The past climate and sea-ice record from Iceland,Part 1: Data to A.D. 1780

A new reconstruction of the climate and sea-ice record for Iceland from medieval times to A.D. 1780 is presented, based on all available documentary sources. The importance of careful historical analysis to separate reliable from unreliable material is stressed, and these reconstructions are the first to have been produced using only reliable data. The major previous works on the subject (those of Thoroddsen, Koch, and Bergþórsson), which all include unreliable material, are discussed. Prior to A.D. 1600 the data are not considered to be full enough to permit a quantitative interpretation. For the period A.D. 1601 to 1780 decadal temperature and sea-ice indices are given.Although there is very little evidence for the first few centuries of settlement in Iceland (from c. 870 to c. 1170) the data suggest a fairly mild climatic period. Cold periods occurred around 1200, and at the end of the thirteenth century. The fourteenth century was very variable with a cold period in the 1350s to c. 1380. Between 1430 and c. 1560 there are very few contemporary sources and it is difficult to draw any conclusions on the climate during this time. The latter part of the sixteenth century was undoubtedly cold. From 1601 there are sufficient data to permit a decade by decade analysis. This shows a mild period between 1640 and 1670, and severe decades in the 1630s, 1690s, 1740s, and 1750s. Year to year and decade to decade variability is appreciable. The correlation between temperature and sea ice is not perfect but is still quite strong (similar to today). Because data have been gathered from different regions of Iceland it has been possible to demonstrate the spatial variability of Iceland's climate during the period 1601 to 1780. For example, during 1660 to 1700 there was a cooling in the north and west but warming in the south. The 1690s, the coldest decade of the Little Ice Age in Europe, was extremely cold in the west of Iceland, but less severe elsewhere.

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Helium abundance in the solar wind

Observations of hydrogen and helium ions in the solar wind have been carried out by the Goddard Space Flight Center - University of Maryland plasma instrument on Explorer 34. These ions are completely separated by means of electrostatic and magnetic fields. The average value of the ratio of number densities is 0.051 ± .02, derived from over 3000 h of measurement. Variations about this value from about 0.01 up to greater than 0.15 occur, and there are more high values than can be explained by random variation. A tentative association with some geomagnetic storms is suggested. The above value of abundance, assuming that plasma emitted in the ecliptic plane is a fair sample of the output of the sun, combined with other recent work by other methods indicate that the solar abundance may be about half the previously quoted estimates of approximately 0.1.     

动力降尺度CMIP5的2006—2035新疆夏季降水变化

评估了CMIP5 9个模式对新疆夏季降水的模拟效果,从中选取5个较好的模式结果,利用RegCM4动力降尺度再集合平均。通过对CMIP5 9个模式的评估,发现CanCM4、CMCC-CM、CNRM-CM5、HadCM3、MIROC4h对新疆夏季降水的模拟较好。进一步分析动力降尺度和集合平均结果,发现动力降尺度能更好地描述新疆复杂地形造成的降水,同时发现2006—2035年比1976—2005年新疆夏季的总体降水有所减少,存在明显的减少趋势。在空间分布上主要表现为天山山脉和其南侧降水显著减少,昆仑山山脉北缘降水显著增加,这与2006—2035年新疆东北侧500 hPa出现的位势高度正异常和与之相对应的反气旋式环流异常有关。这一环流异常造成了天山山脉上空水汽的显著辐散和昆仑山山脉北缘上空水汽的显著辐合。     

1961-2014年黄河源区蒸发皿蒸发量变化的多尺度特征及突变分析

基于黄河源区相关气象站1961-2014年蒸发皿蒸发数据,利用线性倾向分析、滑动平均法、Mann-Kendall法等方法,对黄河源区各分区及整个源区蒸发皿蒸发量变化进行多尺度变化特征及突变分析。结果表明：近50余年来,空间上,黄河源区年平均蒸发量经历了从上游到下游先减小后增加的过程,季节蒸发量变化稍有差异;时间上,黄河源区季节及年平均蒸发量总体呈上升趋势,各分区略有差异,各分区及整个源区蒸发量年代际变化具有较好的一致性。各分区及整个黄河源区年平均及季节平均蒸发量突变点基本一致,均出现在2000年前后,且年与季节平均蒸发量在突变前均值大部分小于突变后的均值。位于源区下游的玛曲-兴海平均蒸发量发生突变的时间较早,且跳跃幅度较小,位于源区中游的达日-玛曲平均蒸发量发生突变的时间较晚,且跳跃幅度较大。对各气象因子的相关分析表明,影响源区年蒸发量变化的主要因子为平均温度。     

3种土壤冻融判别算法在青藏高原的分类精度评价

本文比较了基于AMSR-E被动微波数据的3种土壤冻融判别算法在青藏高原相关地区的分类精度。3种算法分别是：双指标算法、决策树算法、判别函数算法。本文选取了来自青藏高原那曲、玛曲、阿里3个地区土壤温湿度观测网的地表温度数据,并结合AMSR-E被动亮温数据,对上述算法在以上地区的分类精度分别进行了比较评价。结果表明：不论是白天还是夜间,相较于干旱区微波信号来自深层土壤的难以准确探测,在青藏高原半湿润半干旱区算法可取得相对较好的判别准确率;双指标算法相较于其他2种算法,在观测区具有较高的分类精度,且夜间分类精度高于白天;实测数据存在资料代表性不普遍即网格所包含站点信息量不够的问题,这也是后续工作中提高分类精度值得关注的着手点。     

拉萨近45年浅层地温的变化特征

利用1961-2005年拉萨0～40cm各层逐月平均地温,采用气候倾向率、累积距平、信噪比等气候统计方法,研究了近45年拉萨浅层平均地温的变化趋势、气候突变和异常年份等。结果表明:浅层各季节平均地温均呈现为极显著的升高趋势,升温率为0.43～0.60℃/10a,春季最大、夏季最小。各层年平均地温以0.45～0.66℃/10a的升温率显著上升,40cm深度的升温率最大,与同时期平均气温的升温率比较,地温比气温对气候变暖的响应更强。20世纪60年代至90年代浅层年、季平均地温呈明显的逐年代升高趋势,以冬、春季最为明显。60年代到80年代中期为偏冷阶段,80年代后期至90年代地温为偏暖阶段。各浅层平均地温在1986年秋季均发生了突变,冬季突变时间都出现在1984年。年平均地温除在40cm处1999年异常偏高外,其它各层为异常偏低年份,且发生在20世纪60年代。     

A review of volatile compounds in tektites,and carbon content and isotopic composition of moldavite glass

Abstract– Tektites, natural silica‐rich glasses produced during impact events, commonly contain bubbles. The paper reviews published data on pressure and composition of a gas phase contained in the tektite bubbles and data on other volatile compounds which can be released from tektites by either high‐temperature melting or by crushing or milling under vacuum. Gas extraction from tektites using high‐temperature melting generally produced higher gas yield and different gas composition than the low‐temperature extraction using crushing or milling under vacuum. The high‐temperature extraction obviously releases volatiles not only from the bubbles, but also volatile compounds contained directly in the glass. Moreover, the gas composition can be modified by reactions between the released gases and the glass melt. Published data indicate that besides CO₂ and/or CO in the bubbles, another carbon reservoir is present directly in the tektite glass. To clarify the problem of carbon content and carbon isotopic composition of the tektite glass, three samples from the Central European tektite strewn field—moldavites—were analyzed. The samples contained only 35–41 ppm C with δ¹³C values in the range from ?28.5 to ?29.9‰ VPDB. This indicates that terrestrial organic matter was a dominant carbon source during moldavite formation.     

A local spatial decision support system for developing countries based on MCA,fuzzy sets and OWA – case study of a municipality in Cuba

This paper presents a Spatial Decision Support System for local governments of developing countries. It allows municipality government, enterprises, scientific community and civil society to address decision problems using GIS. The framework is supported by four modules of information technologies: Environmental Decision Support Database, Data Manipulation, Decision Support, and Mapping. A case study is presented covering the implementation of this framework in one municipality of Cuba. An example of land suitability planning for coconut crops is used to evaluate the system performance and usability. Results show local municipalities are able to use this framework to solve local decision problems using state of the art decision making even with low infrastructure development.     

Automicrite in a ‘nummulite bank’ from the Monte Saraceno (Southern Italy): evidence for synsedimentary cementation

Following introduction of the term ‘nummulite bank’, there has been debate regarding interpretation of these types of deposits as autochthonous (automicrite) or allochthonous (detrital micrite). These banks are made up of large foraminifera and ill‐defined fine‐grained components. The fine‐grained components consist mainly of micrites. The recognition of automicrite has deep implications for the synsedimentary cementation and stabilization of the bank. In order to distinguish between automicrite and detrital micrite, the nanomorphology, geochemistry and organic matter remains in the microfacies of a nummulite bank in the Middle Eocene of Monte Saraceno (Gargano, Southern Italy) were analysed. Optical and scanning electron microscope investigations showed that the micrites have been recrystallized to aggrading microsparite. Epifluorescence observations on selected micrite/microsparite areas with peloidal texture revealed the presence of organic matter. Scanning electron microscope analyses on epifluorescent micrites showed that the microbial peloids have smaller crystal sizes than those in organic matter‐depleted areas. The geochemical characterization of extracted organic matter, performed through the functional group analyses by Fourier transform‐infrared spectroscopy, shows strong prevalence of the aromatic fraction over the aliphatic and carboxylic ones. These characteristics of organic compounds indicate both their thermal maturation and their likely derivation from degradation of bacterial communities. The local presence of peloidal anti‐gravity textures, bright epifluorescence and organic molecules in clotted peloidal areas suggest that the metabolic activity of microbial communities could have induced precipitation of these micrites and, consequently, the syndepositional cementation of the nummulite bank. This type of cementation can rapidly stabilize sediments and promote the depositional bank geometry.