70万年来西太平洋暖池北缘有孔虫氧碳同位素特征及其古海洋学意义

选取西太平洋暖池北缘西菲律宾海本哈姆高原的MD06-3047B孔沉积物柱状样为研究材料,通过分析70万年来有孔虫氧碳同位素变化特征发现:在M1S 14～ 13期,西菲律宾海由于受夏季风影响增强,可能存在上升流活动;在冰期终止期Ⅰ、Ⅱ、Ⅳ和Ⅴ期出现Pulleniatina obliquiloculata δ13C极小值事件,表明在这几个冰期终止期来自南极的低δ13C海水到达了西太平洋暖池北部边缘地区.次表层种P.obliquiloculata与表层种Globigerinoides ruber 氧同位素差值恢复的温跃层变化具有冰期逐渐变浅,间冰期逐渐变深的特点.进一步将其与西太平洋暖池核心区ODP805站和赤道东太平洋ODP847站的次表层、表层有孔虫氧同位素差值进行对比,结果显示在过去70万年来西太平洋暖池效应逐渐加强,并且存在长时间尺度的类厄尔尼诺-南方涛动(ENSO)式变化,冰消期时表现为类厄尔尼诺状态.     

Characteristics of low frequency oscillations of the atmosphere-ocean coupling

The low frequency oscillation of latent heat flux over the tropical oceans has been studied. The NCEP reanalyzed fields of wind and humidity alongwith Reynolds SST are used to compute the instantaneous as well as monthly mean surface latent heat fluxes (LHF) for the year 1999. The procedure of LHF computation is based on bulk method. Spectral analysis shows that significant energy is contained in Madden Julian Oscillation band in the winds, SST, moisture and in the latent heat flux. The global distribution of wind, humidity, SST and LHF oscillation on the time scale of 30–50 days are analyzed. Maximum amplitude of oscillation on this time scale in all the above mentioned parameters were found over the Indian Ocean. The fluctuation of surface wind speed and moisture controls the latent heat flux on this time scale. The fluctuation of SST on this time scale does not seem to be important over most of the oceans.     

The North Atlantic Oscillation (NAO) and Europe Blocking and Their Impacts on Extreme Snowstorms: A Review

Large-scale, low frequency modes such as the North Atlantic Oscillation(NAO)and blocking, have an important modulation on the northern hemisphere weather and climate. In this paper, the physical mechanism studies on inter-decadal and decadal variability of NAO and blocking were summarized. The relationship between NAO regime transitions and the interannual variability of NAO in winter during was examined by using a statistical approach. The time-space relationship between NAO and European blocking were discussed. Based on two extreme cold and snowstorm events, the impacts on local weather especially the extreme events within the life cycle (two weeks) of the NAO and blocking were further examined. It was found that the frequently occurrence of the Eurasian extreme snowstorm was closely related to the special combination of NAO and blocking regime. In addition, the development of theoretical modes for NAO and blocking was discussed and issues that remain to be solved were proposed.     

北大西洋涛动和北极涛动与新疆河川径流变化

分析了冬季北大西洋涛动(NAO)和北极涛动(AO)与新疆天山南北不同流域河川径流变化的关系.结果表明:影响北半球气温、降水等气候驱动因子的NAO和AO同样与新疆河川径流的变化具有显著的遥相关.在年际变化上,NAO和AO的强弱分别与径流变化的相关性具有明显的区域性差异;在年代际尺度上,NAO和AO有超前于新疆河流年径流5 a的显著相关,相关关系分别超过了95%和99%置信水平.NAO和AO变化对预测新疆河川径流的变化有很好的实际意义.     

Seasonal and Interannual Sea Surface Temperature Variability in the Coastal Cities of Arabian Sea and Bay of Bengal

The sea surface temperature (SST) variations play a veryimportant role in the genesis and maintenance of meteorological and oceanographic processessuch as monsoon depressions and subsequent floods, large-scale sea level fluctuationsand genesis of tropical cyclones. Many low lying coastal regions of South Asia are adjacentto river deltas and have large population. The dense population, poor economy and severalother socio-economic factors make these areas most vulnerable to the impact of climate change.Variability of sea surface temperature (SST) is importantas the duration and intensity of SST provide the basis for studies related to climatic changescenario. In this study an attempt has been made to estimate the recent SST trends in the coastalwaters of some cities, which lie on the Arabian Sea and Bay of Bengal. The annual andinterannual variability has also been studied. The SST variations have then been linkedwith the El Nino and La Nina events.The NOAA-NASA Pathfinder Advanced Very High Resolution Radiometer (AVHRR) SST fields from 1985-1998, created in the Jet Propulsion Laboratory(JPL), USA are used in this study. Here the quality of data is an important factor toobtain reliable estimates of Sea Surface Temperature (SST) trends and other related parameters.However, this is not possible with the conventional type data, due to low quality as wellas sparse data in the region. Though the satellite based SST climatologies have shorterobservation lengths, they can provide reliable estimates of recent SST variability overa large oceanic areas with sparse or no data.Increasing trend of SST is observed throughout all theseasons in the northern Arabian Sea extending from Oman to Karachi and Mumbai and furthersouth to Salalah and Colombo. However, in coastal islands stations further south ofIndia such as at Colombo the increment is not significant. Though the increasing trend in SSTduring winter is not significant, nevertheless it shows the increasing influence of coldspells on this Island. An interesting situation has been observed in the Bay of Bengal. On anaverage, increasing trends in the annual SST were observed in Visakhaputnam. But at thestations located in the northeastern part of Bay of Bengal, namely Hiron Point and Cox'sBazar reverse conditions are observed. In the Southern Bay of Bengal variations in SST isnot significant which reflects in the SST analysis of Chennai and Port Blair stations. Locationof these stations at lower latitudes (near by equator) probably is the reason for this insignificantchange. It has been found that the interannual mode of SST variations dominate the linear SSTtrends which is characterized by the El Nino Southern Oscillations (ENSO) scale cycle.     

Patterns of Pacific decadal variability recorded by Indian Ocean corals

We investigate Pacific Decadal Oscillation (PDO) signals recorded by two bimonthly resolved coral δ¹⁸O series from La Réunion and Ifaty (West Madagascar), Indian Ocean from 1882 to 1993. To isolate the main PDO frequencies, we apply a band pass filter to the time series passing only periodicities from 16 to 28 years. We investigate the covariance patterns of the coral time series with sea surface temperature (SST) and sea level pressure (SLP) of the Indian and Pacific Oceans. In addition, the empirical orthogonal functions of the filtered SST and SLP fields (single and coupled) are related to the filtered coral times series. The covariance maps show the typical PDO pattern for SST and SLP, confirming the coupling between the Indian and Pacific Oceans. Both corals show the strongest signal in boreal summer. The La Réunion (Ifaty) coral better records SST (SLP) than SLP (SST) pattern variability. We suggest that the filtered La Réunion coral δ¹⁸O represents δ¹⁸O of seawater that varies with the South Equatorial Current, which, in turn, is linked with the SST PDO. The filtered Ifaty coral δ¹⁸O represents SST and is remotely linked with the SLP PDO variability. A combined coral record of the Ifaty and La Réunion boreal summer δ¹⁸O series explains about 64% of the variance of the coupled SST/SLP PDO time series. AGU OS06 special issue “Ocean’s role in climate change—a paleo perspective”.     

Heterozoan carbonates from the equatorial rocky reefs of the Galápagos Archipelago

Strongly influenced by seasonal and interannual (i.e. El Niño‐Southern Oscillation) upwelling, the equatorial setting of the Galápagos Archipelago is divided into well‐defined temperature, nutrient and calcium carbonate saturation (Ω_aragonite) regions. To understand the relationship between oceanographic properties and sediment grain associations, grain size, carbonate content and components from sea floor surface samples were analysed, representing the main geographical regions of the Galápagos Archipelago. The shallow‐water rocky reefs of the Galápagos Archipelago are characterized by mixed carbonate–siliciclastic slightly gravelly sands. Despite minor differences in carbonate content, major differences exist in the distribution and composition of key carbonate producing biota. Halimeda is absent and benthic foraminifera occur in extremely low abundance. The western side of the Galápagos Archipelago is strongly influenced by nutrient‐rich, low‐Ω_aragonite, subtropical water, which generates a heterozoan carbonate biofacies in a tropical realm resembling cold‐water counterparts (i.e. serpulid, echinoderm, gastropod, barnacle and bryozoan‐rich facies). The Central East region is composed of a transitional‐heterozoan biofacies. Biofacies observed in the northern region have an increased occurrence of tropical corals, albeit with a minor overall contribution to the carbonate components. Although the temperature gradient would allow for a broader distribution of photozoan biofacies, the increased nutrient concentration and related reduced light penetration from the upwelled waters favour heterozoan carbonate factories, mimicking cool‐water, deeper or higher latitude environments. The recent sedimentary record of the Galápagos Archipelago presents a range of tropical heterozoan carbonate communities, responding to more than simply latitude or temperature but a much more complex mixture of physical, evolutionary and geological processes.     

青藏高原气候变化的若干事实及其年际振荡的成因探讨

利用1961-2012年青藏高原88个气象台站逐月气温、降水以及温室气体等气候系统监测资料和CMIP5输出的未来气候变化情景数据,分析了近52年来青藏高原气候变化暖湿化的若干事实,揭示了其年际振荡与温室气体、高原加热场、高原季风、AO等气候系统因子的关系,预测了未来20~40年青藏高原可能的气候变化趋势。研究表明：近52年来青藏高原在总体保持气候变暖的趋势下自2006年以来出现了某些增暖趋于缓和的迹象,较全球变化滞后了8年左右;降水量的增加在青藏高原具有明显的普遍性和显著性,气候变湿较变暖具有一定的滞后性,降水量变化的5年短周期日趋不显著,而12年、25年较长周期逐渐明显且仍呈增多趋势。由于温室气体、气溶胶持续增加、高原夏季风趋强、ENSO事件和太阳辐射减少,青藏高原气候持续增暖但有所缓和;春季高原加热场增强、高原夏季风爆发提前且保持强劲,使得高原春、夏季和年降水量增加,而秋、冬季AO相对稳定少动,东亚大槽强度无明显变化,高原冬季风变化不甚显著,导致了高原秋、冬季降水量无明显变化。未来20~40年青藏高原仍有可能继续保持气温升高、降水增加趋势。     

Lateglacial and early Holocene palaeoclimatic reconstruction based on glacier fluctuations and equilibrium‐line altitudes at northern Folgefonna,Hardanger, western Norway

Northern Folgefonna (c. 23 km²), is a nearly circular maritime ice cap located on the Folgefonna Peninsula in Hardanger, western Norway. By combining the position of marginal moraines with AMS radiocarbon dated glacier‐meltwater induced sediments in proglacial lakes draining northern Folgefonna, a continuous high‐resolution record of variations in glacier size and equilibrium‐line altitudes (ELAs) during the Lateglacial and early Holocene has been obtained. After the termination of the Younger Dryas (c. 11 500 cal. yr BP), a short‐lived (100–150 years) climatically induced glacier readvance termed the ‘Jondal Event 1’ occurred within the ‘Preboreal Oscillation’ (PBO) c. 11 100 cal. yr BP. Bracketed to 10 550–10 450 cal. yr BP, a second glacier readvance is named the ‘Jondal Event 2’. A third readvance occurred about 10 000 cal. yr BP and corresponds with the ‘Erdalen Event 1’ recorded at Jostedalsbreen. An exponential relationship between mean solid winter precipitation and ablation‐season temperature at the ELA of Norwegian glaciers is used to reconstruct former variations in winter precipitation based on the corresponding ELA and an independent proxy for summer temperature. Compared to the present, the Younger Dryas was much colder and drier, the ‘Jondal Event 1’/PBO was colder and somewhat drier, and the ‘Jondal Event 2’ was much wetter. The ‘Erdalen Event 1’ started as rather dry and terminated as somewhat wetter. Variations in glacier magnitude/ELAs and corresponding palaeoclimatic reconstructions at northern Folgefonna suggest that low‐altitude cirque glaciers (lowest altitude of marginal moraines 290 m) in the area existed for the last time during the Younger Dryas. These low‐altitude cirque glaciers of suggested Younger Dryas age do not fit into the previous reconstructions of the Younger Dryas ice sheet in Hardanger. Copyright © 2005 John Wiley & Sons, Ltd.     

Impact of Southern Oscillation on the Frequency of Monsoon Depressions in the Bay of Bengal

The impact of Southern Oscillation on thecyclogenesis over the Bay of Bengal duringthe summer monsoon has been investigated.The analysis of correlation coefficients(CCs) between the frequency of monsoondepressions and the Southern OscillationIndex (SOI) reveals that more depressionsform during July and August of El Niñoyears. Due to this, the seasonal frequencyof monsoon depressions remains little higherduring El Niño epochs even though thecorrelations for June and September are notsignificant. The CCs for July and August aresignificant at the 99% level.The El Niño-Southern Oscillation (ENSO)is known to affect Indian MonsoonRainfall (IMR) adversely. The enhancedcyclogenesis over the Bay of Bengal duringJuly and August is an impact of ENSO whichneeds to be examined closely. Increasedcyclogenesis over the Bay of Bengal may bereducing the deficiency in IMR duringEl Niño years by producing more rainfallover the eastern parts of India duringJuly and August. Thus there is a considerablespatial variation in the impact of ENSOon the monsoon rainfall over India and El Niñoneed not necessarily imply a monsoonfailure everywhere in India.The area of formation of monsoon depressionsshifts eastward during El Niño years.Warmer sea surface temperature (SST) anomaliesprevail over northwest and adjoiningwestcentral Bay of Bengal during premonsoon andmonsoon seasons of El Niño years.May minus March SOI can provide useful predictionsof monsoon depression frequencyduring July and August.     

Evidence of NAO control on subsurface ice accumulation in a 1200 yr old cave-ice sequence, St. Livres ice cave, Switzerland

Mid-latitude ice caves are assumed to be highly sensitive to climatic changes and thus represent a potentially interesting environmental archive. Establishing a precise chronology is, however, a prerequisite for the understanding of processes driving the cave-ice mass balance and thus allows a paleoenvironmental interpretation. At St. Livres ice cave (Jura Mountains, Switzerland), subfossil trees and organic material are abundant in the cave-ice deposit, therefore allowing the dating of individual ice layers. The dendrochronological analysis of 45 subfossil samples of Norway spruce (Picea abies (L.) Karst.) from the overhanging front of the ice outcrop as well as the dating of seven wood samples with ¹⁴C dating allowed for a reconstruction of the St. Livres cave-ice sequence and for the determination of periods of ice accumulation and ablation. Results suggest a maximal age of 1200 ± 50 ¹⁴C yr BP for the observed ice sequence and indicate the presence of four major deposition gaps dated to the 14th, 15th, mid-19th and late 19th century, which can be related with periods of positive North Atlantic Oscillation anomalies (NAO+) over the winter half-year and/or anthropogenic cave-ice abstraction. Similarly, there is evidence that periods of cave-ice accumulation as observed between AD 1877-1900 and AD 1393-1415 would correspond with phases of negative NAO indices. Cave ice represents therefore an original climate archive for the winter half-year and is complementary to other continental proxies recording preferentially summer conditions (e.g., tree rings, varves).     

Does the El Niño-Southern Oscillation control the interhemispheric radiocarbon offset?

Since the 1970s it has been recognised that Southern Hemisphere samples have a lower radiocarbon content than contemporaneous material in the Northern Hemisphere. This interhemispheric radiocarbon offset has traditionally been considered to be the result of a greater surface area in the southern ocean and high-latitude deepwater formation. This is despite the fact that the El Niño-Southern Oscillation (ENSO) is known to play a significant role in controlling the interannual variability of atmospheric carbon dioxide by changing the flux of ‘old’ CO₂ from the tropical Pacific. Here we demonstrate that over the past millennium, the Southern Hemisphere radiocarbon offset is characterised by a pervasive 80-yr cycle with a step shift in mean values coinciding with the transition from the Medieval Warm Period to the Little Ice Age. The observed changes suggest an ENSO-like role in influencing the interhemispheric radiocarbon difference, most probably modulated by the Interdecadal Pacific Oscillation, and supports a tropical role in forcing centennial-scale global climate change.     

Intra-Seasonal Oscillation (ISO) of south Kerala rainfall during the summer monsoons of 1901–1995

Time series of daily averaged rainfall of about 40 rain gauge stations of south Kerala, situated at the southern-most part of peninsular India between latitudes about 8‡N and 10‡N were subjected to Wavelet Analysis to study the Intra Seasonal Oscillation (ISO) in the rainfall and its inter-annual variability. Of the 128 days, 29th May to 3rd October of each of the 95 years 1901-1995 were analysed. We find that the period of ISO does not vary during a monsoon season in most of the years, but it has large inter-annual variability in the range 23 to 64 days. Period-wise, the years cluster into two groups of ISO, the SHORT consisting of periods 23, 27 and 32 days and the LONG with a single period of 64 days, both the sets at a significance level of 99%. During the 95 years at this level of significance there are 44 years with SHORT and 20 years with LONG periods. 11 years have no ISO even at the 90% level of significance. We composited NCEP SST anomalies of the summer monsoon season June to September for two groups of years during the period 1965–1993. The first group is of 5 years with a LONG ISO period of 64 days for south Kerala rainfall at significance level of 99% and the second group is of 12 years with SHORT ISO periods of 23, 27 and 32 days at the same level of significance. The SST anomaly for the LONG (SHORT) ISO resembles that for an El Nino (La Nina).     

Variations of Surface Air Temperature Over the Land Areas in and Around the Bay of Bengal

The inter-annual variation and linear trends of the surface air temperature in the regions in and around the Bay of Bengal have been studied using the time series data of monthly and annual mean temperature for 20–40 years period within 1951–1990. The study area extends from Pusma Camp of Nepal in the north and Kuala Lumpur of Malaysia in the south and between 80--100 ° E. The annual variation of temperature has also been studied using the mean monthly temperature for the variable time frames 1961–1975, 1976–1990 and 1961–1990. The trend of temperature has been analyzed using linear regression technique with the data from 1961–1990, which showed that the warming trend is dominant over the study areas except for a few stations. It has been found that Nepal shows predominant warming trends. Bangladesh and the adjacent areas of India and the northern part of Bay of Bengal adjacent to the Bangladesh coast have shown strong warming trends of the annual temperature with maximum at Dhaka (0.037 °C/year). The near equatorial zone, i.e., southern India, Sri Lanka and part of Thailand and Malaysia (Kuala Lumpur) shows warming trends in the annual mean temperature with strong warming at Pamban and Anuradhapura (around 0.04 °C/year). The cooling trends have been observed at a few stations including Port Blair, Yangoon and Cuttack. Further analysis shows the presence of prominent ENSO scale of variations with time period 4–7 years and 2–3 years for almost all the stations. The decadal mode with T >7 years is present in some data series. The results of the variations of temperature with respect to the Southern Oscillation Index (SOI) show that SOI has some negative correlation with temperature for most of the stations except those in the extreme northeast. It has been found that positive anomaly of temperature has been observed for El Niño events and negative anomaly for the La Nina events.     

1951—2016年中亚努尔苏丹与乌鲁木齐寒潮过程频数变化及其主要影响因子对比分析

利用1951—2016年努尔苏丹和乌鲁木齐的逐日最低气温资料,以当年7月到翌年6月为统计年,对比分析了中亚地区的努尔苏丹与乌鲁木齐的寒潮、强寒潮和超强寒潮过程频数气候变化特征,并初步分析了冬季北极涛动(AO)、北大西洋涛动(NAO)与中亚两个城市同期寒潮活动关系.结果显示:努尔苏丹的年平均寒潮过程频数(15.7次·a-...     

Does the Agulhas Current amplify global temperatures during super‐interglacials?

Future projections of climate suggest our planet is moving into a ‘super‐interglacial’. Here we report a global synthesis of ice, marine and terrestrial data from a recent palaeoclimate equivalent, the Last Interglacial (ca. 130–116 ka ago). Our analysis suggests global temperatures were on average ～1.5°C higher than today (relative to the AD 1961–1990 period). Intriguingly, we identify several Indian Ocean Last Interglacial sequences that suggest persistent early warming, consistent with leakage of warm, saline waters from the Agulhas Current into the Atlantic, intensifying meridional ocean circulation and increasing global temperatures. This mechanism may have played a significant positive feedback role during super‐interglacials and could become increasingly important in the future. These results provide an important insight into a future 2°C climate stabilisation scenario. Copyright © 2010 John Wiley & Sons, Ltd.     

克里金算法与多重分形理论在岩土参数随机场分析中的应用

岩土参数的空间分布特征由于存在取样数据之间自相关和互相关的特性,未知点的岩土参数属性可通过特定的方法内插或外推,经典的数理统计方法难以确定周围的数据样本点以及相应的插值系数。首先介绍地统计学中基于距离加权的普通克里金（ordinary kriging, OK）算法、泛克里金算法（UK）和协克里金算法（CK）。由于基于滑动距离加权的OK算法无法度量局部空间的奇异性,将引入多重分形理论弥补该缺陷。以2010上海世博会的世博轴区域（长525 m,宽80 m）为工程背景,区域内共有42个取土钻孔,以典型的粉质黏土层3个重要的物理力学指标,即黏聚力、内摩擦角和压缩模量验证以上算法。对于岩土参数黏聚力和内摩擦角,预测精度由高至低为多重分形联合模型（MK）、协克里金模型（CK）、泛克里金模型（UK）、普通克里金模型（OK）;对于岩土参数压缩模量,相应的顺序为泛克里金模型和普通克里金模型位置互换。研究结果证明,在岩土参数空间场的分析中,辅助信息有助于提高数据预测精度,并且多重分形联合模型有助于分析空间局部的奇异性。     

北大西洋涛动对青藏高原夏季降水的影响

利用青藏高原中东部1961-2004年60个气象台站夏季(6-8月)降水资料,通过旋转经验正交函数分解发现青藏高原夏季降水存在南北反向变化的空间模态,分析表明这种变化模态与北大西洋涛动(NAO)密切相关.利用NCEP/NCAR再分析资料进行环流场分析,探讨了NAO对青藏高原这种降水空间变化模态的影响机制.结果表明:强NAO年份时,高原北部水汽输送通量强度增强,水汽辐合增强,而高原南部水汽输送通量强度减弱,此时高原切变线位置明显偏北,正是在这种水汽输送和环流形式配置下使得高原北部降水偏多而高原南部降水偏少;在弱NAO年份,上述情况基本相反.     

Is the North Atlantic Oscillation reflected in Scandinavian glacier mass balance records?

The North Atlantic Oscillation (NAO) is one of the modes of climate variability in the North Atlantic region. The atmospheric circulation during the winter season in this region commonly displays a strong meridional (north–south) pressure contrast, with low air pressure (cyclone) centred close to Iceland and high air pressure (anticyclone) near the Azores. This pressure gradient drives the mean surface winds and the mid‐latitude winter storms from west to east across the North Atlantic, bringing mild moist air to northwest Europe. The NAO index is based on the difference of normalised sea‐level pressures (SLP) between Ponta Delgada, Azores and Stykkisholmur, Iceland. The SLP anomalies at these stations are normalised by division of each monthly pressure by the long‐term (1865–1984) standard deviation. Interannual atmospheric climate variability in northwest Europe, especially over Great Britain and western Scandinavia has, during the last decades, been attributed mainly to the NAO, causing variations in the winter weather over the northeast North Atlantic and the adjacent land areas. A comparison between the NAO index and the winter (December–March) precipitation between ad 1864 and 1995 in western Norway shows that these are strongly linked (correlation coefficient 0.77). Variations in the NAO index are also reflected in the mass balance records of glaciers in western Scandinavia. The NAO index is best correlated with mass balance data from maritime glaciers in southern Norway (e.g. Ålfotbreen R² = 0.51). The record of Holocene (last ca. 11 500 cal. yr) glacier variations of maritime glaciers in western Scandinavia is thus a proxy of pre‐instrumental NAO variations. Copyright © 2000 John Wiley & Sons, Ltd.     

页岩油(气)微尺度流动中的若干问题

本文调研了国内外近些年在页岩油(气)微尺度流动方面的研究成果。从分子动力学方法(MD)、格子玻尔兹曼方法(LBM)、孔隙网络模型(PNM)3种计算模型的角度展开分析,同时结合作者的前期工作,分析了影响页岩油(气)流动输运的关键因素,指出3种方法的局限性及存在的问题,认为PNM方法可作为微尺度流动研究的基础模型,并将3种方法之间的联系有机地体现在研究路线框图中,为页岩油(气)微尺度流动的研究指明了方向。