Discussion of the Problem of Ionospheric Precursors of Magnetic Storms

Geomagnetism and Aeronomy - The problem of disturbances of the parameters of the F2 layer and the upper ionosphere during the days preceding the beginning of a magnetic storm has already been known...     

Changes in the climate and sea ice of the Northern Hemisphere in the 20th and 21st centuries from data of observations and modeling

The shrinking of the area occupied by sea ice in the Northern Hemisphere accelerated at the end of the 1990s, when the record minima of the summer area were successively noted, and its absolute minimum was observed in September 2007. Such a radical decrease is ahead of the projections of global models and provokes interest in the reliability of model calculations of the future of Arctic sea ice. The results of an analysis of the relation between the warming in the Arctic and the ice extent shrinkage from data of observations and modeling by an ensemble of global climate models are presented.     

Polar meteorology: The results of Russian research in 2003–2006

This publication is a review of the results of Russian polar studies performed in 2003–2006. It is based on material prepared by the Commission on Polar Meteorology of the National Geophysical Committee, Russian Academy of Sciences, and included in the National Report on Meteorology and Atmospheric Sciences to the XXIV General Assembly of the International Union of Geodesy and Geophysics, Perugia, Italy, July 2–13, 2007.     

Estimates of relaxation times in numerical dynamical models of open star clusters

Relaxation times in the spaces of several stellar-motion parameters are obtained for a number of open-cluster models. The differences between the relaxation times in these spaces increase with the degree of nonstationarity of the cluster models. In the course of the cluster’s evolution, the relaxation times increase in all the spaces considered. During violent relaxation, the stars occupy all domains accessible to them, first in absolute velocity and then in clustercentric distance. The dependence of the coarse-grained phase-space density of the cluster on small initial perturbations of the phase-space coordinates of its constituent stars tends to decrease at times exceeding the time scales for violent and “collisional” relaxation.     

Energy parameters of deep fluid systems

Doklady Earth Sciences -     

Letter to the editor

Using a method suggested by the authors earlier, the long-term trends of the F2-layer critical frequency, foF2 are derived for a set of ionospheric stations with a wide latitudinal and longitudinal coverage. All the trends are found to be negative. A pronounced dependence on geomagnetic latitude is found, the trend magnitude increasing with the latter. No globe scale longitudinal effect in trends is detected. For the majority of the stations there is also a pronounced seasonal effect, the trend magnitude being higher in summer than in winter.     

Evaluation of a Finite-Element Sea-Ice Ocean Model (FESOM) set-up to study the interannual to decadal variability in the deep-water formation rates

The characteristics of a global set-up of the Finite-Element Sea-Ice Ocean Model under forcing of the period 1958–2004 are presented. The model set-up is designed to study the variability in the deep-water mass formation areas and was therefore regionally better resolved in the deep-water formation areas in the Labrador Sea, Greenland Sea, Weddell Sea and Ross Sea. The sea-ice model reproduces realistic sea-ice distributions and variabilities in the sea-ice extent of both hemispheres as well as sea-ice transport that compares well with observational data. Based on a comparison between model and ocean weather ship data in the North Atlantic, we observe that the vertical structure is well captured in areas with a high resolution. In our model set-up, we are able to simulate decadal ocean variability including several salinity anomaly events and corresponding fingerprint in the vertical hydrography. The ocean state of the model set-up features pronounced variability in the Atlantic Meridional Overturning Circulation as well as the associated mixed layer depth pattern in the North Atlantic deep-water formation areas.     

Geomagnetic activity as a reflection of processes in the magnetospheric tail: 2. Plasma convection model

A model of plasma convection in the magnetospheric tail was developed. Although highly simplified, the model adequately describes the main characteristics of the process. We have calculated the physical parameters characterizing the magnetotail, as well as described the convection of fluxtubes in it and the process of electron dropout. The model explains the semiannual variation in magnetic activity.     

On the impact of atmospheric vs oceanic resolutions on the representation of the sea surface temperature in the South Eastern Tropical Atlantic

Climate Dynamics - Despite the efforts of the modelling community to improve the representation of the sea surface temperature (SST) over the South Eastern Tropical Atlantic, warm biases still...