黄河源区气候变化的季节特征与区域差异研究

基于黄河源区有关气象台站的观测数据,对该区黄河沿水文站以上、黄河沿水文站-吉迈水文站区间、吉迈水文站-玛曲水文站区间、玛曲水文站-唐乃亥水文站区间各区域及整个黄河源区1960-2014年期间气温、降水的季节变化特征及其区域差异进行了分析。结果表明：黄河源区气温变化与全球气温变化有着较好的一致性,各区年平均气温与各季气温的年际变化均呈波动状上升态势并明显高于过去50a全球与我国气温的升幅,且各气温系列升幅差异不大;而各区年平均气温与各季气温的年代际变化的上升态势较年际变化的更为显著,但不同区域各季气温升幅差异较大。各区气温均在1996年后出现一个跃动,跃动后各气温系列均值较跃动前有较大幅度的上升。由于区域地理环境的影响,黄河源区降水量的变化比较复杂,各区各季降水量的变化具有较大的差异。近50余年来,总体上整个河源区平均降水量的年际变化呈不明显的增长态势。其中河源区的上半部分,即黄河沿以上、黄河沿-吉迈之间等海拔较高的区域年降水量增长比较显著,而源区的下半部分,即吉迈-玛曲、玛曲-唐乃亥之间的区域,年降水呈减少态势,并且对全区平均降水量与产流量贡献最大的吉迈-玛曲之间的区域,年降水量的减少非常显著。各区冬春季和夏季降水量普遍呈增长态势,秋季是河源区各季节中降水唯一减少的季节,其中吉迈-玛曲之间的区间秋季降水量的减少最为显著。各区域各季降水量的年代际变化较其年际变化差异更大,但近十余年来大部分区域各季降水普遍偏多。各区域降水系列亦有突变发生,但突变时间并不像气温系列那样一致;年降水量与夏季降水量的突变大都发生在2005年,秋季降水量突变大都发生在1986年,春季和冬季降水量突变的时间杂乱无序;突变前后系列均值有增有减,且幅度大小不等。     

天山南、北坡典型河流出山径流对气候变化响应的分析对比

基于有关水文、气象台站的降水、气温和径流观测资料,对天山南、北坡的代表性河流——开都河与乌鲁木齐河上游山区径流变化及其对气候变化的响应进行了分析。在此基础上建立山区径流对气候变化的响应模型,假定不同的气候情景组合,就两条河流出山径流对气候变化的敏感性进行分析对比。结果表明,近40余年,两条河流山区年降水量、平均气温及径流总体上均呈波动状上升态势。一方面径流与降水、气温的变化呈明显的正相关关系;另一方面山区径流对降水、气温变化的响应的程度存在着明显的区域性差异,即乌鲁木齐河出山径流对降水变化的响应程度明显强于开都河,而开都河出山径流对气温变化的敏感性要高于乌鲁木齐河。     

Linking pollution induced community tolerance (PICT) and microbial community structure in chronically metal polluted estuarine sediments

We tested the ability of pollution induced community tolerance (PICT) to detect the effects of chronic metal pollution on estuarine sediment microbial communities, along a gradient spanning two orders of magnitude in metal concentrations. In tandem, we investigated the associated microbial community structure using terminal restriction fragment length polymorphism (T-RFLP). Tolerance of microbes to Cu, measured as IC50 (inhibitory concentration 50%), was strongly correlated with pore water Cu concentration (r(2)=0.842). No strong correlation existed for other metals tested, highlighting the ability of PICT to identify the pollutant causing a toxic effect. There was no correlation between microbial community structure and community tolerance to metals tested, but analysis of community structure did provide some information on reasons for observed PICT response. PICT methodology used here provided a greater strength and consistency of association with pollutant concentration compared to microbial community structure and can be recommended as a sensitive indicator of metal pollution on estuarine sediment microbial communities.     

Non-linear bending waves in Keplerian accretion discs

The non-linear dynamics of a warped accretion disc is investigated in the important case of a thin Keplerian disc with negligible viscosity and self-gravity. A one-dimensional evolutionary equation is formally derived that describes the primary non-linear and dispersive effects on propagating bending waves other than parametric instabilities. It has the form of a derivative non-linear Schrödinger (DNLS) equation with coefficients that are obtained explicitly for a particular model of a disc. The properties of this equation are analysed in some detail and illustrative numerical solutions are presented. The non-linear and dispersive effects both depend on the compressibility of the gas through its adiabatic index Γ. In the physically realistic case Γ < 3, non-linearity does not lead to the steepening of bending waves but instead enhances their linear dispersion. In the opposite case Γ > 3, non-linearity leads to wave steepening and solitary waves are supported. The effects of a small effective viscosity, which may suppress parametric instabilities, are also considered. This analysis may provide a useful point of comparison between theory and numerical simulations of warped accretion discs.     

Toxicity assessment of New Zealand and Pacific dinoflagellates Ostreopsis and Gambierdiscus (Dinophyceae) extracts using bioassays

The dinoflagellate genus Ostreopsis produces palytoxin-like compounds (PLTXs) and the genus Gambierdiscus produces ciguatoxins (CTXs) and maitotoxin (MTX). Human illness has been recorded following the consumption of CTX-contaminated finfish. Their effects on the flora and fauna in the environment are largely unexplored. Toxin profiles of extracts of Ostreopsis and Gambierdiscus isolates from the Pacific region were characterised using liquid chromatography tandem mass spectrometry. Sea urchin (Evechinus chloriticus) fertilisation was unaffected by any algal extracts, but extracts containing maitotoxin-3 (MTX-3, but not MTX or CTXs), or with high concentrations of PLTXs, were toxic to urchin larval development. Gambierdiscus extracts containing CTXs elicited toxic responses in zebrafish (Danio rerio) embryo toxicity assays; extracts containing only MTX-3 elicited a limited response. Ostreopsis extracts containing PLTXs caused no response. The results demonstrate potential impacts of toxic dinoflagellates on larval organisms and the potential of embryonic assays as toxicity screening tools.     

Effect of Electron Pressure on the Grad–Shafranov Reconstruction of Interplanetary Coronal Mass Ejections

We investigate the effect of electron pressure on the Grad–Shafranov (GS) reconstruction of Interplanetary Coronal Mass Ejection (ICME) structures. The GS method uses in situ magnetic field and plasma measurements to solve for a magnetohydrostatic quasi-equilibrium state of space plasmas. For some events, a magnetic flux-rope structure embedded within the ICME can be reconstructed. The electron temperature contributes directly to the calculation of the total plasma pressure, and in ICMEs its contribution often substantially exceeds that of proton temperature. We selected ICME events observed with the Wind spacecraft at 1 AU and applied the GS reconstruction method to each event for cases with and without electron temperature measurements. We sorted them according to the proton plasma β (the ratio of proton plasma pressure to magnetic pressure) and the electron-to-proton temperature ratio. We present case studies of three representative events, show the cross sections of GS reconstructed flux-rope structure, and discuss the electron pressure contribution to key quantities in the numerical reconstruction procedure. We summarize and compare the geometrical and physical parameters derived from the GS reconstruction results for cases with and without electron temperature contribution. We conclude that overall the electron pressure effect on the GS reconstruction results contributes to a 10?–?20 % discrepancy in some key physical quantities, such as the magnetic flux content of the ICME flux rope observed at 1 AU.     

Historical climatology, <Emphasis Type="Italic">Climatic Change</Emphasis>, and implications for climate science in the twenty-first century

Historical climatology is the use of documentary evidence for the reconstruction of past climate. This paper gives a brief personal view of the development of the discipline from early times to the present day. Although several papers have been published on the importance of carefully analysing and evaluating all historical sources before they are used in climate reconstructions, several of them in Climatic Change, the use of unreliable, unanalysed data still persists. This may lead to false impressions of the climate of the past. In these times, when climate data are being used for political, as well as purely scientific ends, the cause of accuracy, as championed by Climatic Change, will best be served by emphasising, yet again, the importance of using only reliable data. A number of examples are given which illustrate these points. These include discussions on wine growing in England in medieval times, the Norse settlement of Greenland, and comments on the climate history of the past thousand years.     

POINTE AUTOMATIQUE*

The automatic picking of seismic sections replaces the slow and painstaking task of manual reflection plotting with rapid and economical processing by computer. Essentially, reflection picking is a decision-making problem which also can be considered as a sort of filtering. Mathematically this means multiplying the seismic data matrix by a more or less complex decision operator. For the sake of economy, we give an initial solution for simple cases which only require easily automatized decision-making criteria. We describe another more elaborate method for use in examining seismic phenomena which are more difficult to spot. The process used is based on the recognition of shapes and consists first of all of determining a series of characteristics capable of identifying each reflection on each trace and then of comparing these different characteristics from trace to trace so as to be able to judge the continuity or discontinuity of the reflections. Automatic picking thus leads to a schematic time-section in which only the horizons found by calculation are retained. An automatic migration program then transforms this time-section into a depth-section.     

Deposits and physical properties of pyroclastic density currents during complex Subplinian eruptions: the AD 472 (Pollena) eruption of Somma-Vesuvius, Italy

Small-scale pyroclastic density currents (PDCs) associated with the AD 472 (Pollena) eruption of Somma-Vesuvius, Italy, were generated by both magmatic and phreatomagmatic explosive fragmentation. The resulting deposits were emplaced under flow boundary conditions dominated by varying combinations of grain interaction, fluid escape and traction processes. Stratigraphic and lithofacies analysis of these PDCs offers a new perspective on the en masse versus progressive aggradation debate for PDC deposition. In particular, the analyses indicate that PDCs were density stratified with a basal underflow dominated by grain interactions. The underflows comprised trains of self-organized granular pulses of variable thickness and magnitude, depending on the overall particle concentration and fluid turbulence. A change in gradient between the upper and lower slopes of the volcano promoted deposition and the different pulses aggraded sequentially (stepwise). In this model each pulse stops en masse and the whole deposit aggrades progressively. Particle concentration, density, mean velocity, and flow height were assessed for the studied PDCs using differaent methods for massive and stratified deposits. The calculated mobility of the flows was 0·2 to 0·3, in the expected range for small-scale PDCs.     

Rapport (1966–1976) sun les Eléments en Traces Dans Trois Roches Standards Géochimiques Du CRPG . Basalte BR et Granites, GA et GH

Cinquième de la serie des rapports d'étude coopérative sur les standards géochimiques du CRPG, ce rapport est consacré exclusivement aux éeléments en traces dans trois éahantillons en circulation depuis 1963: les Granites GA et GH et le Basalte BR. La pré-sentation de plus de 2000 données analytiques réporties sur 50 éléments est accompagnée d'une évaluation statistique et critique, échantillon par éahmtillon et élément par élément. La discussion est menée dans le sens d'un dialogue direct avec I'utilisateur en nuançant et en hiérarchieant les valeurs que nous veoamnandons ou proposons. Quant à I'analyste practician, il trouvera une table des valeurs "utilisables" pour une trentaine d'éléments dans les trois échantillons de référence (Table 4). Rappelons que ces échantillons sont déjà bien caractérises en ce qui concerne leurs constituants majeurs et mineurs, grâce aux quatre rapports d'étude coopérative dont le dernier est paru en 1370.