Abrupt uplift of Tibetan Plateau at the end of early Pleistocene and Australasian impact event

The latest sharp uplift of the Tibetan Plateau and adjacent mountains occurred at the end of the early Pleistocene. The uplift of the Plateau resulted from Late Mesozoic-Cenozoic compressional structure due to the subduction of the Indian Plate beneath the Asian continent. This event definitively effected the formation of basin-mountain relief, Cenozoic basin deformation, large scale aridity and desertification of western China. The Australasian meteorites impact event happened ca. 0.8 Ma ago, located in the triangle area of the Indian Ocean ridge （20°S/67°E）. The impact may have resulted in an acceleration of speeding of the Indian Ocean ridge pushing the Indian Plate to subduct rapidly northward. Thus, the impact event can give reasonable explanation for the dynamic background of the latest rapid uplift of the Tibetan Plateau and the continental deformation of western China and even of the Middle Asia.     

Active tectonics and erosional unloading at the eastern margin of the Tibetan Plateau

Introduction The eastern margin of the Tibetan Plateau, adjacent to the Sichuan Basin (Figure 1), has become a testing ground for a variety of models that contrast mechanisms of extrusion and crustal thickening associated with the India-Asia collision (Avouac and Tapponnier 1993, England and Houseman 1986),but that also address the extent to which the upper crust and upper mantle are coupled (Royden et al. 1997, Holt 2000). The margin is characterized by topographic relief of over 5 km an…     

Evaluation of ERA-interim monthly temperature data over the Tibetan Plateau

In this study, surface air temperature from 75 meteorological stations above 3000 m on the Tibetan Plateau are applied for evaluation of the European Centre for Medium-Range Weather Forecasts(ECMWF) third-generation reanalysis product ERA-Interim in the period of 1979-2010. High correlations ranging from 0.973 to 0.999 indicate that ERA-Interim could capture the annual cycle very well. However, an average root-meansquare error(rmse) of 3.7°C for all stations reveals that ERA-Interim could not be applied directly for the individual sites. The biases can be mainly attributed to the altitude differences between ERA-Interim grid points and stations. An elevation correction method based on monthly lapse rates is limited to reduce the bias for all stations. Generally, ERA-Interim captured the Plateau-Wide annual and seasonal climatologies very well. The spatial variance is highly related to the topographic features of the TP. The temperature increases significantly(10°C- 15°C) from the western to the eastern Tibetan Plateau for all seasons, in particular during winter and summer. A significant warming trend(0.49°C/decade) is found over the entire Tibetan Plateau using station time series from 1979-2010. ERA-Interim captures the annual warming trend with an increase rate of 0.33°C /decade very well. The observation data and ERA-Interim data both showed the largest warming trends in winter with values of 0.67°C/decade and 0.41°C/decade, respectively. We conclude that in general ERA-Interim captures the temperature trends very well and ERA-Interim is reliable for climate change investigation over the Tibetan Plateau under the premise of cautious interpretation.     

青藏高原植被变化特征及其对气候变化的影响

利用1982-2001年美国国家航天航空局(NASA)的归一化植被指数(NDVI)资料以及55个青藏高原地区气象台站实测的最高气温、最低气温、平均气温和降水资料,初步分析了青藏高原地区各季节植被变化特征及其对气候变化的影响,通过分析发现,各季节青藏高原地区NDVI均以增长为主.特别是高原南部、北部和西部等地区增加明显,高原中东部地区植被有所减少.通过相关分析和台站概率相关分析发现,高原冬季和春季NDVI与后期春季和夏季的最高气温、最低气温、平均气温和降水有较好的正相关关系,但有的表现在相关系数比较显著,有的表现为概率相关较明显.     

Variations in soil temperature at BJ site on the central Tibetan Plateau

The temporal and spatial variation in soil temperature play a significant role in energy and water cycle between land surface and atmosphere on the Tibetan Plateau.Based on the observed soil temperature data(hourly data from 1 January 2001 to 31 December 2005)obtained by GAME-Tibet,the diurnal,seasonal and interannual variations in soil temperature at BJ site(31.37°N,91.90°E;4509 m a.s.l.)near Naqu in the central Tibetan Plateau were analyzed.Results showed that the average diurnal variation in soil temperature at 4 and 20 cm depth can be described as sinusoidal curve,which is consistent with the variation of solar radiation. However,the average diurnal variation in soil temperature under 60 cm was very weak.The average diurnal amplitude in soil temperature decreased by the exponential decay function with the increase of soil depth(R2=0.92,p<0.01).It is demonstrated that the average diurnal maximum soil temperature decreased by the exponential decay function with the increase of soil depth(R2=0.78,p<0.01).In contrast, the average diurnal minimum soil temperature increased by the exponential grow function with increasing of soil depth(R2=0.86,p<0.01).There were a linear negative correlation between the average annual maximum Ts and soil depth(R2=0.96, p<0.01),a logarithmic function relationship between the average annual minimum soil temperature and soil depth(R2=0.92,p<0.01).The average seasonal amplitude in soil temperature followed the exponential decay function with the increase of soil depth(R2=0.98,p<0.01).The mean annual soil temperature in each layer indicated a warming trend prominently.During the study period,the mean annual soil temperature at 4,20,40,60,80,100,130, 160,200 and 250 cm depth increased by 0.034,0.041, 0.061,0.056,0.062,0.050,0.057,0.051,0.047 and 0.042°C/a,respectively.     

Pollen-based reconstructions of Holocene vegetation and climatic change of Tibetan Plateau

A synthesis of Holocene pollen records from the Tibetan Plateau shows the history of vegetation and climatic changes during the Holocene. Palynological evidences from 24 cores/sections have been compiled and show that the vegetation shifted from subalpine/alpine conifer forest to subalpine/alpine evergreen sclerophyllous forest in the southeastern part of the plateau; from alpine steppe to alpine desert in the central, western and northern part; and from alpine meadow to alpine steppe in the eastern and southern plateau regions during the Holocene. These records show that increases in precipitation began about 9 ka from the southeast, and a wide ranging level of increased humidity developed over the entire of the plateau around 8-7 ka, followed by aridity from 6 ka and a continuous drying over the plateau after 4-3 ka. The changes in Holocene climates of the plateau can be interpreted qualitatively as a response to orbital forcing and its secondary effects on the Indian Monsoon which expanded northwards     

Seasonal and Spatial Variability of Microparticles in Snowpits on the Tibetan Plateau, China

The work presents microparticle concentrations in snowpits from the East Rongbuk Glacier on Mt. Qomolangma (Everest) (ER) (28.02°N, 86.96°E, 6536 m a.s.l.), the Zhadang Glacier on Mt. Nyainqentanglha (NQ) (30.47°N, 90.65°E, 5800m a.s.l.), and the Guoqu Glacier on Mt. Geladaindong (GL) (33.95°N, 91.28°E, 5823m a.s.l.) over the Tibetan Plateau (TP). Variations of microparticle and major ions (e.g. Mg2+, Ca2+) concentrations in snowpits show that the values of the microparticles and ions in the non-monsoon seasons are much higher than those in the monsoon seasons. Annual flux of microparticle deposition at ER is lower than those at NQ and GL, which could be attributed to the long distance away from the possible dust source regions as well as the elevation for ER higher than the others. Compared with other remote areas, microparticle concentrations in the southern TP are much lower than those in the northern TP, but still much higher than those in Greenland and Antarctica. The seasonal and spatial microparticle variations are clearly related to the variations of atmospheric circulation according to the air mass 5-day backward trajectory analyses of HYSPLIT Model. Resultingly, the high microparticle values in snow are mainly attributed to the westerlies and the strong dust storm outbreaks on the TP, while the monsoon circulation brings great amount of precipitation from the Indian Ocean, thus reducing in the aerosol concentrations.     

ANALYSIS OF MESOSCALE CONVECTIVE SYSTEMS OVER TIBETAN PLATEAU IN SUMMER

1INTRODUCTION In meteorological satellite cloud images, the features of Mesoscale Convective System (MCS) are shown in white bright cloud cluster, cloud band, cloud line, vorti- calcloudsystem,etc. The MCSlife cycle and spatial size usuallyvaryfrom several hours to one day and 100km to approximately 1000km, respectively. In the last two decades, it has been proven that storm and intensive con- vective weather, such as spasmodic thunderstorm and gale, tornado and short macro-precipitati…     

青藏高原城镇化格局的时空分异特征及影响因素

研究青藏高原城镇化格局的时空分异及其影响因素,有利于推动青藏高原现代人类活动时空过程的认知,对青藏高原就地就近城镇化及可持续发展具有参考意义。根据历次人口普查数据,本研究构建青藏高原县市尺度城镇化空间数据集,参考城镇化发展阶段,采用LISA空间类型划分法和空间计量回归模型,系统分析1990-2010年青藏高原内部城镇化格局的时空分异特征及影响因素。主要结论包括：① 青藏高原整体城镇化水平偏低,2017年底,青藏高原主体部分青海省和西藏自治区的常住人口城镇化水平分别为53.07%和30.8%,低于全国同期水平的58.52%,但青藏高原内不乏高水平城镇化地区,而且各地区间城镇化水平的空间差异缩小;② 青海西部柴达木盆地是高水平城镇化集聚区,羌塘地区是低水平城镇化集聚区,地级行政中心所在县市多呈现自身高、周边低的城镇化格局;③ 与内地相似,第二、三产业从业机会是推动青藏高原城镇化发展重要因素,社会公共服务资源对城镇化拉动作用开始凸显。研究结果可以为青藏高原人类活动研究和青藏高原就地就近城镇化可持续发展政策提供参考。     

基于卫星观测的两例青藏高原低涡结构的初步分析

应用风云2C卫星云图和配有云顶亮温的MTSAT卫星红外云图,描述了两例青藏高原低涡形成、发展及消亡过程,云图清晰显示了高原低涡具有涡眼和暖心结构的特征,并利用水汽图分析揭示了缺乏水汽供应是导致这类低涡不能进一步发展并移出高原的重要原因.最后用1°×1°NCEP分析资料对高原低涡形成眼结构时的基本物理场进行了诊断计算.结果表明:低涡整体为上升气流,而涡眼区在近地层为下沉气流,上层为相对涡区较弱的上升气流;低层辐合,高层辐散.进而印证了动力学研究工作得出的高原低涡具有与热带气旋类低涡(TCLV, tropical cyclone-like vortices)类似的涡眼和暖心结构特征的结论.     

多尺度视角下的青藏高原水资源短缺估算及空间格局

青藏高原水资源总量丰富,但由于水资源量与用水量在空间上分布不均衡,部分人口、城镇密集地区水资源短缺严重。本研究在多源数据的基础上,通过空间分析、降尺度处理等,建立了青藏高原省区、市域、县域空间尺度的水资源与用水量数据集。通过比较5、10、20、30年重现期多空间尺度的水资源短缺程度,分析水资源短缺在青藏高原的尺度效应,揭示青藏高原水资源短缺格局与特征,识别面临水资源短缺的人口与面积。结果表明,青藏高原在省区尺度无水资源短缺;在15个市域单元中,有3个市域出现水资源短缺;在115个县域单元中,有29个县域呈现出不同程度的水资源短缺,水资源短缺县域主要集中在青海省的河湟谷地、柴达木盆地与西藏自治区的一江两河流域等人口、城镇密集区域。总体而言,由于较大空间尺度地理单元内部各县域用水强度差异,在县域尺度面临水资源短缺的人口与面积大于市域与省区尺度面临水资源短缺的人口与面积。以县域为基本单元,发现青海省与西藏自治区30年重现期面临水资源短缺的人口占总人口的56.4%,出现水资源短缺的面积占总面积的10.4%。县域之间水资源短缺指数秩相关系数计算结果显示,省区内部各县域同时出现水资源短缺的可能性较大,而省区之间各县域同时出现水资源短缺的可能性相对随机。研究结果为制定青藏高原水资源短缺管理对策、促进区域城镇化与资源环境协调发展提供科学依据。     

青藏高原冬季植被变化与南亚夏季风关系分析

利用1982年1月-2001年12月青藏高原植被归一化指数(NDVI)和NCEP/NCAR再分析月平均资料,应用相关分析、奇异值分解(SVD)和经验正交分解(EOF)的方法,分析了青藏高原冬季的NDVI变化与南亚夏季风的关系.通过分析表明,高原植被与南亚地区850hPa纬向风场和纬向风垂直切变(U850hPa-U200hPa)有比较好的正相关关系.用纬向风垂直切变EOF分析的第一特征向量对应的时间系数定义一个南亚夏季风指数(EOFI),该系数与高原冬季NDVI相关较好,而且能较好地反映南亚夏季风的变化.     

青藏高原旅游经济与生态环境协调效应测度及交互胁迫关系验证

青藏高原地区壮美的自然风光、神奇的人文景观和独特的民族文化,使其成为国内外旅游者倾心向往的世外桃源,亟需进一步探究其旅游经济与生态环境之间的交互耦合关系。本文创建青藏高原旅游经济与生态环境综合评价指标体系,采用青海省和西藏自治区15个地市州2000-2017年面板数据探究旅游经济与生态环境协调效应及交互胁迫关系。结果显示： ① 2000-2017年青藏高原仅有拉萨和西宁旅游经济指数呈现快速增长趋势,其余地市州均呈现缓慢增长趋势,生态环境指数整体较高,仅有西宁和海东呈现波动增长趋势,其余地市州变化平缓;② 青藏高原旅游经济与生态环境复合系统协调度时序上呈现波动增长趋势,空间上呈现南高北低、东高西低的分布格局;青海呈现以西宁为核心,逐层向外递减的核心-边缘空间格局;西藏呈现以拉萨为中心,南高北低的空间格局;③ 青藏高原复合系统协同效应子类型主要是旅游经济滞后型,西宁和拉萨呈现“旅游经济滞后-系统均衡发展-生态环境滞后”的变化趋势;④ 基于双指数模型证实了青藏高原旅游经济与生态环境之间具有交互胁迫关系。     

青藏高原湖泊面积动态监测

高原湖泊的动态变化对区域水循环具有重要影响。受全球气候变化的影响,青藏高原湖泊自20世纪90年代开始呈现剧烈扩张趋势。为揭示近年来青藏高原湖泊面积的时空变化规律,本文提出了一种改进的半自动湖泊提取算法,结合环境减灾卫星（HJ-1A/1B）和Landsat系列卫星影像数据,对青藏高原内流流域中面积大于50 km²的127个湖泊进行了连续6年的动态监测,并分析了该区域2009-2014年湖泊面积时空变化特征。研究结果表明,该区域湖泊整体呈现显著扩张趋势,年均变化速率为231.89 km²yr^-1（0.87 %yr^-1）,6年间湖泊面积扩张速率有所减缓。其中,扩张湖泊有104个,收缩湖泊有23个,变化速率分别为271.08 km²yr^-1（1.02 % yr^-1）和-39.19 km²yr^-1（-0.15 %yr^-1）。不同区域湖泊面积变化具有明显差异,主要表现为东部及北部大部分区域湖泊扩张,南部地区大部分湖泊面积稳定,萎缩湖泊主要分布于研究区四周。最后,本文通过分析冰川融水补给对湖泊面积变化的影响,发现存在冰川融水补给的湖泊面积变化率远大于不存在冰川融水补给的湖泊。由此可见,近年来冰川融水的增加是促进青藏高原内流流域湖泊扩张的主要因素之一。     

青藏高原城镇体系的时空演变

城镇体系的形成和发育对区域城镇化进程及社会经济发展起着至关重要的作用,并对生态环境产生重要影响。青藏高原特殊的地理环境与相对落后的社会经济基础,导致城镇体系不甚健全。目前国内外相关研究薄弱,不利于国家生态安全屏障建设及青藏高原可持续发展。为此,本文以建制镇以上的镇区和城市市区为研究对象,结合统计数据与遥感数据,借助GIS空间分析方法对青藏高原1990-2015年城镇体系的空间结构和规模结构进行时空演变格局分析,并采用重心移动模型揭示了青藏高原城镇人口规模和用地规模重心的迁移规律。结果表明：青藏高原城镇空间分布总体呈现出“东南密集、西北稀疏”、“大分散、小集聚”的格局;城镇分布在时间上具有阶段性增长特征且总体趋于集聚,在空间上不均衡程度呈上升趋势但2005年后明显减缓;虽然建制镇数量大幅增长,但96.88%的城镇规模在5万人以下,大中小城市发育不足;城镇人口规模重心呈现“先向西南,再向东北,又向西南”的移动轨迹;城镇用地规模重心呈现“先向东南,再向西北,再向东北”的迁移趋势。本文研究了青藏高原城镇体系的规模结构及其时空演变特征,为青藏高原新型城镇化及城镇空间格局优化提供基础依据;提出了资料缺乏和统计口径不一致的条件下城镇规模的合理估算方法,对我国城镇化相关研究具有一定的参考价值。     

青藏高原冰川变化遥感监测研究综述

在全球变暖影响下,青藏高原冰川消融造成的冰川径流增大、冰湖溃决等问题威胁着山区及其周边居民的生命财产安全,对青藏高原冰川变化的研究日益紧迫。本文综述了国内外山地冰川变化遥感监测手段的发展、冰川面积及冰面高程变化的遥感监测研究现状、存在问题与发展趋势,并总结了中国青藏高原冰川变化遥感监测研究的主要成果。此外,本文基于2003-2009年ICESat/GLAS数据,计算了青藏高原各山区冰面高程变化及其冰川消融量。结果显示：青藏高原冰川面积持续减少,青藏高原冰面高程的平均变化为-0.24±0.03 m/a,冰川融水量为-14.86±11.88 km³/a,冰川变化呈现从青藏高原东、南外缘山区往内陆与西、北部山区减慢的时空特征。     

Factors influencing the grazing management styles of settled herders: a case study of Nagqu County, Tibetan Plateau, China

The implementation of pasture contracting policies in the Tibetan Plateau has been of widespread concern in the scientific community and related government departments. Studying the effects of the implementation of pasture contracting policies will help us understand herders＇ attitudes toward those policies and to amend existing policies effectively. This paper analyzes 135 herder families＇ grazing management behavior using participatory rural appraisal （PRA）, quantitative analysis and a Logistic regression model in three townships of Nagqu County in remote areas of the Tibetan Plateau, China. The results show that the herders have become settled and are no longer nomadic, so the settlement project has basically been completed and the policy of contracting for grazing rights is being gradually implemented in Nagqu County. Since the grazing rights and pastures were under contract, group-based management has been widely accepted in this area, which helps the herders deal with constraints, such as limited pasture area, a small grazing radius, controlled family animal husbandry and an uneven distribution of water. The herders that have more family members available for labor, higher proportion of family members with good health, and higher income from animal husbandry tend to choose household-based management. Herders tend to choose group-based management when higher quality winter pastures are available.     

Rangeland privatization and its impacts on the Zoige wetlands on the Eastern Tibetan Plateau

The high Zoige Basin （Ruoergai Plateau） on the eastern Tibetan Plateau is a fault depression formed during intensive uplifting of the Tibetan Plateau. The wetland is globally important in biodiversity and is composed of marshes, bogs, fens, wet meadows and shallow water interspersed with low hills and sub-alpine meadows. Most of the Zoige wetlands have long been one of the most important grazing lands in China. Recent rangeland policy has allowed grazing, and usable wetland areas have been being legally allocated to individuals or groups of households on a long-term lease basis. Privatizafion of the wetland has impacted the Zoige wetlands in aspects of hydrologic condition, landscape and biodiversity. The uneven spatial distribution of water resources onprivatelands has led to the practice of extracting ground water, which has decreased the perched water table in Zoige. Fencing off the rangelands and grazing on expanding sand dunes have affected landscapes. Variation in the water table has led to the changes in vegetation diversity, resulting in the changes in wildlife and aquatic diversities and ecosystem processes. Making use all year round of the pasture that was previously grazed only in summer has shrunk the daily activity space of wildlife, and the newly erected fences blocked the movement of wild animals looking for food in the snow to lower and open areas. To maintain the favorable conditions of the Zoige wetland ecosystem, the author suggests that, in addition to biophysical research and implementation of conservation practices, there is an immediate need to initiate an integrated management program, increase public awareness of wetland functions and provide better training for the local conservation staff.     

Geochemistry and tectonic significance of volcanic rocks from Qushenla Formation in Gerze area of northern Tibetan Plateau

By using petrological,isotope chronological,and geochemical methods,the authors studied the volcanic rocks in the studied area,mainly including dacites and trachytes. The results show that they formed during the late Early Cretaceous. Geochemically,the volcanic rocks are relatively enriched in large-ion lithophile elements( Rb,K,and Th) and depleted in high field strength elements( Nb,Ta,and Ti),and rich in light rare earth elements,and depleted in heavy rare earth elements. The fact indicates that the main body of the volcanic rocks in the Qushenla Formation was derived from the partial melting of lower crust. The lithological assemblages are characterized by continental high-K calc-alkaline and shoshonitic series,suggesting that the southward-subducting oceanic slab in southern Bangong Lake had break off and that the Bangong Lake-Nujiang Ocean had closed before 107 Ma. The main dynamic mechanisms for the genesis of this set of intermediate-acidic volcanic rocks were upwelling of the asthenosphere and partial melting of the lower crust caused by slab break-off.