PROJECTIONS OF CLIMATE CHANGE FOR THE CZECH REPUBLIC

The paper deals with a selection of the climatological baseline, GCM validity and construction of the climate change scenarios for an impact assessment in the Czech territory. The period of 1961–1990 has been selected as the climatological baseline. The corresponding database includes more than 50 monthly mean temperature and precipitation series, and 16 time series of daily meteorological data that contain also the solar radiation data. The 1× CO₂ outputs produced by four GCMs, provided by the CSMT (GISS, GFD30, GFD01, and CCCM), were compared with observed temperature and precipitation conditions in western and central Europe with a particular attention devoted to the Czech territory. The GCM ability to simulate annual cycles of temperature, precipitation and radiation was thoroughly examined. The GISS and CCCM were selected as a basis for constructing climate change scenarios as they simulated reasonably the observed patterns. According to the GISS variant, 2× CO₂ climate assumes a higher winter and lower summer warming, and an increase in annual precipitation amounts. A dangerous combination of the summer temperature increase and declining precipitation amounts is a specific feature of the CCCM scenario. An incremental scenario for temperature and precipitation is based on the combination of prescribed changes in both annual means and annual courses.     

近30年西藏地区雷暴变化特征

利用西藏地区38个观测站点1979-2008年雷暴资料,采用旋转EOF分析、合成分析、小波分析及趋势分析等统计方法对西藏地区雷暴的时空变化规律进行了研究.结果表明:两藏地区以午后短时热力性雷暴为主,雷暴平均总次数存在准15年的周期变化,年雷暴平均总次数呈逐年减少趋势,2000年以后这种趋势更为明显.雷暴持续期变短,但也...     

豫西三门峡地区温塘断裂第四纪活动性研究

温塘断裂位于鄂尔多斯块体东南缘,是三门峡盆地的东边界控制断裂,准确厘定其活动性对于理解区域构造演化和判断三门峡地区地震危险性具有重要意义。运用野外地质地貌调查、联合钻孔剖面探测及光释光定年技术,对三门峡地区温塘断裂的活动性进行分析与研究。结果表明,温塘断裂南段出露地表,线性特征明显,断层最新活动时代为晚更新世;温塘断裂中段为第四纪隐伏断裂,断层活动时代为中更新世;温塘断裂北段断层出露,断层活动时代为中更新世。     

三峡库区奉节县宝塔坪小区大型复杂滑坡特征及成因机制

奉节县新城宝塔坪小区的地质灾害问题是当前学术界关注的焦点,也是库区具有普遍性问题。本文首次提出,在小区发育有５个复杂结构的滑坡。滑坡具３种成因：（１）碎裂－溶蚀－杏黄色泥质条带发育－滑坡;（２）碎裂－溶蚀－Ｔ２ｂ＾２粉砂质泥岩顶层泥化－滑坡;（３）Ｔ２ｂ＾４泥岩溶蚀－滑坡。岩溶蚀作用为主导作用。断裂的发育为溶蚀作用提供了通道。     

A densification mechanism to model the mechanical effect of methane hydrates in sandy sediments

Recent pore-scale observations and geomechanical investigations suggest the lack of true cohesion in methane hydrate-bearing sediments (MHBSs) and propose that their mechanical behavior is governed by kinematic constrictions at pore-scale. This paper presents a constitutive model for MHBS, which does not rely on physical bonding between hydrate crystals and sediment grains but on the densification effect that pore invasion with hydrate has on the sediment mechanical properties. The Hydrate-CASM extends the critical state model Clay and Sand Model (CASM) by implementing the subloading surface model and introducing the densification mechanism. The model suggests that the decrease of the sediment available void volume during hydrate formation stiffens its structure and has a similar mechanical effect as the increase of sediment density. In particular, the model attributes stress-strain changes observed in MHBS to the variations in sediment available void volume with hydrate saturation and its consequent effect on isotropic yield stress and swelling line slope. The model performance is examined against published experimental data from drained triaxial tests performed at different confining stress and with distinct hydrate saturation and morphology. Overall, the simulations capture the influence of hydrate saturation in both the magnitude and trend of the stiffness, shear strength, and volumetric response of synthetic MHBS. The results are validated against those obtained from previous mechanical models for MHBS that examine the same experimental data. The Hydrate-CASM performs similarly to previous models, but its formulation only requires one hydrate-related empirical parameter to express changes in the sediment elastic stiffness with hydrate saturation.     

The Cathedral of S. Giorgio in Ragusa Ibla (Italy): characterization of construction materials and their chromatic alteration

The Cathedral of St. Giorgio in Ragusa Ibla (Sicily) is one of the most important Baroque monuments of eastern Sicily. The restoration of the monument underway has put forward notable questions regarding the stone materials used and their state of degradation. The façade appears to be made mainly of a creamy white calcarenite, and of mortars and plasters. However, detailed analysis has highlighted a more complex use of the raw material. The mortar and plaster have a different composition in regards to their architectural use while the natural stone material is distinguished not only by a creamy-white calcarenite but also by a dark coloured bituminous calcarenite (pitch rock), which now appears whiter because of superficial chromatic alterations. This process was reproduced in the laboratory using an accelerated aging technique on samples of bituminous calcarenite, which allowed the cause of the alternation to be identified as photo-oxidation of the asphaltenes. Following this process of photo-oxidation, other forms of chromatic alterations affected the façade (brown–orange-coloured patinas). FTIR, Scanning Electron Microscope and thin section microscopic observation allowed the characterization of also the products of this process to be carried out, highlighting the complex mechanism which the processes underwent.     

The geomagenetic storm effect in the middle atmosphere — First results

Summary Geomagnetic storms belong to the most important phenomena of solar origin which affect the ionosphere and atmosphere. We study the responses of the lower ionosphere, middle stratospheric ozone, total ozone and the troposphere (vorticity area index at 500 hPa) to isolated and major geomagnetic storms. The expected positive effect is observed in the lower ionosphere. No observable effect is detected in the middle stratospheric ozone. An effect (not very significant) can be found in the total ozone and the troposphere.Contribution No, 109/90, Geophysical Institute, Czechosl. Acad. Sci., Prague.     

Nitric oxide density measurements at middle latitudes

Summary The measurements of nitric oxide density were made by the photoionization method at 30–90km in several rocket flights near Volgograd. TheseNO densities are well within the range of other measurements below 60km, but become rather high above 70km. The upper mesosphericNO densities estimated by two different methods from ionospheric data in Central Europe (50 °N) are rather high, as well. The appropriateNO densities in the upper mesosphere still seem to be an open question.     

Complementary Investigative Techniques for Site Assessment with Low-Level Contaminants

A remedial investigation (RI) was performed in an area downgradient from an abandoned missile silo at Vandenberg Air Force Base, California, as part of the United States Air Force Installation Restoration Program (IRP). A number of complementary investigative techniques were used to assure a reliable assessment of site contamination. These included the review of aerial photographs, the use of an organic vapor analyzer (OVA) and carbon adsorption/mass spectrometer (MS) method to conduct a soil-gas survey; magnetic and electromagnetic geophysical surveys; bedrock permeability testing; and the chemical analysis of soil, sediment, surface water, and ground water samples. The results from this investigation revealed the presence of an undocumented landfill and a small trichloroethylene plume in ground water at concentrations ranging from 6.7 ppb to 31 ppb. The investigation also identified local ground water flow direction, provided strong evidence of the location of potential sources of contamination, and defined the downgradient extent of ground water contamination. Because the identified contaminants have not as yet reached the environmentally sensitive wetland at the base of the slope below this facility, there is still time to propose remedial alternatives that would serve to protect this environmentally sensitive area.