Patterns of spatial distribution of positive thunderstorm discharges in Eastern Siberia

Patterns of spatial distributions of the thunderstorm positive discharges, which were obtained by using a one-point storm direction and distance finder with observation radius of ～1200 km in Eastern Siberia in 2003–2007, are considered in this paper. It was found that distributions of positive discharges reflect, in general, overall patterns of thunderstorm activity. Two centers corresponding to maximum activity of the negative storm discharges are located in southwest; however, they were dominating (in terms of their intensity) only in 2005. Two other centers are more intense: the northeastern one was especially strong in 2003, 2004, 2006 and the eastern one was dominating in 2003 and 2007. The northeastern centers are the most active in the beginning and the end of the season. In these areas, ratio of positive and negative discharge fluxes can exceed 1. Activity of the eastern center, whose large part is situated in mountains, can be explained by neighborhood of the Sea of Okhotsk. The mentioned patterns of spatial distributions of positive storm discharges indicate that the geographic conditions play a significant role in their origination in the eastern part of Siberia. In the southern and western regions, a typical electric structure of thunderstorm clouds develops with main negative charge in the lower part of a cloud. At the same time, in the high latitudes, in the mountains, evidently, a different mechanism is realized, leading to the inverted location of charges in a cloud.     

Numerical stochastic simulation of the solar cycle and quasi-biennial oscillation of wind speed in the equatorial stratosphere

A problem of simulation of a stationary random process (SRP) is studied. A computer program is developed for modeling SRP, should the parameters required be estimated beforehand. The programming methods used are well known, but the numerical scheme of modeling the SRP needs some explanations; therefore, it is considered in detail in the article, being its basic subject for consideration, although basic characteristic features of the program are also considered. Examples show how the program is used to simulate the solar cycle and the quasi-biennial oscillation of the solar wind in the equatorial stratosphere (QBO). A distinguishing feature of this work, compared with the previous one, is also simulation of the solar cycle taking into account the variability of the sunspot dispersion. The SRP parameters are estimated for the QBO. It is found that the annual mean wind speed variation behavior is similar to the SRP.     

Losses of birch foliage due to insect herbivory along geographical gradients in Europe: a climate-driven pattern?

The study reports large-scale geographical variation in foliar damage of Betula pubescens and B. pendula by leaf-chewing and leaf-mining insects in Northern and Central Europe. The data were obtained in late summer of 2004 from 90 study sites located along several latitudinal and longitudinal gradients up to 1275 km in length; repeatability of a pattern detected was checked in 2005. Foliar damage in B. pubescens due to endemic herbivory increased in Fennoscandia from 1–2% at 70°N to 5–7% at 60°N; this pattern was best explained by mean July temperatures. Higher foliar losses in southern Fennoscandia were mostly due to an increase in proportion of damaged leaves, while an average consumption per damaged leaf increased only slightly. Foliar damage in B. pendula in Fennoscandia followed the same pattern as described for B. pubescens, although the overall loss of leaf area was only ca. 70% of that in B. pubescens. In contrast, there was no geographical or climatic pattern in damage of B. pendula by insect herbivores in Central Europe; average foliar losses were around 5% between 48°N and 60°N. These data suggest that damage of northern birch forests by leaf-chewing and leaf-mining insects will at least double with expected climatic warming, while in more southern regions the effects of climate change on birch foliar losses due to insect herbivory may be small or even negligible.     

Spatial and Statistical Variability Analyses of Satellite-Based Climatic Data in Mereb-Gash Basin

Water Resources - Global reanalysis products are extensively used for hydrologic applications in sparse data regions. The establishment of some inputs for hydrologic modelling from global...     

New paleomagnetic data from Late Neoproterozoic sedimentary successions in Southern Urals,Russia: implications for the Late Neoproterozoic paleogeography of the Iapetan realm

We present the results of paleomagnetic study of Ediacaran sedimentary successions from the Southern Urals. The analysis of the sedimentary rocks of the Krivaya Luka, Kurgashlya and Bakeevo Formations reveal stable mid-temperature and high-temperature remanence components. Mid-temperature components were acquired during Devonian (Bakeevo Formation) and Late Carboniferous–Early Permian remagnetization events. The high-temperature components in Kurgashlya and Bakeevo Formations are interpreted to be primary, because they are supported by a positive conglomerate test (Bakeevo Formation) and magnetostratigraphic pattern (Kurgashlya Formation). The high-temperature component in the Krivaya Luka Formation is interpreted to be a Late Ediacaran overprint. Our new paleomagnetic poles together with some previously published Ediacaran poles from Baltica and Laurentia are used herein to produce a series of paleogeographic reconstructions of the opening of the Iapetus Ocean.     

Estimate of heat flux at the ice-water interface in Lake Baikal from experimental data

An original system for measuring temperature in the ice cover and subglacial water and an increase in the ice thickness provides data necessary for calculation of the heat flux at the ice-water interface. Successive freezing of 1-mm temperature sensors during the ice growth allows us to measure temperature gradients in the vicinities of the ice-water interface for the first time. An analytical equation derived from the Stefan condition allows calculations of the heat flux at the phase boundary on the basis of the experimental data, which agree with independent estimates that have been made on the basis of the subglacial temperature gradients and are within the 4–39 W/m² range. The flow at the ice-water interface is comparable with the heat flux inside the ice depth and significantly affects the dynamics of the ice cover thickness.     

Geodynamics of the Russian Arctic Shelf and Relief-Forming Processes in the Central Kara Basin

Oceanology - The article deals with the issues of the geodynamic evolution of the Kara–Barents Sea shelf and influence of structure-forming processes on the nature of relief formation. The...     

Regularities of ore formation in mid-ocean ridges

The regularities of the concentration of ore matter in the mid-ocean ridges are considered, and the mechanisms of hydrothermal and cumulative treatment of the crust by ore elements are substantiated.