The environmental effects of the installation and functioning of the submarine SwePol Link HVDC transmission line: a case study of the Polish Marine Area of the Baltic Sea

This paper describes the two-phase study of the environmental impact of the SwePol Link submarine electrical energy transfer system between Sweden and Poland. During the first phase (1997–1998), the potential effects of proposed technical solutions for the transmission line and different routes across the Baltic Sea were analysed. During the second phase (1999–2000), studies on environmental and background conditions before cable installation (1999) and studies on the environmental effects after cable system installation (2000) were undertaken. During this phase, underwater TV and video inspection of the bottom, observations of the bottom habitats by scuba-divers, sampling and laboratory analysis of macrozoobenthos and measurements of the earth's magnetic field were conducted.Underwater observations along the cable route indicated that one year after the cable had been laid no mechanical disturbances on the dynamic sandy bottom were visible. Studies of the bottom macrofauna indicated that there had been no significant changes in zoobenthos species composition, abundance or biomass which could have been clearly related to cable installation. Changes in the components of the magnetic field, although significant in the vicinity of the cable itself, did not exceed natural variability at a distance of 20 m.     

A numerical study of daily transitions in the convective boundary layer

We examine daily (morning–afternoon) transitions in the atmospheric boundary layer based on large-eddy simulations. Under consideration are the effects of the stratification at the top of the mixed layer and of the wind shear. The results describe the transitory behaviour of temperature and wind velocity, their second moments, the boundary-layer height Z _m (defined by the maximum of the potential temperature gradient) and its standard deviation σ _m , the mixed-layer height z _i (defined by the minimum of the potential temperature flux), entrainment velocity W _e, and the entrainment flux H _i . The entrainment flux and the entrainment velocity are found to lag slightly in time with respect to the surface temperature flux. The simulations imply that the atmospheric values of velocity variances, measured at various instants during the daytime, and normalized in terms of the actual convective scale w_*, are not expected to collapse to a single curve, but to produce a significant scatter of observational points. The measured values of the temperature variance, normalized in terms of the actual convective scale Θ_*, are expected to form a single curve in the mixed layer, and to exhibit a considerable scatter in the interfacial layer.     

The heat goes on—changes in indices of hot extremes in Poland

Theoretical and Applied Climatology - On the basis of temperature observations at 60 meteorological stations in Poland, changes in the indices associated with the presence of extremely high air...     

Statistics of Turbulence in the Stable Boundary Layer Affected by Gravity Waves

In order to investigate effects of interactions between turbulence and gravity waves in the stable boundary layer on similarity theory relationships, we re-examined a dataset, collected during three April nights in 1978 and in 1980 on the 300-m tower of the Boulder Atmospheric Observatory (BAO). The BAO site, located in Erie, Colorado, USA, 30 km east of the foothills of the Rocky Mountains, has been known for the frequent detection of wave activities. The considered profiles of turbulent fluxes and variances were normalized by two local, gradient-based scaling systems, and subsequently compared with similarity functions of the Richardson number, obtained based on data with no influence of gravity currents and topographical factors. The first scaling system was based on local values of the vertical velocity variance $\sigma _\mathrm{w}$ and the Brunt–Väisäla frequency $ N,$ while the second one was based on the temperature variance $\sigma _{\theta }$ and $N.$ Analysis showed some departures from the similarity functions (obtained for data with virtually no influence of mesoscale motions); nonetheless the overall dependency of dimensionless moments on the Richardson number was maintained.     

Summer Floods in Central Europe – Climate Change Track?

In Central Europe, river flooding has been recently recognized as a major hazard, in particular after the 1997 Odra /Oder flood, the 2001 Vistula flood, and the most destructive 2002 deluge on the Labe/Elbe. Major recent floods in central Europe are put in perspective and their common elements are identified. Having observed that flood risk and vulnerability are likely to have grown in many areas, one is curious to understand the reasons for growth. These can be sought in socio-economic domain (humans encroaching into floodplain areas), terrestrial systems (land-cover changes – urbanization, deforestation, reduction of wetlands, river regulation), and climate system. The atmospheric capacity to absorb moisture, its potential water content, and thus potential for intense precipitation, are likely to increase in a warmer climate. The changes in intense precipitation and high flows are examined, based on observations and projections. Study of projected changes in intense precipitation, using climate models, for several areas of central Europe, and in particular, for drainage basins of the upper Labe/Elbe, Odra/Oder, and Vistula is reported. Significant changes have been identified between future projections and the reference period, of relevance to flood hazard in areas, which have experienced severe recent floodings.     

Fuzzy logic circulation types based on the Osuchowska-Klein classification system created for Poland

Fuzzy logic was applied as a methodology to create an objective calendar of daily atmospheric circulation based on an existing atmospheric circulation classification system for Poland called the Osuchowska-Klein method, which includes 13 circulation patterns. In this study, circulation patterns given by Osuchowska-Klein were expressed as normalized values of sea level pressure in a regular 5°?×?5° grid over the area of interest. Cases of daily atmospheric circulation (i.e., normalized values for the same domain) observed from January 1948 to December 2007 were defined in the same manner. The pattern-matching procedure employed in the study was made objective with the application of fuzzy logic sets in a few steps as follows: (1) discrimination and grouping of grid points as well as their classification in order to clearly define each Osuchowska-Klein circulation pattern, (2) calculation of the similarity between observed normalized pressure and that of the pattern at each selected grid point using a membership function, (3) determination of the degree of fulfillment for every class of grid points, (4) determination of the degree of a case and pattern, (5) selection of the circulation type for a particular day based on the degree of fulfillment for each pattern. The largest value of the degree of fulfillment indicates the type of circulation pattern on any given day. Finally, a validation of the obtained results is discussed. This was accomplished using the chi-square test and a comparison of consistency between the traditional and objective approach types. The results do show some differences between the subjective and objective methods, however, they are not major differences, especially when taking into account the fact that the two methods are quite different, as well as the complex nature of pressure systems.