Interannual changeability in the variations of the vertical component of the electric field in Lake Baikal

The long-term deep-water measurements of the vertical component of the electric field on a surface-lakebed base revealed unexpectedly high interannual changeability in the amplitudes of its variations in periods ranging from a few hours to several months. This changeability almost equally affects the field components caused by the induction in the water flows and, supposedly, by the closing current of the global electric circuit above the rift fault. We present the evidence for the correlation of this effect with the interannual variability in meteorological activity. However, the physical background of this correlation is trivial only for the electric component associated with the induction and still remains unclear for the field component caused by the closing current, which has much higher amplitude.     

Assimilation of climatic hydrological data in a Black-Sea model based on the algorithm of adaptive statistics of prognostic errors

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.     

Assimilation of the climatic hydrological data in the σ-coordinate model of the black sea by the algorithm of adaptive statistics

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.     

Manifestation of Variations of Solar X-Ray Radiation in the Vertical Component of the Electric Field in Lake Baikal

Geomagnetism and Aeronomy - Data from a long-term experiment with monitoring of the vertical component of the electric field at the base from the surface to the bottom showed oscillations with...     

Hydrological and morphological processes at the Zhujiang River mouth area, China

Hydrological and morphological processes in the Zhujiang River (Pearl River) mouth area of China are discussed. The hydrological regime of the Xijiang River, which is the largest river of South China and the main source of water inflow into the Zhujiang mouth area, is described. The basic features of the hydrological regime of the delta and the near-shore zone of the Zhujiang River mouth are characterized, much attention being given to the role of tides and mixing of river and sea water in the hydrological regime. Special emphasis is placed on morphodynamic processes at the mouth area and the history of the Zhujiang Delta evolution.     

Radiating Vortices in Geophysical Fluid Dynamics

The dynamics of a single vortex on a beta-plane is discussed in this paper. A barotropic, an equivalent barotropic, one-and-a half and two-layer models are considered. The momentum and energy balances are used to describe the evolution of a vortex. A quasi-stationary balance of the Rossby, Zhukovsky-Kutta forces and the force induced by Rossby-wave radiation, describes the dynamics of the barotropic vortex. A net Coriolis force occurs if the fluid is stratified. The difference between the dynamics of cyclones and anticyclones results directly from the Coriolis force acting on a single vortex in a stratified fluid.All vortices radiate Rossby waves in the quasigeostrophic approximation but intense anticyclones propagate steadily in a one-and-a half layer model. A critical amplitude that bounds radiating and steadily propagating anticyclones is found. Steady propagation of anticyclones in general is impossible in a two-layer fluid due to the radiation of a barotropic Rossby-wave. Some solutions of solitary wave type which are known for a two-layer model, survive owing to wave interference.A single vortex can extract energy from a Rossby wave if synchronism conditions are satisfied. The wave interference again plays a crucial role in this case. The wave interference also determines the energy exchange of vortices located at larger distances. If the distance between the vortices is shorter than the length of the radiated waves, modon may be formed due to a small energy loss.The unbounded monotonic variation of the planetary vorticity is a characteristic feature of a beta-plane approximation. As a result, a single vortex propagates up to a 'rest latitude' where it disappears. The evolution of a single barotropic vortex over bottom topography provides another example of a background vorticity distribution with a local extremum above hills (valleys) or ridges (troughs). Physics of its movement differs from a beta-plane case, but if a vortex lies over broad topography, equations are similar and the evolution of a vortex manifests the same typical features. Particularly, a cyclonic vortex tends to drift to the top of a hill or a ridge. An anticyclonic vortex, on the contrary, slides to the bottom of a valley or a trough.An interaction of a barotropic vortex with a broad mean flow is tractable qualitatively on the basis of previous results. Numerical examples illustrating absorption of a small vortex by a larger one and a vortex movement across the flow, are direct analogies of the vortex evolution over a hill and a ridge, respectively. At the same time, strong influence of strain drastically changes the vortex structure.     

Lagrangian Transport by Currents Variable in Time in the Model of Wind-Induced Circulation of the Black Sea

We construct a simple model of seasonal variability of circulation in the Black Sea, which satisfactorily explains the data of altimetric satellite observations. The model is used to describe the nonstationary wind-induced currents in a round basin and study the trajectories of water particles in the surface layer of the sea. It is shown that, for nonstationary currents, these trajectories can be quite complicated. It is also assumed that Lagrangian mixing can be caused by the complex trajectories of water particles.     

Seasonal deformation of the North Equatorial Countercurrent in the Atlantic Ocean

The geostrophic circulation of active and intermediate layers in the north Tropical Atlantic is analysed on the basis of data collected in the transatlantic study area in 1986–1987. Its seasonal features are also found. Quasi-steady eddy formations and their relation to the bottom topography are considered for the intermediate region. The influence of these formations on the kinematics of large-scale currents in this layer is substantiated. Structures of large-scale tropical cyclonic and anticyclonic eddy formations are specified. A strategy for further studies in the Tropical Atlantic is suggested.Translated by Mikhail M. Trufanov.