Palaeoclimate indicators (clay minerals,calcareous nannofossils,stable isotopes) compared from two successions in the late Jurassic of the Volga Basin (SE Russia)

A study of clay mineral and calcareous nannofossil abundances in late Jurassic–early Cretaceous sediments from the Volga Basin, SE Russia, is presented. From these results, we are able to compare some general patterns of mineralogical and palaeontological change for the Volga Basin to the palaeoclimate models developed for northern Europe and beyond. The two successions examined comprise calcareous mudstones with black organic‐rich shale horizons, overlain by a series of phosphatic silty sands. Clay mineralogical results show a progressive decrease in kaolinite and the concomitant increase of smectite and illite through the middle Volgian, followed by an abrupt increase in kaolinite in the late Volgian. The clay mineral evidence suggests increasing aridity at the end of the Jurassic, similar, in part, to many western European successions. Because of differential settling of clay minerals, superimposed upon this possible climatic signature is likely to be the effect of relative sea‐level change. Calcareous nannofossil analysis from a single section reveals a shift through the middle Volgian from low nutrient, warm water assemblages dominated by Watznaueria to cooler surface water and high nutrient assemblages dominated by Biscutum constans. These observations suggest that increased aridity is also associated with climatic cooling. Black shales are associated with increased productivity, higher sea levels and increases in smectite content. Hence, periods of low (chemical) hinterland weathering during semi‐arid conditions are paradoxically associated with relatively nutrient‐rich waters, and organic‐rich shales. Comparison of published carbon and oxygen stable isotope results from this and other sections to the clay mineral and nannofossil data confirms the palaeoclimatic interpretation. This study significantly improves the published biostratigraphically constrained clay mineral database for this time period, because other European and North American successions are either non‐marine (and thus poorly dated), absent (through penecontemporaneous erosion) or condensed. Copyright © 2002 John Wiley & Sons, Ltd.     

Analysis and comparison of heat flux of landfast ice during 2016 in the Prydz Bay,Antarctica

Long term in situ atmospheric observation of the landfast ice nearby Zhongshan Station in the Prydz Bay was performed from April to November 2016. The in situ observation, including the conventional meteorological elements and turbulent flux, enabled this study to evaluate the sea ice surface energy budget process. Using in situ observations, three different reanalysis datasets from the European Centre for Medium-Range Weather Forecasts Interim Re-analysis(ERA-Interim), National Centers for Environmental Prediction Reanalysis2(NCEP R2), and Japanese 55-year Reanalysis(JRA55), and the Los Alamos sea ice model, CICE, output for surface fluxes were evaluated. The observed sensible heat flux(SH) and net longwave radiation showed seasonal variation with increasing temperature. Air temperature rose from the middle of October as the solar elevation angle increased.The ice surface lost more energy by outgoing longwave radiation as temperature increased, while the shortwave radiation showed obvious increases from the middle of October. The oceanic heat flux demonstrated seasonal variation and decreased with time, where the average values were 21 W/m~2 and 11 W/m~2, before and after August,respectively. The comparisons with in situ observations show that, SH and LE(latent heat flux) of JRA55 dataset had the smallest bias and mean absolute error(MAE), and those of NCEP R2 data show the largest differences.The ERA-Interim dataset had the highest spatial resolution, but performance was modest with bias and MAE between JRA55 and NCEP R2 compare with in situ observation. The CICE results(SH and LE) were consistent with the observed data but did not demonstrate the amplitude of inner seasonal variation. The comparison revealed better shortwave and longwave radiation stimulation based on the ERA-Interim forcing in CICE than the radiation of ERA-Interim. The average sea ice temperature decreased in June and July and increased after September,which was similar to the temperature measured by buoys, with a bias and MAE of 0.9°C and 1.0°C, respectively.     

Optical properties and surface energy flux of spring fast ice in the Arctic

Over the past decades, sea ice in the polar regions has been significantly affecting local and even hemispheric climate through a positive ice albedo feedback mechanism. The role of fast ice, as opposed to drift ice, has not been well-studied due to its relatively small coverage over the earth. In this paper, the optical properties and surface energy balance of land fast ice in spring are studied using in situ observations in Barrow, Alaska. The results show that the albedo of the fast ice varied between 0.57 and 0.85 while the transmittance increased from 1.3×10?3 to 4.1×10?3 during the observation period. Snowfall and air temperature affected the albedo and absorbance of sea ice, but the transmittance had no obvious relationship with precipitation or snow cover. Net solar shortwave radiation contributes to the surface energy balance with a positive 99.2% of the incident flux, with sensible heat flux for the remaining 0.8%. Meanwhile, the ice surface loses energy through the net longwave radiation by 18.7% of the total emission, while the latent heat flux accounts for only 0.1%. Heat conduction is also an important factor in the overall energy budget of sea ice, contributing 81.2% of the energy loss. Results of the radiative transfer model reveal that the spectral transmittance of the fast ice is determined by the thickness of snow and sea ice as well as the amount of inclusions. As major inclusions, the ice biota and particulates have a significant influence on the magnitude and distribution of the spectral transmittance. Based on the radiative transfer model, concentrations of chlorophyll and particulate in the fast ice are estimated at 5.51 mg/m2 and 95.79 g/m2, which are typical values in the spring in Barrow.     

Optimal yield level of bilinear seismic isolation devices

The yield level of an insulator is one of the important parameters which are related to responses and absorbing energy under seismic input energy in isolated structures. The purpose of this paper is to determine the optimal ratios of yield force of the isolator (Q_y) to the total weight of the structures (W). To obtain the optimal ratio, 1044 two-degree-of-freedom isolated bridge models, which have bilinear isolators, were selected. These 2-DOF isolated bridge models with superstructure isolation can consider pier flexibility and various parameters of the isolator. Two formulas for determining the optimal yield ratio are proposed and compared with the previous researches. RAE (the ratio of absorbed energy by the isolator to the total input energy) is related directly to structural responses, and Optimal Yield Ratio (OYR), defined as a yield ratio at maximum RAE, can be obtained from the relationship between RAE and Q_y/W. Here, we found that RAE is a reliable factor to evaluate OYR, and it is proportional to earthquake amplitudes under the same kinds of earthquake loadings. Using the proposed formulas, OYR is determined and the optimal yield force of the isolator can be obtained easily and reliably at a seismic isolation design stage. Copyright © 1999 John Wiley & Sons, Ltd.     

Variations in snowmelt energy and energy balance characteristics with larch forest density on Mt Iwate,Japan: observations and energy balance analyses

The variation in snowmelt energy and energy components were evaluated with respect to forest density. Surface snowmelt rates, surface evaporation from snow cover and meteorological elements were measured in the open and under sparse (411 trees/ha) and dense (1433 trees/ha) larch canopies. The surface snowmelt rate decreased as the forest density increased. Based on the observations and energy balance analyses, we concluded the following. (1) Albedo decreased while the bulk coefficient for latent heat increased with forest density. (2) The duration of snowmelt increased with forest density because the energy for nocturnal cooling of the snow cover decreased. (3) When comparing the open and forested sites, the changes in snowmelt energy with forest density were caused by sensible heat flux. However, the contribution of net radiation was highest in the forested sites. Therefore, the effects of forest cover on the snowmelt energy were different when comparing both the open and forested sites and the sparse and densely forested sites. (4) The ratio of net radiation to snowmelt energy increased with forest density; although both snowmelt energy and net radiation decreased with increased forest density, the snowmelt energy decreased more rapidly. Sensible heat also decreased as forest density increased. Both albedo and downward long‐wave radiation influenced net radiation. Copyright © 1999 John Wiley & Sons, Ltd.     

季风指数及其年际变化Ⅱ.南海夏季风分量动能强度指数及其年际变化

计算了各年南海夏季风建立前后流场的场相似度、场比幅、季风分量动能强度指数和突变度.指出按变差度最大或相似度绝对值最小及其变化最陡以及比幅最小,可客观定量地定出季风来临的预兆日期,在大多年份该日期比用天气气候学方法得到的季风来临(爆发)日期要早些,且两者有较好正相关.绝大多数年份季风建立时有环流突变发生,但也有少数年份呈调和变化或二次突变.季风分量动能强度指数能够反映各年南海夏季风建立后的强度.最后分析指出,南海850hPa夏季风的前兆日期,突变度和强度指数都有明显的年际和年代际变化.     

节能温度、供热气象指数及供热参数研究

对北京市2001～2002年采暖季的室内外气象一热力试验数据进行科学分析,求出实际条件下不同环境温度、风速、辐射等气象条件下的节能温度,提出了供热气象指数及等级划分标准,推算出总供热量、供回水温度差及通过控制回水温度而知供水温度等供热参数,并已在北京市供热作业中投入应用,为实时供热调度提供了参考依据,是节能、增效、减污的基础。     

城市热岛强度订正与供热量预报

利用公主坟自动气象站(供热区)和北京市观象台(郊区)间1997～2001年4个冬季逐月(11月～3月)逐日4次气温差值,研究了城市热岛变化特征,结合其他研究提出了北京市各供热区城市热岛强度订正原则和初步结果。对北京市2001～2002年采暖季的室内外气象-热力试验数据进行科学分析,求出不同环境温度条件下单位面积供热量模式,按此模式运行则存在较大节能空间。     

RAMS模式在山谷城市模拟性能的检验

 利用2005年冬季兰州边界层试验的观测数据,分别从边界层结构、近地面温度和风速、地表通量等几个方面检验了RAMS在山谷城市的模拟性能。RAMS模式能很好地捕捉边界层结构特征,模拟的白天混合层高度和夜间稳定边界层高度和观测值非常一致。模式能较好地模拟近地面温度和地表通量的日变化特征。对模拟偏差进行统计分析,结果显示RAMS对近地面温度和风速的模拟结果是可以接受的:近地面温度的平均偏差为-1.73 ℃,RMSE为2.16 ℃,风速的平均偏差为0.35 m·s-1,RMSE和RMSVE分别为1.61 m·s-1和3.15 m·s-1。研究表明,RAMS适合作为研究兰州山谷城市大气边界层的工具。     

TESTING OF ENERGY DISSIPATING CLADDING CONNECTIONS

Properly designed precast concrete cladding could potentially provide lateral stiffness, ductility, and energy dissipation for an overall building structure, especially during earthquakes. This paper describes a set of advanced connections that take advantage of the interaction between facade panels and structure (mainly due to horizontal interstorey drift) to dissipate energy, thereby reducing the response of the main structure. The results of an experimental program to characterize the hysteretic behaviour of advanced connections are presented. Design equations for the advanced connections are then calibrated against the test results, and the corresponding design charts are presented. It is anticipated that this research will lead to innovative ways of viewing the entire cladding system of a building.