中亚干旱区陆地水资源对气候变化的响应

气候变化对中亚干旱区高山融雪、蒸散发以及径流等水循环过程产生影响,从而引起区域水资源在空间和时间上的重新分配.在归纳总结降水、土壤水、地表水、陆地水储量等不同水体类型在气候变化下改变情况的基础上,综述了中亚干旱区陆地水资源变化对气候变化响应的现状及进展.由于使用的数据和评估方法不同,水资源变化研究结果具有一致性及不确定...     

Tree‐ring‐based annual precipitation reconstruction for the Hexi Corridor,NW China: consequences for climate history on and beyond the mid‐latitude Asian continent

An annual (July to June) precipitation reconstruction for the period AD 1760–2010 was developed from a Picea crassifolia regional tree‐ring chronology from two sites in the northern mountainous region of the Hexi Corridor, NW China. This reconstruction explains 52.1% of the actual precipitation variance during the period 1951 to 2010. Spatial correlations with gridded land‐surface data reveal that our reconstruction contains a strong regional precipitation signal for the Hexi Corridor and for the southern margin of the Badain Jaran Desert. Significant spectral peaks were identified at 31.9, 11.1, 8.0, 7.0, 3.2, 2.6 and 2.2 years. A large‐scale comparison indicates that our reconstruction is more consistent with climate records of a Westerly‐dominated Central Asia, and that the Westerlies have a greater impact on the precipitation in this region than the Asian summer monsoon. Our reconstructed precipitation series is significantly correlated with sea‐surface temperature (SST) in the tropical Atlantic Ocean (positive), the tropical Indian Ocean (positive), the western tropical Pacific Ocean (positive), and the western North Pacific Ocean (negative). The spatial correlation patterns between our precipitation reconstruction and SSTs of the Atlantic and Pacific Oceans suggest a connection between regional precipitation variations and the high‐mid‐latitude northern atmospheric circulations (Westerlies and Asian summer monsoon).     

热带太平洋海洋环流与暖池的结构特征、变异机理和气候效应

热带西太平洋暖池是引发强烈的大气对流、驱动Walker环流和Hadley环流系统的主要热源之一,对全球、尤其是东亚气候有重要影响。针对我国在提升气候预测水平方面的重大和迫切需求,国家重点基础研究发展计划项目"热带太平洋海洋环流与暖池的结构特征、变异机理和气候效应"于2011年7月正式立项。项目拟解决的关键科学问题包括:①调控暖池形成和变异的海洋环流多尺度相互作用过程;②海洋动力过程在暖池热盐结构变异中的作用及其机理;③暖池变异对不同类型El Nio影响机理的异同和对东亚季风变异的调制机理。围绕上述关键科学问题,项目将以暖池变异为中心,关注影响和控制暖池结构与变异的关键海洋过程,以及暖池海气相互作用影响ENSO循环、东亚季风年际变异的过程和机理,重点组织开展以下3个方面有针对性的调查研究:①热带太平洋环流和暖池的结构和变异特征;②热带太平洋环流与暖池相互作用的关键过程和机理;③暖池变异的海洋—大气耦合过程及其气候效应。在此基础上,项目将力争阐明暖池影响东亚季风和我国气候变异的过程、机理与敏感区,改进模式的混合参数化方案,提出有效提高ENSO预报技巧的同化方案,为我国短期气候预测能力的提高提供科学支撑。     

Control of wind strength and frequency in the Aral Sea basin during the late Holocene

Changing content of detrital input in laminated sediments traced by XRF scanning and microfacies analyses reflect prominent variations in sedimentation processes in the Aral Sea. A high-resolution record of titanium from a core retrieved in the northwestern Large Aral Sea allows a continuous reconstruction of wind strength and frequency in western Central Asia for the past 1500 yr. During AD 450–700, AD 1210–1265, AD 1350–1750 and AD 1800–1975, detrital inputs (bearing titanium) are high, documenting an enhanced early spring atmospheric circulation associated with an increase in intensity of the Siberian High pressure system over Central Asia. In contrast, lower titanium content during AD 1750–1800 and AD 1980–1985 reflects a diminished influence of the Siberian High during early spring with a reduced atmospheric circulation. A moderate circulation characterizes the time period AD 700–1150. Unprecedented weakened atmospheric circulation over western Central Asia are inferred during ca. AD 1180–1210 and AD 1265–1310 with a considerable decrease in dust storm frequency, sedimentation rates, lamination thickness and detrital inputs (screened at 40-μm resolution). Our results are concurrent with changes in the intensity of the Siberian High during the past 1400 yr as reported in the GISP2 Ice Core from Greenland.     

中东亚中全新世气候与植被反馈作用:PMIP 2多模式结果分析

文章选取了参加国际古气候模拟比较计划(Paleoclimate Modeling Intercomparison Project,简称PMIP)的6个耦合气候模式的模拟结果,着重对中全新世中东亚干旱区以及东亚季风区的夏季气候变化(气温、降水)进行分析,探讨了植被反馈作用对这3个区域中全新世气候变化的影响.由于各个模式之...     

未来不同排放情景下气候变化预估研究进展

概述未来不同排放情景下气候变化预估研究的主要进展。首先,对用于开展气候变化预估研究的不同复杂程度的气候系统及地球系统模式及其模拟能力进行了简要的介绍,指出虽然目前气候系统模式在很多方面存在着较大的不确定性,但大体说来可提供当前气候状况的可信模拟结果;进而介绍了IPCC不同的排放情景,以及不同排放情景下全球与东亚区域气候变化预估的主要结果。研究表明,尽管不同模式对不同情景下未来气候变化预估的结果存有差异,但对未来50～100年全球气候变化的模拟大体一致,即全球将持续增温、降水出现区域性增加。在此基础上,概述了全球气候模式模拟结果的区域化技术,并重点介绍了降尺度方法的分类与应用。同时对气候变化预估的不确定性进行了讨论。最后,对气候变化预估的研究前景进行了展望,并讨论了未来我国气候变化预估研究的重点发展方向。     

Holocene temperature fluctuations in the northern Tibetan Plateau

Arid Central Asia (ACA) lies on a major climatic boundary between the mid-latitude westerlies and the northwestern limit of the Asian summer monsoon, yet only a few high-quality reconstructions exist for its climate history. Here we calibrate a new organic geochemical proxy for lake temperature, and present a 45-yr-resolution temperature record from Hurleg Lake at the eastern margin of the ACA in the northern Tibetan Plateau. Combination with other proxy data from the same samples reveals a distinct warm–dry climate association throughout the record, which contrasts with the warm–wet association found in the Asian monsoon region. This indicates that the climatic boundary between the westerly and the monsoon regimes has remained roughly in the same place throughout the Holocene, at least near our study site. Six millennial-scale cold events are found within the past 9000 yr, which approximately coincide with previously documented events of northern high-latitude cooling and tropical drought. This suggests a connection between the North Atlantic and tropical monsoon climate systems, via the westerly circulation. Finally, we also observe an increase in regional climate variability after the mid-Holocene, which we relate to changes in vegetation (forest) cover in the monsoon region through a land-surface albedo feedback.     

中亚黄土沉积与西风区末次冰期快速气候变化

气候快速变化过程与机制一直是古气候研究的热点科学问题,随着不同地区高分辨率地质记录的增多,年代学方法的改进,此类快速气候变化事件的区域差异性日益突出,对比和认识这些区域之间的变化细节,有助于认识快速气候变化的规律和驱动机制。文章以中亚黄土为主要研究对象,根据黄土沉积特征与现代气候特征,将中亚黄土分为西部、北部和东部3个亚区,在总结中亚西风区黄土古气候研究进展的基础上,回顾了近年来中亚地区末次冰期西风区气候突变事件研究现状与问题,初步探讨了在亚轨道尺度上末次冰期快速气候变化发生过程和机制。结果表明,粒度、矿物学、地球化学等指标均指示中亚这3个黄土亚区末次冰期确实存在千年尺度的快速气候波动信号,但在年代和变率上存在区域差异,这种差异除了缺乏精确的年代学控制外,还与区域水热组合和区域地形结构有关。这些冷暖的快速气候变化与北大西洋高纬地区冰盖收缩扩张、西伯利亚高压强度和范围的变化导致风动力变化和西风带南北迁移有关。今后需进一步加强高分辨率年代序列的建立,进一步遴选中亚黄土中有效的、能够独立反映风力强度、源区信息、古温度、古降水等代用指标,并结合古气候模拟试验研究其驱动机制。     

东亚地区区域气候模拟的研究进展

由于大气环流模式对东亚地区区域气候特征的模拟存在很大不足,采用区域气候模式模拟该地区特殊的季风气候成为目前发展的一个重要研究方向,并取得了显著的研究进展。通过回顾当前东亚地区区域气候模拟的现状,表明大部分区域气候模式都不同程度地模拟出了东亚季风区持续性洪涝现象的大尺度环流特征和演变过程,再现了东亚各主要气候区降水的年际、季节和季节内变化及主要雨带的季节进退和降水的时空演变特征。但是,大部分模式没能很好地模拟出大尺度特征的强度和量值,模拟的温度和降水存在系统性偏差。原因分析表明,进一步完善和改进区域气候模式的物理过程参数化方案及动力框架可以改善模拟效果。最后对区域气候模式未来的发展给出展望。     

Influence of Icelandic Low pressure on winter precipitation variability over northern part of Indo-Pak Region

Several studies demonstrate that North Atlantic Oscillation (NAO) has dominant influence on the variability of climate over Southwest Asia. We deconstruct the NAO into its two components, the Azores High and the Icelandic Low. Regional circulations are influenced by changes not only in the pressure but also the positions of the Azores High and the Icelandic Low. The results presented in this paper exhibit that significantly great portions of interannual variance of winter precipitation over Indo-Pak Region (consists of Northeast Pakistan and Northwest India) can be explained by including the contributions of the Icelandic Low pressure in addition to ENSO and AO. This contribution also explains the physical mechanisms to establish the relationships between the COA and regional climate by examining composite maps of large-scale circulation fields using NCEP/NCAR reanalysis data.     

气候变化和人类活动对中亚地区水文环境的影响评估

中亚地区是我国天气的上游区,生态环境异常脆弱,必须要保证该地区生态环境和资源安全,水资源安全首当其冲.研究和评估气候变化和人类活动对中亚地区水文环境的影响,具有重要的战略意义.近百年来中亚地区气候有暖湿化趋势,气温增温持续时间较长且增温幅度较大,近50a增暖更加明显(0.47℃·(10a)^-1),其中冬季增温最快,预估未来会延续变暖的态势;同时20世纪80年代之后降水量持续波动上升.气候变化对该地区水资源的时空分布及湖泊变迁造成了重大影响,人类活动加剧了水资源短缺,近50a来锡尔河和阿姆河入咸海径流量均呈减少的趋势,20世纪70年代之后拦水蓄水水库等水利工程的建设,加上灌溉用水的增加,导致两河入咸海水量骤减;而1987年之后两河入咸海水量回升,主要是气温回暖、降水增多,加速了常年积雪和冰川融化,使得进入河道的径流量增加.同时,湖泊水位下降,面积收缩,水质恶化.中亚水资源问题主要是跨国水资源分配和水环境恶化问题,要做好水资源评估和用水规划工作,建立覆盖全区域的水资源环境监测网络.中亚国家需要共同参与制定一套完整的、综合考虑人口、社会经济、生态环境等因素的水资源管理政治立法决策体系,构建中亚各国人水和谐、互利共存的水资源新秩序,以水资源可持续利用来支持经济与社会的可持续发展.     

Water reservoirs, irrigation and sedimentation in Central Asia: a first-cut assessment for Uzbekistan

Water reservoirs play an important role in areas with limited and erratic precipitation where water is stored and re-distributed later for different purposes. Irrigation is primarily a major water consumer in arid countries of Central Asia for the economic development, employment and food security of the region. The major rivers of Central Asia (e.g., Amu Darya, Syr Darya, and Zerafshan) are turbid watercourses. Sedimentation reduces the main reservoir asset i.e., its volume capacity. In addition, vast territories of the region’s countries have been transformed for agriculture to grow water intensive crops such as cotton, rice and wheat during the Soviet Union that dramatically accelerated soil erosion by water and wind. Thus, many man-made water reservoirs are affected by high sedimentation rates. Moreover, uneven spatial and temporal water resources and a Soviet-inherited unified hydraulic infrastructure have raised transboundary reservoir management issues over water resources allocation among the countries in the region such as Kyrgyzstan, Tajikistan, Kazakhstan, Uzbekistan and Turkmenistan. The rivers such as Syr Darya and Amu Darya are already regulated by more than 78 and 94 %, respectively and attempts for new reservoir projects upstream raises increased concerns of the downstream countries (e.g., the Rogun hydropower station in Tajikistan and the Toktogul reservoir in Kyrgyzstan). For instance, the uncoordinated use of reservoirs has caused the Arnasai lake problem in Uzbekistan with environmental, material damage and social unrest. The aim of this paper is first to review the present conditions and the role of man-made water reservoirs for irrigation in Central Asia with special focus on Uzbekistan, second to document past and current reservoir sedimentation conditions in Uzbekistan and third to discuss research carried out by Soviet and present-time local research community in the domain of erosion and sedimentation in the region.     

Geochemical compositions of soluble salts in aeolian sands from the Taklamakan and Badanjilin deserts in northern China, and their influencing factors and environmental implications

Two large sandy seas in northern China, the Taklamakan and Badanjilin deserts, were investigated for geochemical variations of soluble salts in aeolian sands. The aim was to explore factors influencing the composition and distribution of soluble salts in aeolian sands and their environmental implications. The total concentrations of soluble salt in the aeolian sands range between 0.14 and 1.32‰, with pH ranging between 8.4 and 9.6, indicating a primary degree of salt accumulation and alkaline soil conditions in these regions. Sodium chloride and bicarbonate are the major salts. High inter-regional homogenization and small local differences in the chemical compositions and distributional patterns of salt occur in the two deserts. The spatial variations in salt content correlate with regional climatic parameters, such as precipitation and temperature. This suggests that the regional air temperature and moisture conditions of climate have a significant influence on the soluble salts in aeolian sands. The domination of sedimentation of soluble salts in aeolian sands deposited via atmospheric processes, which is heavily associated with dry deposition, is discussed. Case studies from the two deserts suggest that variations in salt content in sedimentary sequences, interlaid by aeolian and lacustrine sediments, should be interpreted with care if the aim is to reveal palaeo-environmental changes. To a certain extent, the two deserts, as inferred from the carbon-bearing salts and the alkalinity of the sandy soils, appear to have potential to provide a significant contribution to the global carbon cycle.     

Environmental change modelling for Central and High Asia: Pleistocene, present and future scenarios

A regional modelling concept was developed for late Quaternary climate reconstructions and future climate impact assessments. Based on estimates of different climate parameters covering the entire Central and High Asia in a grid-cell spacing of 1 km², climatic determinants of the recent spatial distribution of climate-sensitive environments (glacial and periglacial environments, forest) were explored. Simple climatic threshold functions were established, defining critical climate values for modelling the spatial extension of environments considered. Using palaeogeomorphological indicators as a basis, late Quaternary climatic conditions were modelled in a Last Glacial Maximum (LGM) scenario consistent with palaeogeomorphological and palaeoclimatological data. The results enabled a validation of LGM palaeoclimate simulations performed by the ECHAM GCM. To assess the magnitude of possible future climatic impacts on the spatial distribution of glaciers, permafrost and potential forest stands, two GCM-based IPCC-SRES climate change scenarios (IPCC special report on emission scenarios) for the time period 2070-2099 were considered. Assuming future climates to be perturbed for long enough to affect the environments, a distinct loss of glaciated areas and permafrost must be expected.     

全球大气季节内振荡对长江流域持续暴雨影响的研究进展

在引证论述大气季节内振荡(ISO)对暴雨(强降水)重要作用的基础上,概括性地回顾影响长江流域持续暴雨的大气ISO基本特征及其形成机制的主要成果。重点针对全球热带内外不同时间尺度的大气ISO的空间变化和年际变化与长江流域持续暴雨之间联系的研究工作进行总结评述,较为完整地总结长江流域夏季降水季节内变化的气候特征和全球不同空间和时间尺度的ISO对东亚副热带地区持续暴雨影响的已有认识,并结合2个半球的ISO与长江流域持续暴雨关系的研究现状,对未来暴雨(强降水)与不同时尺度ISO相互作用及其在10～30 d延伸期预报中的应用中有价值的科学问题和研究热点进行探讨,以期强调南半球ISO变化在全球和东亚副热带气候系统中的重要地位,提高夏季长江流域持续暴雨10～30 d延伸期预报和旱涝气候预测准确率。     

亚洲中部干旱区全新世气候变化的西风模式* ——以新疆博斯腾湖记录为例

位于受西风环流显著影响区的我国最大内陆淡水湖——新疆博斯腾湖提供了全新世亚洲中部干旱区气候变化的可靠记录。对该湖钻探岩芯、沉积年代以及孢粉、碳酸盐含量、粒度等代用指标分析结果表明,末次冰消期到全新世早期湖泊干涸,风砂沉积盛行,气候干旱;约8cal.kaB.P.以来现代湖泊形成,气候相对湿润,其中,约6.0~1.5cal.kaB.P.期间代用指标A/C值指示的流域湿度增加,盘星藻指示的湖泊深度最大,全新世最湿润时段发生在中晚全新世。博斯腾湖记录的早全新世干旱和中晚全新世湿润的气候框架得到中亚其他较高分辨率湖泊记录的支持,具有普遍性。亚洲中部西风影响区这一全新世气候变化框架与亚洲季风区早中全新世夏季风强盛、中晚全新世季风衰落的变化模式显著不同,具有近似反相位(out of phase)变化特征。广大中亚内陆干旱区中晚全新世湿润气候不大可能是东亚季风深入内陆造成的,更可能是通过西风环流与高纬度北大西洋相联系,其驱动机制需要更深入研究。     

Water storage loss in central and south Asia from GRACE satellite gravity: correlations with climate data

Recent decrease of water supply in central Asia and south Asia affects billions of people here. By filtering the errors at higher frequency components and correcting for the contaminated components, we enhance the monthly GRACE gravity fields to improve the determination of change in equivalent water height (EWH). The water storage changes from GRACE and the GLDAS hydrology model all show decreasing trends in this region. At the annual and inter-annual time scales, significant correlations between the variations in EWH and the variations in temperature, precipitation and snow equivalent height are found, especially at high altitude stations, suggesting that climate change is the driving factor for the water depletion in central Asia and south Asia.     

气候系统模式FGOALS_gI模拟的小冰期气候

利用1650～1750年逐年变化的太阳辐照度等外强迫资料,驱动中国科学院大气物理研究所LASG发展的快速气候系统模式FGOALS_gl,模拟了小冰期(LIA)气候.把模拟的LIA表面温度变化与重建资料进行对比,结果表明FGOALS_gl对LIA气候具有较强的模拟能力,说明太阳辐照度的自然变化是导致小冰期气候的重要成因.模拟结果显示,LIA时期纬向平均温度变化表现为整个对流层降温,低纬度地Ⅸ的降温中心位于对流层中层,北半球降温幅度大于南半球,高纬地区的降温幅度大于低纬地区.分析发现,中高纬地区的局地温度变化主要与环流异常相对应的冷暖平流有关;低纬地区的降温主要与赤道东风加强有关,东风增强通过增大蒸发和引起次表层冷海水上翻而令表层温度降低.LIA时期的降水变化丰要位于中低纬地区,表现为日界线东(西)侧降水的负(正)异常.与降水异常相对应.Walker环流加强,东太平洋对流活动减弱,它与低纬地区对流层中层冷异常相联系.与大气层顶净短波辐射异常的季节变化相对应,南、北半球夏季平均表面温度异常较之冬季低0.28℃左右.     

青藏高原南部冰芯记录与大气环流的关系*

通过念青唐古拉峰拉弄冰川垭口处(30°24'30″N, 90°34'12″E;海拔5850m)长度为29.5m的冰芯记录,恢复了1952~1998年间大气降水δD和净积累量的时间变化序列。上述两组序列与NCEP/NCAR气候资料的相关分析表明:δD和净积累量与中亚冬季的气压、南亚和青藏高原冬季、夏季的位势高度关系密切。中亚地区冬季气压的升高以及冬、夏季南亚和青藏高原位势高度的异常增强了印度夏季风,导致了念青唐古拉峰地区20世纪80年代以来降水量的增多和降水中δD值的降低。根据念青唐古拉冰芯δD和净积累量记录及其与亚洲地区大气环流的关系,可以通过青藏高原南部较长的冰芯记录来恢复过去该地区大气环流变化的历史。     

Characteristics and sources of atmospheric composition based on precipitation chemistry in the Shiyang River Basin,Northwestern China

Through collected precipitation samples continuously to research the precipitation chemical characteristics and the water vapor source in Shiyang River Basin, Northwestern China, a total of 121 precipitation samples had been collected in the Shiyang River Basin from July 2013 to July 2014. The results showed that, during the period of sampling, the variation range of pH value of precipitation ranged from 6.62 to 8.53 in Shiyang River Basin and the average was 7.46. The EC values ranged from 17.28 to 787.00 μs/cm, with a mean 186.66 μs/cm. Ca²⁺ and Na⁺ dominated cations and accounted for 71.80% of total cations composition, while SO₄ ^2? and NO₃ ^? dominated anions with a contribution of 82.18%. The main ionic sources are local dust aerosols and the dust from Central Asia and Northwestern China arid regions brought by the westerly, and the back trajectories also supported it. Back trajectories suggested that the air mass arrived in Shiyang River Basin mainly from the dust sources region in Central or West Asia or Northwestern China through westerly circulation in dry season, while from the Indian Ocean or the Pacific Ocean through monsoon circulation in wet season. The precipitation can be divided into three types based on the vector of water vapor transportation: the monsoon precipitation, the westerly precipitation, and the interaction precipitation (precipitation influenced both by monsoon and westerly). The type of interaction precipitation was major precipitation patterns in study area, and the westerly precipitation came next. The results are also helpful for further understanding the air pollution situation caused by dust events in study area and providing scientific basis for the effective prevention and control of atmospheric pollution.