古气候演化特征、驱动与反馈及对现代气候变化研究的启示意义

古气候与现代气候变化研究如何有效结合,特别是古气候研究如何为理解现代气候变化过程提供背景条件、边界约束和理论框架,值得深入探讨。文章以现代、历史时期、全新世、晚第四纪和新生代为时间基线,回顾阐述了过去气候演变特征、成因机制及其对现代气候变化研究的启示意义,探讨了过去与现代气候变化融合研究中存在的不确定性。过去气候演化过程的研究,加深了人们对地球气候系统运行机制的理解。研究表明,各个时期中,地球气候经历了不同相位、幅度和速率的变化,气候系统各分量之间发生了复杂的相互作用,以地表温度为代表的地球表面热力环境演化是各不同阶段气候变化的基本表现形式。全球温度变化不仅受到太阳输出辐射、地球轨道参数和地球构造运动等的影响,而且与地球表层水圈中的海洋、冰冻圈中的大陆冰盖、生物圈中的海洋浮游生物和陆地植被,以及大气圈中的温室气体、粉尘气溶胶、水汽和云等活跃组分之间,存在着多尺度复杂反馈作用。在同一时间尺度上,气候系统分量的互馈通路可能是同向的、可比的,各分量之间的对应关系或具有一致性,研究结论对于预估未来气候变化有借鉴意义;但在不同时间尺度上,气候系统各分量之间的相互联系机制可能难有一致性和可比性,古今互鉴,就需要慎重。

     

求解GM(1,1)模型新总体最小二乘算法

在GM(1,1)模型中系数矩阵和观测向量都是由原始序列组成的。系数矩阵中同样是有误差的,与观测向量中的误差一样,亦来源于原始序列,即它们误差同源。不同位置的相同元素应该有相同的改正数,采用传统总体最小二乘求解则不能达到此目的。针对这一缺陷,推导了一种新的总体最小二乘算法;并且通过算例验证了新方法的可行性和有效性。     

Flexible membranes anchored to the ground for slope stabilisation: Numerical modelling of soil slopes using SPH

An alternative modelling for flexible membranes anchored to the ground for soil slope stabilisation is presented using Smoothed-Particle Hydrodynamics to model the unstable ground mass in a soil slope, employing a dynamic solve engine. A regression model of pressure normal to the ground, q_sim, and also membrane deflection, f_sim, have been developed using Design of Experiment. Finally, a comparison between the pressure obtained from numerical simulation and from a limit equilibrium analysis considering infinite slope has been carried out, showing differences in the results, mainly due to the membrane stiffness.     

Dynamic responses of atmospheric carbon dioxide concentration to global temperature changes between 1850 and 2010

Changes in Earth's temperature have significant impacts on the global carbon cycle that vary at different time scales, yet to quantify such impacts with a simple scheme is traditionally deemed difficult. Here, we show that, by incorporating a temperature sensitivity parameter(1.64 ppm yr~(-1) ?C~(-1)) into a simple linear carbon-cycle model, we can accurately characterize the dynamic responses of atmospheric carbon dioxide(CO_2) concentration to anthropogenic carbon emissions and global temperature changes between 1850 and 2010(r~2 0.96 and the root-mean-square error 1 ppm for the period from 1960onward). Analytical analysis also indicates that the multiplication of the parameter with the response time of the atmospheric carbon reservoir(～12 year) approximates the long-term temperature sensitivity of global atmospheric CO_2concentration(～15 ppm?C~(-1)), generally consistent with previous estimates based on reconstructed CO_2 and climate records over the Little Ice Age. Our results suggest that recent increases in global surface temperatures, which accelerate the release of carbon from the surface reservoirs into the atmosphere, have partially offset surface carbon uptakes enhanced by the elevated atmospheric CO_2 concentration and slowed the net rate of atmospheric CO_2 sequestration by global land and oceans by ～30%since the 1960 s. The linear modeling framework outlined in this paper thus provides a useful tool to diagnose the observed atmospheric CO_2 dynamics and monitor their future changes.     

江苏一次锢囚状MCS和相关中涡旋MCV的观测分析

利用常规地面和高空气象观测资料,结合气象卫星云图和雷达回波,分析了2009年6月14日15—23时(北京时,下同),造成江苏强对流天气的一个中尺度对流系统(MCS)的锢囚状特征的形成过程及其垂直结构。地面中尺度分析表明,雷暴高压东侧在飑前倒槽北端发展的闭合低压环流的东南气流将暖湿空气输送到冷性雷暴高压的北侧形成东南一西北向的暖舌,从而形成锢囚状的结构。长三角探空网资料的垂直结构分析表明,在对流层下部地面到850 hPa为冷性的雷暴高压,在对流层中部700 hPa为冷性的α中尺度涡旋(MCV),而500 hPa已转变为暖性的MCV。静力学关系可以说明MCV仅仅存在于700~500 hPa的原因和MCS下冷上暖的热力结构密切相关。     

太原市地表热环境时空格局分析

针对鲜有资源型城市的地表热环境研究这一情况,该文基于Landsat8遥感数据,反演了太原市在2013—2015年间共3期的地表温度。提出一个考虑空间格局结构的城市热岛效应指数,在3期数据中,太原市区整体热岛效应指数分别为9.1%、9.8%和8.9%;同时,根据城市功能和路网结构将太原市区划分为6个分区,从分区级层面量化分析了地表热环境的时空分异特征规律,结果表明,太原市区地表温度整体呈现空间分散化特征,不同分区也呈现出不同的时空格局演变过程;最后,选取40个地表温度实测样本点验证反演精度,最大误差绝对值为1.1℃,最小误差绝对值为0.2℃,均方根误差为0.7℃。     

时变参数灰色模型背景值重构及实现

针对时变参数灰色模型PGM(1,1)的背景值重构收敛速度及稳定性问题,该文运用积分的方法综合序列在Δt内不同变化趋势,导出背景值模型的准确表达式。实现了反映序列对新老信息偏爱程度的最优权值介于(0,1)内,且非不能越过某一阈值;给出了背景值重构模型最优解准确求取的具体算法步骤。基于MATLAB语言的实验结果表明:改进模型预测精度高,易于实现;所研究的带权灰色模型GM(1,n)背景值模型的重构及计算方法验证了PGM(1,1)模型重构及计算实现方法的有效性和实用性。     

Water-rock-tailings interactions and sources of sulfur and metals in the subtropical mining region of Taxco,Guerrero (southern Mexico): A multi-isotopic approach

Multi-isotope (H, O, S, Sr, Pb) systems coupled with conventional (major and trace element) hydrogeochemical analysis were applied to determine the origin of water, to model water-rock-tailings interactions and for source apportionment of sulfur and associated toxic metals in the mining region of Taxco, Guerrero in southern Mexico. Oxygen and H isotopes indicate that meteoric water in the zone is rainwater undergoing varying degrees of isotopic fractionation by atmospheric evaporation whereas Sr isotopes trace the interaction of pristine water from volcanics of the regional recharge zone and subsequently flowing through sandstone and shale to spring points. Leachates form from two distinctive sources (spring water and surface water) having differential interactions with bedrocks prior to entering the tailings. Compared to pristine water, leachates are enriched in sulfate, metals (e.g. Fe, Mn, Pb and Zn) and metalloids (e.g. As). The sulfur isotopic composition of ore-sulfides, leachates, secondary precipitates, regional surface water and hypogenic sulfates is described in terms of a two-component mixing model with shale of Mexcala and limestone of Morelos formations representing the light and heavy end-members, respectively, whereas Sr isotopic composition is bracketed combining three lithogenic (Mexcala/Morelos, Tilzapotla and Taxco Schist) sources. Finally, leachates have a mixture of lead from ore-sulfides and Taxco Schist Formation (Family I) or from ore-sulfides alone (Family II). The application of multiple environmental isotopic techniques is an outstanding tool for elucidating complex interactions of water with bedrocks and tailings and for determining the source of sulfur and toxic metal from mining and other metal polluted environments.     

CO2加富对塔玛亚历山大藻叶绿素荧光参数及产毒的影响

由大气中CO_2浓度升高引起的海洋酸化,是全球性的重大环境问题之一。本研究采用实验生态学的方法,以塔玛亚历山大藻(Alexandrium tamarense)为研究对象,分析其在CO_2加富条件下叶绿素荧光动力学参数及产毒特征的变化。调制叶绿素荧光结果显示,CO_2加富对塔玛亚历山大藻的PSⅡ最大光化学量子产量(Fv/Fm)、最大相对电子传递效率(r ETRmax)有显著影响(P0.05),且随着培养时间的增长Fv/Fm、r ETRmax均降低,对半饱和光强(Ik)、快速光曲线初始斜率(α)却无显著影响(P0.05)。结果说明CO_2加富能促进塔玛亚历山大藻的PSⅡ最大光化学量子产量,提高其最大光能转换效率和相对最大电子传递效率。高效液相色谱法分析结果显示,该株塔玛亚历山大藻主要产漆沟藻毒素1(GTX1)、漆沟藻毒素4(GTX4)、N-磺酰氨甲酰基毒素(C1)及N-磺酰氨甲酰基毒素(C2)四种PSTs毒素,CO_2加富不改变主要麻痹性贝毒(PSTs)的种类组成,但能显著提高氨基甲酸酯类毒素(GTX1、GTX4)产量(P0.05),而降低N-磺酰氨甲酰基类毒素(C1、C2)产量(P0.05),说明加富能使塔玛亚历山大藻所产毒素发生转化,进而影响藻细胞的整体毒性。     

Investigation of a longfin inshore squid's swimming characteristics and an underwater locomotion during acceleration

In the present study, locomotion of a real longfin inshore squid (Doryteuthis pealeii) was numerically investigated. Geometry of a real squid was obtained using computed tomography (CT) images. In addition to a two-dimensional axisymmetric squid model, a modified squid model with no cavities around her head and an ellipse shaped model were generated with a fineness ratio (the ratio of body length to maximum body diameter) of 7.56. These numerical models were exposed to an acceleration with two different velocity programs. Added mass and basset forces on bodies were calculated during acceleration of the squid models starting from rest. Pressure and viscous drag forces were also calculated due to pressure variation along the squid models and friction on the surface of the models. The effect of a nozzle diameter on jet velocities and propulsive efficiency at all bodies were evaluated when time dependent velocity profiles (from 0 to 10 m/s in 0.5 and 1 s time durations) were set for the inlet of computational domain. The modified squid model required least thrust force during acceleration phase of time dependent velocity profile compared to the other models while the 0.02 m nozzle diameter provided largest propulsive efficiency for all models.