equation for the passive admixture transport. Some quantitative estimations are given.Translated by Mikhail M. Trufanov. 相似文献
9.
Yu. S. Saenko N. S. Natsvalyan N. Yu. Tepenitsyna 《Pure and Applied Geophysics》1988,127(2-3):335-352
A planetary model of the ionosphere and the protonosphere coupling is described. The system of three-dimensional nonstationary modeling equations of continuity and motion for the ions O+ and H+ is presented. Some numerical results of model calculations are compared with the experimental data. The important role of electromagnetic drifts in the formation of large-scale morphological peculiarities of the ionosphere and the protonosphere coupling is shown. 相似文献
10.
The use of the Kalman smoothing technique is suggested to handle an ocean diagnosis problem. It is shown that the variety of existing diagnostic techniques may be generalized, for which purpose the smoothing problem from the theory of optimal evaluation may be used.Translated by Vladimir A. Puchkin. 相似文献