基于概率密度分析长江三角洲降水随时间的演变规律

将长江三角洲旱涝等级资料转换成降水概率随时间的演化，揭示了长江三角洲降水概率随时间演变的各层次的分布特征。结果表明：长江三角洲降水存在明显的年际、年代际以及世纪以上时间尺度的准周期变化，而且都超过0.05的信度检验。在530年旱涝等级序列中，虽然长江三角洲各地区发生旱、涝的小概率事件的频数不太相同，但由气候态背景(世纪尺度)所激发的小概率事件频数相同；这一研究结果充分说明作为背景状态的气候演变对小概率事件（干旱、洪涝）的发生具有非常重要的影响，对气候预测理论与提高气候预测准确率具有积极的指导作用。     

中国东部2012年夏季降水及年代际转型的可能信号分析

针对2012年夏季中国东部降水"南旱北涝"的异常特征, 对比分析了近50年不同年代中国东部降水的分布型及海洋和环流等影响因素, 并讨论了2012年中国东部夏季降水异常作为中国东部降水年代际转型信号的可能性. 研究结果表明: 1961—1978年期间, 北太平洋年代际涛动(PDO)处于冷位相, 东亚夏季风偏强, 西太平洋副热带高压(副高)偏弱, 北方地区冷空气活动偏弱, 从而有利于南方水汽北上, 造成中国北方地区夏季降水异常偏多; 1979—1992年间则呈相反的特征, 造成1970年代末期中国东部夏季降水发生了一次年代际尺度的调整. 2010年代后期以来, PDO由暖位相向冷位向转变, 2012年北太平洋海温异常偏暖, 西太平洋海温由异常偏暖状态转变为正常略偏冷状态, 东亚夏季风由弱变强, 副高由强变弱, 北方冷系统活动减弱, 这些特征均与1961—1978年时段的情况类似, 支持2012年作为中国东部夏季降水发生年代际调整的前期信号的可能性. 近10年PDO, 东亚夏季风(EASM), 副高(WPSH)和贝湖高压(BH)四种指数夏季平均值的演变则进一步说明 了2012年的这种异常特征不仅是年际尺度的振荡, 更可能是前期演化基础上的一种量变到质变的调整. 关键词： 年代际 降水 北太平洋年代际涛动 东亚夏季风     

近60年新疆降水趋势与波动机制分析

用小波多尺度分析和回归等方法研究了近60年新疆降水记录的波动与趋势特征, 结果发现21世纪头十年降水亦然保持增加趋势, 但春、夏降水已呈弱的非线性下降趋势, 秋、冬季节降水增加趋势明显. 这可能与气候暖化的季节不均匀性有关. 年降水量的振荡与北大西洋涛动(NAO)关系密切, 二者约80%的方差都集中在年际尺度和多年代尺度成分两个带上, 年际变化之间呈显著负相关关系. NAO的多年代尺度成分位相超前降水10年左右, 而大西洋海温的多年代尺度涛动与之相差5年, 后者与降水的关联更为密切. "极差"分析表明, 对应于NAO的极端正或负位相事件, 下游的降水和水汽环境明显不同. 在NAO极端负位相年, 中亚和新疆降水都明显增加, 来自欧洲南部的水汽输送和中纬度瞬变涡动水汽输送均偏强, 中亚大气可降水量上升, 冷空气路径偏西, 瞬变天气系统易得到西南水汽输送带的配合, 水汽辐合增强, 有利于新疆和中亚的降水. 反之, 西风带水汽输送偏弱, 天气过程偏少, 降水量偏小, 易发生干旱. 因此, NAO的异常是新疆和中亚降水年际波动的主要原因之一. 关键词： 新疆降水 北大西洋涛动 水汽输送 瞬变涡动     

青藏高原扎布耶盐湖SZK01孔粘土矿物X射线粉晶衍射分析

青藏高原具有独特的地质地理区位优势,并且是我国最大的盐湖分布区,在其晚第四纪湖相沉积中保存着丰富多彩的古环境信息,可为研究青藏高原对全球变化的响应提供崭新而翔实的科学依据。扎布耶盐湖位于青藏高原腹地北部,对于高精度研究青藏高原更新世晚期以来古气候、古环境变化具有重要意义。选择扎布耶盐湖SZK01孔岩芯粘土矿物为主要研究对象,通过X射线粉晶衍射对其进行定性、定量分析。结果显示粘土矿物种类主要是伊利石（I）、伊利石/蒙皂石混层矿物(I/S)以及少量高岭石(K)和绿泥石(C)。按照粘土矿物种类和含量变化,并综合沉积物矿物组合特征以及δ18O同位素结果,重建扎布耶盐湖115 ka(千年)以来的古气候演化。将结果与扎布耶SZK02孔、格陵兰冰芯、古里雅冰芯δ18O同位素结果对比,将扎布耶盐湖115 ka以来划分为5个阶段：末次间冰期（115～75.5 ka）、末次冰期早阶（75.5～60 ka）、末次冰期间冰阶（60～30.1 ka）、末次盛冰期（30.1～16.7 ka）、冰消期和全新世（16.7 ka以来）,识别出H6-H16个Heinrich事件和71 ka左右的暖事件,说明青藏高原在该时期气候变化具有全球性。特别的是在52～53 ka左右,高岭石含量较低,δ18O值急剧偏负,SZK02孔δ18O也相应偏负,古里雅冰芯δ18O也偏负,说明青藏高原该时段存在冷事件,命名为H5-1。通过该研究综合说明青藏高原在末次冰期早冰阶以来气候变化具有全球性,但也有一定的地域性。     

中国冬季区域性极端低温事件分类及其与气候指数极端性的联系

基于区域性极端低温事件客观识别技术, 对1951–2010年中国冬季的区域性极端低温事件进行客观识别. 根据事件的空间分布特征, 将综合指数前60位的事件划分为全国型、东部型、东北-华北型、华北-华南型、北方型和西北-华南型六类; 通过分析不同区域类型低温事件形成的环流背景场验证了分类的有效性. 在此基础上, 以1971年1月21日开始的典型事件为例, 分析了事件对应的海温场、高度场和风场的异常, 确定与区域性极端低温事件联系较密切的可能气候因子, 进而分析不同类型事件与各气候指数异常的对应关系. 总体而言, 赤道中东太平洋海温指数异常偏小、北太平洋涛动指数异常偏小、北极涛动指数异常偏小和冬季风异常偏强时, 发生区域性极端低温事件的概率较高; 且这四种指数的历年冬季平均值达到15%(或85%)极端阈值的年份中, 发生区域性极端低温事件的百分率分别达到80.0%, 77.8%, 60.0%和62.5%, 从而为区域性极端低温事件的诊断和预测研究等提供了一定的参考. 关键词： 区域性极端低温事件 空间分类 气候指数 极端     

取代基效应(SCS)与乙烯-α-烯烃共聚物的序列结构Ⅲ.定量分析

本文在分析乙烯-α-烯烃共聚物序列结构时,把代表共单体反接单元的亚甲基(CH₂)βγ和γδ分别归属给了二元组VV和三元组EEV。与此同时,CH₂-δδ和δδ⁺归属给了二元组EE。表征乙烯长序列的CH₂-δ⁺δ⁺分属二元组EE和三元组EEE,对应峰强度在EE和EEE之间的分配是处理序列分布的关键。在本文中运用序列结构的Bovey关系和Randall统计进行演算,求得了修正值△的数学表达式,严格解和近似解。在规则链条件下得到的近似解与G.J.Ray的结果完全相同。当共单体含量较少时,谱峰强度Iδ⁺δ⁺的分配接近相等。在二元组和三元组的水平上,乙烯-α-稀烃共聚物的¹³C NMR谱中共有十三个峰,属于CH₂的有十个,属于CH的有三个。利用这些谱峰的强度数据可以建立一套计算公式,由此提供共聚物序列结构的全部信息。因此这是一个研究乙烯-α-烯烃共聚物序列结构的普适方法。     

基于复杂度分析冰芯和石笋代用资料时间序列的研究

运用动态非线性时间序列分析方法——Lemper-Ziv复杂度，分别计算了古里雅冰芯资料和北 京石花洞石笋资料的复杂度，探讨了复杂度的物理内涵及其在气候变化研究中的意义；小波 多尺度分解分析表明，复杂度序列具有明显的特征周期，存在780年、380年、160年和105年 的准周期.进一步研究发现，当取不同的窗口长度时，复杂度序列的特征基本相同；并且复 杂度序列的突变和气候突变在时间尺度上有着较好的对应关系.揭示了近千年来，在380年时 间尺度上的准周期振荡，其振幅一直是在减弱的，而且其固有周期频率逐渐减小.1900年复 杂度开始持续下降，1920年之后变化很小，类似于中国6世纪中期及12世纪中期的变暖期， 因此造成20世纪气候变暖的原因还有待于深入研究. 关键词： Lemper-Ziv复杂度 小波变换 气候 自然变率     

中国近1000年旱涝的持续性特征研究

应用中国近531年旱涝指数和近1041年干湿指数,定义干旱(湿润)等级,滑动计算原指数序列各干旱(湿润)等级的出现次数,发现各等级出现的次数与其窗口长度之间均遵循指数分布P_i(x)=Ae^-γx.结合指数分布的数理意义,定义指数特征值γ的倒数λ为描述旱(涝)持续性的尺度因子并对华北和江淮流域旱(涝)发生的持续性特征进行研究.结果表明：旱尺度因子的空间分布表现为由北向南呈带状式波动分布,我国北方地区干旱的持续性相对长江流域要长一些,由北向南三个区的旱尺度因子的均值分别为187,162,182.旱涝指数序列中旱或偏旱(涝或偏涝)相对集中的时段对旱(涝)持续性影响较显著,12世纪末期、13世纪早期、17世纪早期和20世纪末期华北和江淮流域发生时间上同步、空间上尺度较大的极端干旱事件的概率较高,这也从侧面验证了旱涝指数序列中群发现象的存在;华北地区1260—1280年(对应的气候背景为中世纪暖期的末期)的旱涝指数对旱尺度因子的影响较1980—2000年(对应的气候背景为20世纪全球增暖)的情况更显著;1260—1280年这一时段旱或偏旱年数较1980—2000年也要多一些.因此,在气候较暖的时期可能易发生强度大、范围广的同步干旱事件,而近30年的中国北方干旱化可能是自然变率起主导作用下人为变率和自然变率共同作用的结果. 关键词： 旱(涝)尺度因子 持续性 群发性 指数分布     

黄土高原中部秋季干湿的年际和年代际环流异常特征及与海温的多尺度相关性研究

黄土高原地区作为气候敏感区和生态脆弱区地表干 湿状况的年际和年代际变化特征十分明显. 但以往主要是针对夏季进行分析, 而对黄土高原秋季干湿变化规律及大气环流机理的认识非常有限. 本文基于中国589站最近50 a (1961–2010年)月降水和气温月平均资料、NCEP/NCAR提供的再分析资料以及NOAA提供的海表温度(Sea Surface Temperature, SST) 资料, 运用带通/低通滤波、小波分析、EOF/REOF和回归分析等方法, 在对中国秋季干湿时空演化分类的基础上, 通过研究秋季黄土高原中部干湿演变周期、大气环流特征及与海温的多尺度相关关系, 以揭示影响黄土高原中部秋季干湿变化的物理机理, 并确定影响该区域干湿状况的前兆信号. 小波功率谱分析表明, 黄土高原中部秋季干湿指数存在准4 a和准8 a的周期, 1970–1990年准8 a尺度周期振荡尤为明显. 年际(周期≤ 8 a) 尺度上偏湿年的大气环流特征是, 欧亚大陆中高纬呈“双阻型”, 200 hPa西风急流显著北移, 日本海-鄂霍茨克海受反气旋控制, 其底部的偏东水汽输送带将水汽输入研究区. 年代际(周期 > 8 a)尺度上偏湿年的大气环流特征是, 东亚大陆为一致的低值系统; 200 hPa东亚副热带西风急流减弱北移, 研究区主要水汽来源由经孟加拉湾在中南半岛转向的南风水汽输送及中纬度的西风水汽输送组成. 整个序列上, Nino3区SST指数(Nino3I)超前5个月与秋季干湿指数已呈显著的负相关关系, 而孟加拉湾–中国南海SST指数(BayI)则超前3个月与干湿指数呈现显著的负相关关系. 年际尺度上, 秋季Nino3I, BayI均与秋季干湿指数存在显著相关(准4 a, 4–6 a), 而年代际尺度上, 只有BayI与秋季干湿指数存在显著相关性(准10 a). 黄土高原中部秋季干湿的年际和年代际周期的确定、大气环流异常特征的认识及与海温的多尺度相关关系的建立, 不仅揭示了影响该区域干湿变化的物理机理, 也为干旱气候预测提供了重要的前兆信号. 关键词： 黄土高原中部 干湿特征 海表温度 小波分析     

一类厄尔尼诺/拉尼娜-南方涛动海-气振子的奇摄动解

厄尔尼诺/拉尼娜-南方涛动是涉及赤道太平洋中的一个海-气交互的年际现象.本文的目的是建立一类海-气振子模型的非线性奇摄动问题的渐近求解方法.并在一类海-气振子模型的基础上,借用奇摄动方法研究了对应问题的近似解.由奇摄动方法得到的结果分析厄尔尼诺/拉尼娜-南方涛动海-气振子模型的赤道太平洋的海表温度异常和气-海振子的温度深度异常.     

High-precision measurements of δ2H, δ18O and δ17O in water with the aid of cavity ring-down laser spectroscopy

A thorough evaluation of measurement uncertainty together with control of short-term and long-term precision of measurements should be a basis of any successful quality assurance/quality control (QA/QC) strategy aimed at maintaining a high quality of the analytical process. Here we present the results of a comprehensive assessment of the analytical performance of a Picarro L2140-i CRDS laser spectrometer analysing δ²H, δ¹⁸O and δ¹⁷O in water. The assessment is based on results obtained during 15 months of continuous operation of this instrument (February 2017 to May 2018). The short-term precision of measured and derived quantities was 0.11, 0.036, 0.028, 0.23 ‰ and 11 per meg, for δ²H, δ¹⁸O, δ¹⁷O, d-excess and Δ¹⁷O, respectively, and is comparable to the precision reported by the manufacturer. The long-term precision of the L2140-i, defined as standard uncertainty of the time series of 153 analyses of a laboratory standard conducted throughout 15 months, was roughly two times lower (0.24, 0.053, 0.038, 0.37 ‰ and 21 per meg, for δ²H, δ¹⁸O, δ¹⁷O, d-excess and Δ¹⁷O). In-depth assessment of the measurement uncertainty of a single analysis revealed that assigned uncertainty of the calibration standards is an important component of the uncertainty budget, especially in case of δ²H analysis.     

Defining near-surface groundwater flow regimes in the semi-arid glaciated plains of North America

The dominant transport mechanisms controlling the migration of contaminants in geologic media are advection and molecular diffusion. To date, defining which transport mechanism dominates in saturated, non-lithified sediments has been difficult. Here, we illustrate the value of using detailed profiles of the conservative stable isotope values of water (δ²H and δ¹⁸O) to identify the dominant processes of contaminant transport (i.e. diffusion- or advection-dominated transport) in near-surface, non-lithified, saturated sediments of the Interior Plains of North America (IPNA). The approach presented uses detailed δ¹⁸O analyses of glacial till, glaciolacustrine clay, and fluvial sand core samples taken to depths of 11–50 m below ground at 22 sites across the IPNA to show whether transport in the fractured and oxidized sediments is dominated by advection or diffusion. Diffusion is by far the dominant transport mechanism in fine-textured lacustrine and glacial till sediments, but lateral advection dominates transport in sand-rich sediments and some oxidized, fine-textured lacustrine and glacial till sediments. The approach presented has a number of applications, including identifying dominant transport mechanisms in geomedia and potential protective barriers for underlying aquifers or surface waters, constraining groundwater transport models, and selecting optimum locations for monitoring wells. These findings should be applicable to most glaciated regions of the world that are composed of similar hydrogeologic units (i.e. low K clay till layers overlain by higher K coarse-textured aquifers or weathered clay till layers) and may also be applicable to non-glaciated regions exhibiting similar hydrogeologic characteristics.     

Delineating sources of groundwater recharge and carbon in Holocene aquifers of the central Gangetic basin using stable isotopic signatures

Stable isotopes of water (δ²H, δ¹⁸O) and δ¹³C_TIC were used as a tool to trace the recharge processes, natural carbon (organic and inorganic) source and dynamics in the aquifers of the central Gangetic basin, India. Stable isotope (δ²H, δ¹⁸O) record of groundwater (n?=?105) revealed that the groundwater of Piedmont was recharged by meteoric origin before evaporation, while aquifers of the older and younger alluvium were recharged by water that had undergone evaporation loss. River Ganges and its tributaries passing through this area have very little contribution in recharging while ponds play no role in the recharging of adjacent aquifers. The connectivity of shallow aquifers of aquitard formation (comprised of clay/sandy clay with thin patches of fine grey sand), i.e. 25–60?m below ground level (bgl) with the main upper aquifer (at a depth of >120?m?bgl) was found to be higher in older and younger alluvium. Negative values of δ¹³C_TIC (median ?9.6 ‰; range ?13.2 to ?5.4 ‰) and high TIC (median 35?mM; range 31–46?mM) coupled with low TOC (median 1.35?mg/L; range 0.99–1.77?mg/L) indicated acceleration in microbial activity in the younger alluvium, especially in the active floodplain of river Ganges and its proximity.     

Spatial and temporal variation of H and O isotopic compositions of the Xijiang River system,Southwest China

Ratios of stable isotopes of hydrogen and oxygen (²H/¹H and ¹⁸O/¹⁶O) in river waters were measured to investigate the hydrological pathway of the Xijiang River, Southwest China. The δ²H and δ¹⁸O values of river waters exhibit significant spatial and temporal variations and the isotopic compositions vary with elevation, temperature and precipitation of the recharge area. Spatially, δ¹⁸O values of river waters from high mountain areas are lower than those from the lower reaches of the Xijiang River due to lower temperature and higher elevation for the recharge area. However, both ²H and ¹⁸O are enriched differently in river waters from the middle reaches during the high flow season, depending on the season and degree of anthropogenic disturbances (e.g. water impoundments). In contrast, deuterium excess (d-excess) values of waters from the middle reaches are substantially lower than those from the upper and lower reaches, suggesting that river waters may be resided in the reservoir and evaporation increases in the middle reaches of the Xijiang River.     

Comparison of δ13C and δ18O from cellulose,whole wood,and resin-free whole wood from an old high elevation Pinus uncinata in the Spanish central Pyrenees*

δ¹³C and δ¹⁸O values from sapwood of a single Pinus uncinata tree, from a high elevation site in the Spanish Pyrenees, were determined to evaluate the differences between whole wood and resin-free whole wood. This issue is addressed for the first time with P. uncinata over a 38-year long period. Results are also compared with published isotope values of α-cellulose samples from the same tree. The differences in δ¹³C and δ¹⁸O between whole wood and resin-free whole wood vary within the analytical uncertainty of 0.3 and 0.5?‰, respectively, indicating that resin extraction is not necessary for sapwood of P. uncinata. Mean differences between cellulose and whole wood are 0.9?‰ (δ¹³C) and 5.0?‰ (δ¹⁸O), respectively. However, further analyses of different species and other sites are needed to evaluate whether the findings reported here are coherent more generally.     

Spatial variability of 2H and 18O composition of meteoric freshwater lakes in Scotland

Coastal regions, and in particular islands where precipitation from clouds formed out at sea occurs for the first time, are prime candidates for regions where ²H and ¹⁸O composition of precipitation will deviate significantly from the global mean geographic and physiographic trends of vapour-transport patterns. The results reported here are the outcome of a study that aimed to test this hypothesis by ‘isotopographically’ mapping the characteristic δ²H and δ¹⁸O signatures of Scottish freshwaters. The resulting isotope abundance landscapes or ‘isoscapes’ will underpin studies aiming to authenticate origin of Scottish produce but may also offer a baseline against which environmental changes could be assessed. Between April 2011 and May 2012 freshwater samples were collected from 127 different freshwater lochs and reservoirs across Scotland, and analysis results were compared to precipitation data provided by the British Geological Survey. Here we present the results of the ²H and ¹⁸O analyses of these water samples as well as the first detailed Scotland freshwater isoscapes with a grid resolution of about 5 × 5 km (0.05 degrees).     

USGS48 Puerto Rico precipitation – a new isotopic reference material for δ2H and δ18O measurements of water

A new secondary isotopic reference material has been prepared from Puerto Rico precipitation, which was filtered, homogenised, loaded into glass ampoules, sealed with a torch, autoclaved to eliminate biological activity, and calibrated by dual-inlet isotope-ratio mass spectrometry. This isotopic reference material, designated as USGS48, is intended to be one of two isotopic reference waters for daily normalisation of stable hydrogen (δ²H) and stable oxygen (δ¹⁸O) isotopic analysis of water with a mass spectrometer or a laser absorption spectrometer. The δ²H and δ¹⁸O values of this reference water are?2.0±0.4 and?2.224±0.012 ‰, respectively, relative to Vienna Standard Mean Ocean Water on scales normalised such that the δ²H and δ¹⁸O values of Standard Light Antarctic Precipitation reference water are?428 and?55.5 ‰, respectively. Each uncertainty is an estimated expanded uncertainty (U=2u_c) about the reference value that provides an interval that has about a 95 % probability of encompassing the true value. This isotopic reference water is available by the case of 144 glass ampoules containing 5 mL of water in each ampoule.     

Hydrogeological responses in tropical mountainous springs

This study presents a hydrogeochemical analysis of spring responses (2013–2017) in the tropical mountainous region of the Central Valley of Costa Rica. The isotopic distribution of δ¹⁸O and δ²H in rainfall resulted in a highly significant meteoric water line: δ²H?=?7.93·δ¹⁸O?+?10.37 (r^2? =?0.97). Rainfall isotopic composition exhibited a strong amount-dependent seasonality. The isotopic variation (δ¹⁸O) of two springs within the Barva aquifer was simulated using the FlowPC program to determine mean transit times (MTTs). Exponential-piston and dispersion distribution functions provided the best-fit to the observed isotopic composition at Flores and Sacramento springs, respectively. MTTs corresponded to 1.23?±?0.03 (Sacramento) and 1.42?±?0.04 (Flores) years. The greater MTT was represented by a homogeneous geochemical composition at Flores, whereas the smaller MTT at Sacramento is reflected in a more variable geochemical response. The results may be used to enhance modelling efforts in central Costa Rica, whereby scarcity of long-term data limits water resources management plans.