Spatial response of two European atmospheric circulation classifications (data 1901–2010)

Air pressure field and circulation pattern frequencies were investigated to (1) locate and compare positions of the underlying pressure fields, (2) analyse the spatial dimension of affected areas, (3) create schematic maps of important circulation types and (4) compare the classification types in their response to the data. Two manual classifications were used, selected for the length of their time series and their applicability to a larger region: the Grosswetterlagen classification (GWLc) and the Vangengeim–Girs classification (VGc). Their time series were correlated with a global set of gridded monthly sea-level pressure data. Results show the different conceptual orientation of VGc (hemispheric) and GWLc (continental). The highest correlation values and the largest affected areas are visible in winter, where patterns frequently extended into northern Africa and western Asia. Schematic maps, illustrating the average location of main pressure centres, are provided for basic classes of both classifications. Re-arranging GWLc subtypes increases the classifications comparability with the VGc. Analysis of moving correlation coefficients reveals high fluctuations in the relation of both classifications over time.     

Variability and trends in daily minimum and maximum temperatures and in the diurnal temperature range in Lithuania,Latvia and Estonia in 1951–2010

Spatial distribution and trends in mean and absolute maximum and minimum temperatures and in the diurnal temperature range were analysed at 47 stations in the eastern Baltic region (Lithuania, Latvia and Estonia) during 1951–2010. Dependence of the studied variables on geographical factors (latitude, the Baltic Sea, land elevation) is discussed. Statistically significant increasing trends in maximum and minimum temperatures were detected for March, April, July, August and annual values. At the majority of stations, the increase was detected also in February and May in case of maximum temperature and in January and May in case of minimum temperature. Warming was slightly higher in the northern part of the study area, i.e. in Estonia. Trends in the diurnal temperature range differ seasonally. The highest increasing trend revealed in April and, at some stations, also in May, July and August. Negative and mostly insignificant changes have occurred in January, February, March and June. The annual temperature range has not changed.     

Deep slices and the Supercluster-Void Network

We compare the properties of superclusters of Abell clusters with those of superclusters of loose groups from the Las Campanas Redshift Survey. We show that supercluster intersections with the LCRS slices coincide with the high-density regions of the galaxy distribution. The orientation of superclusters in respect of line-of-sight is nearly random, with a slight excess of systems oriented perpendicularly to the line of sight.     

Field observations on hydrodynamic and coastal geomorphic processes off Harilaid Peninsula (Baltic Sea) in winter and spring 2006–2007

Investigations of multi-layer current regime, variations in sea level and wave parameters using a bottom-mounted RDCP (Recording Doppler Current Profiler) during 20 December 2006–23 May 2007 were integrated with surveys on changes of shorelines and contours of beach ridges at nearby Harilaid Peninsula (Saaremaa Island). A W-storm with a maximum average wind speed of 23 m s⁻¹ occurred on 14–15 January with an accompanying sea level rise of at least 100 cm and a significant wave height of 3.2 m at the 14 m deep RDCP mooring site. It appeared that in practically tideless Estonian coastal waters, Doppler-based “vertical velocity” measurements reflect mainly site-dependent equilibrium between resuspension and sedimentation. The mooring site, 1.5 km off the Kelba Spit of Harilaid, was located in the accumulation zone, where downward fluxes dominated and fine sand settled. As a result of storms in January and April, the distal part of the accumulative gravel spit advanced by 50 m, whereas a 30–50 m retreat of the shoreline in the western and northern parts occurred at Cape Kiipsaare. The location of the beach ridges shows that the development of the spit occurs through relatively short-period but infrequent storm events, roughly 2–3 times each decade.     

Biophysical impacts of climate change on some terrestrial ecosystems in Estonia

Climate warming due to the enhanced greenhouse effect is expected to have a significant impact on the natural environment and human activity in high latitudes. Because of its geography, wide coastal areas, water resources, forests, and wetlands, the environment of Estonia is sensitive to climate change and sea level rise. Climate change scenarios for Estonia were generated using a Model for the Assessment of Greenhouse-gas Induced Climate Change (MAGICC) and a regional climate change database, Scenario Generator (SCENGEN). Three alternative emission scenarios were combined with data from 14 general circulation model experiments. The assessment results of forest resources using RipFor, a forest-soil-atmosphere model, show that climate warming would enhance forest growth in Estonia resulting in increased productivity (2–9%) of harvestable timber on highly productive sites. Nutrient mobility increases greatly and in highly permeable soils with stable vegetation, increased mobility may result in nutrient losses through leaching. The assessment results of water resources using the simple water balance model, WatBal, show that the runoff regime of Estonian rivers would equilibrate and the groundwater table would rise. Climate warming would not cause any particular problems with water supply but the groundwater quality may suffer from increased leaching. Due to milder winters and increased storminess, the destruction of coastal areas, inundation of wetlands and disappearance of rare plant communities in coastal areas would be the most damaging results of climate change. Most sandy beaches high in recreational value would disappear. However, isostatic uplift and settlements inland from the present coastline reduce the risk of socio-economic decline. This revised version was published online in July 2006 with corrections to the Cover Date.     

The effect of protective pillars on the deformation of mine shafts

Summary Mine shafts have traditionally been protected by leaving the ore in the immediate surroundings of the shafts in place as a pillar. Empirical rules are used to determine the dimensions of these protective pillars. The face element principle introduced by Salamon has been used to compute functions which express the influence of mining in a horizontal seam on the rock mass above it. Values have been calculated for the tilt, distortion, horizontal and vertical strain, curvature, and vertical stress along a shaft for various values of Poisson's ratio, seam depth, pillar radius, mining geometry, and closure over the mined area. The results are compared with those obtained using empirical ideas, particularly the angle of draw concept in determining pillar size. It appears that the depth of the seam is of major significance and that no pillar is needed for the protection of a shaft when the mined seam is beyond a certain depth. On the other hand it is possible, at all depths, to replace the protective action of a shaft pillar by other mining schemes. A significant amount of information which has been published on experience gained during the mining of shaft pillars tends to indicate that in many mines shaft pillars are excessively large.

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Zusammenfassung Schachtsicherheitspfeiler, die den Schacht vor Abbaueinwirkungen schützen sollen, werden gewöhnlich aufgrund von Erfahrungswerten bemessen.Die durch den Abbau in einem Flöz flacher Lagerung verursachten Einwirkungen auf einen saigeren Schacht sind hier nach dem Flächenelement-Prinzip ermittelt, wie Salamon es einführte. Entlang der Schachtsäule wurden die Schiefstellung, Verschiebung, horizontale und vertikale Dehnung, Krümmung und vertikale Spannung berechnet. Dabei wird der Einfluß der Querdehnungszahl, der Flöztiefe, des Pfeilerradius, der Form des Abbaufeldes und der Konvergenz im Flöz betrachtet. Diese Ergebnisse werden mit empirischen Regeln verglichen. Dabei ergab sich, daß die Tiefe des Flözes erhebliche Bedeutung hat und daß zum Schutze des Schachtes kein Pfeiler benötigt wird, wenn das abgebaute Flöz unterhalb einer bestimmten Teufe liegt. Auf der anderen Seite ist es für alle Tiefen möglich, den Schutz des Schachtes durch den Sicherheitspfeiler ersetzende geeignete Abbaumethoden zu gewährleisten.Manche Veröffentlichungen lassen erkennen, daß Schachtsicherheitspfeiler oft unnötig groß bemessen sind.

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Résumé En général la protection des puits est accomplie par l'abandon d'une partie du gisement, le stot de puits. Les dimensions des stots sont déterminées par des méthodes empiriques.Dans cette étude c'est la méthode proposée par Salamon qui est employée; il s'agit du calcul de l'influence de l'extraction d'un élément de taille sur les morts terrains supérieurs. Cette méthode permet de calculer les déformations, la pente, la distorsion, la courbure et les tensions le long du puits. L'influence de la profondeur de la couche, de la convergence, de l'aire exploitée, du diamètre du stot de protection et des caractéristiques mécaniques du terrain ont été considérées.Les résultats indiquent l'importance particulière de la profondeur du gisement. En effet, au-delà d'une certaine profondeur un stot de protection devient superflu. D'autre part l'influence de l'aire exploitée et de la convergence dans cette région sont telles qu'il est toujours possible de remplacer l'action protectrice du stot par une protection equivalente fournie par l'emploi d'un schèma d'exploitation bien choisi.Le nombre de cas où une exploitation partielle ou entière du stot de puits a eu lieu et où son influence sur la colonne du puits a été décrite est suffisant pour permettre d'affirmer qu'en général les dimensions du stot de puits sont trop importantes.

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With 11 Figures