Response of Plant Growth and Biomass Accumulation to Short-term Experimental Warming in a Highland Barley System of the Tibet

Highland barley is an important staple food in the Tibet, and the Tibetan Plateau is experiencing obvious climatic warming. However, few studies have examined the warming effects on highland barley growth and biomass allocation under conditions of controlled experimental warming. This limits our ability to predict how highland barley will change as the climate changes in the future. An experiment of field warming at two magnitudes was performed in a highland barley system of the Tibet beginning in late May, 2014. Infrared heaters were used to increase soil temperature. At the end of the warming experiment (September 14, 2014), plant growth parameters (plant height, basal diameter, shoot length and leaf number), biomass accumulation parameters (total biomass, root biomass, stem biomass, leaf biomass and spike biomass), and carbon and nitrogen concentration parameters (carbon concentration, nitrogen concentration, the ratio of carbon to nitrogen concentration in root, stem, leaf and spike) were sampled. The low- and high-level experimental warming significantly increased soil temperature by 1.52 and 1.98 °C, respectively. Average soil moisture was significantly decreased by 0.03 m³ m^-3 under the high-level experimental warming, while soil moisture under the low-level experimental warming did not significantly change. The low- and high-level experimental warming did not significantly affect plant growth parameters, biomass accumulation parameters, and carbon and nitrogen concentration parameters. There were also no significant differences of plant growth parameters, biomass accumulation parameters, and carbon and nitrogen concentration parameters between the low- and high-level experimental warming. Our findings suggest that the response of highland barley growth, total and component biomass accumulation, and carbon and nitrogen concentration to warming did not linearly change with warming magnitude in the Tibet.     

Declining Precipitation Enhances the Effect of Warming on Phenological Variation in a Semiarid Tibetan Meadow Steppe

Vegetation phenology is a sensitive indicator of global warming, especially on the Tibetan Plateau. However, whether climate warming has enhanced the advance of grassland phenology since 2000 remains debated and little is known about the warming effect on semiarid grassland phenology and interactions with early growing season precipitation. In this study, we extracted phenological changes from average NDVI in the growing season (GNDVI) to analyze the relationship between changes in NDVI, phenology and climate in the Northern Tibetan Damxung grassland from 2000 to 2014. The GNDVI of the grassland declined. Interannual variation of GNDVI was mainly affected by mean temperature from late May to July and precipitation from April to August. The length of the growing season was significantly shortened due to a delay in the beginning of the growing season and no advancement of the end of the growing season, largely caused by climate warming and enhanced by decreasing precipitation in spring. Water availability was the major determinant of grass growth in the study area. Warming increased demand for water when the growth limitation of temperature to grass was exceeded in the growing season. Decreased precipitation likely further exacerbated the effect of warming on vegetation phenology in recent decades due to increasing evapotranspiration and water limitations. The comprehensive effects of global warming and decreasing precipitation may delay the phenological responses of semiarid alpine grasslands.     

1960—2019年西北地区气候变化中的Hiatus现象及特征

1998—2012年全球地表平均温度发生变暖停滞（Hiatus）,然而Hiatus现象是否在全球各地均存在尚有争议,其在西北地区的表现及特征缺乏深入研究。本文基于1960—2019年气温地面观测数据,利用累积距平曲线、Mann-Kendall突变检验、滑动t检验及Yamamoto检验进行气候突变分析,结合线性倾向估计进行气候变化趋势分析,对西北地区气候变化中的Hiatus现象及其特征进行了探讨。结果表明：① 西北地区年均气温在1986年、1996年和2012年分别突变,1996年突变升温后在1998—2012年间保持高位震荡;② 1998—2012年间西北地区年均温变化率为-0.20 ℃/10a,呈现明显Hiatus现象,分季节看,冬季降温幅度最大,夏季仍保持升温,春季均温比秋、冬季提前1年开始和结束停滞期,从空间上看,西北地区东南部降温最显著,青藏高原不存在Hiatus;③ 2012年Hiatus结束后西北地区气温普遍快速升高,季节上以冬季升温最快,空间上以南疆升温最快。综合来看,1998—2012年的Hiatus现象在除青藏高原外的西北地区表现明显,停滞后的快速升温值得高度关注。     

青藏高原"一江两河"农区居民食物消费结构与特征

居民食物消费受自然地理环境、城镇化等因素影响,同时通过市场机制影响区域粮食安全和农牧业发展。以西藏“一江两河”地区为例,基于分层抽样,通过2019年实地入户调研,获取了262户农村居民上年度食物消费数据,对青藏高原农区居民的食物消费结构及其影响因素进行分析。结果表明：① 样本内居民的植物性食物的消费量是动物性食物的3.19倍,植物性食物以蔬菜和粮食为主,动物性食物以肉类和牛奶为主;青稞及青稞酒在藏民饮食中占有重要地位。② 居民食物消费规模和结构与食物自给率指标密切相关,自给自足特征显著。③ 不同地区、家庭规模、务工规模、收入水平以及家庭年龄之间,居民的家庭食物消费结构均有所差异,且不同家庭之间面粉和水果的消费差异最显著。④ 区域差异、家庭规模类型和家庭务工规模是影响样本农区居民食物消费综合差异的主要因素。结果可为青藏高原地区居民食物消费结构改善、膳食营养提升以及农牧业转型发展提供科学基础和决策借鉴。     

Response of Plant Community Carbon and Nitrogen Stoichiometry to Experimental Warming on the Qinghai-Tibet Plateau

Low temperature is an important limiting factor for alpine ecosystems on the Tibetan Plateau. This study is based on data from on-site experimental warming platforms (open top chambers, OTC) at three elevations (4300 m, 4500 m, 4700 m) on the Qinghai-Tibet Plateau. The carbon and nitrogen stoichiometry characteristics of plant communities, both above-ground and below-ground, were observed in three alpine meadow ecosystems in August and September of 2011 and August of 2012. Experimental warming significantly increased above-ground nitrogen content by 21.4% in September 2011 at 4500 m, and reduced above-ground carbon content by 3.9% in August 2012 at 4300 m. Experimental warming significantly increased below-ground carbon content by 5.5% in August 2011 at 4500 m, and the below-ground ratio of carbon to nitrogen by 28.0% in September 2011 at 4300 m, but reduced below-ground nitrogen content by 15.7% in September 2011 at 4700 m, below-ground carbon content by 34.3% in August 2012 at 4700 m, and the below-ground ratio of carbon to nitrogen by 37.9% in August 2012 at 4700 m. Experimental warming had no significant effect on the characteristics of community carbon and nitrogen stoichiometry under other conditions. Therefore, experimental warming had inconsistent effects on the carbon and nitrogen stoichiometry of plant communities at different elevations and during different months. Soil ammonium nitrogen and nitrate nitrogen content were the main factors affecting plant community carbon and nitrogen stoichiometry.     

中国近30年气候要素时空变化特征

利用1971~2000年中国603个气象站点逐日平均温度和降水量数据,借助ArcGIS空间分析工具,采用自组织特征映射模型(SOFM),对中国气候变化的时空特征进行分析。研究结果表明:近30年中国气候变化的总体特征以增温为主,增温增湿的地区面积最为广大;季节变化构型也以增温增湿为主,秋季略有异常;从年代际变化来看,1971~1980年间,中国的气候以降温为主,而从1981年开始的20年间,全国的气候变化转为增温占主导。SOFM网络分类结果可以描述为缓增温少降水、剧增温平降水、缓增温缓降水和剧增温剧降水等四种类型。     

Response of Microbial Communities in Soil to Multi-level Warming in a Highland Barley System of the Lhasa River

No studies have examined the effect of experimental warming on the microbial biomass and community composition of soil in agricultural ecosystem on the Qinghai-Tibet Plateau. Thus it is unclear whether the influences of experimental warming on microbial communities in soil are related to warming magnitude in croplands on this Plateau. This study performed warming experiment (control, low- and high-level) in a highland barley system of the Lhasa River in May 2014 to examine the correlation between the response of microbial communities in soil to warming and warming magnitude. Topsoil samples (0-10 and 10-20 cm) were collected on September 14, 2014. Experimental warming at both low and high levels significantly increased soil temperature by 1.02 ℃ and 1.59 ℃, respectively at the depth of 15 cm. Phospho lipid fatty acid (PLFA) method was used to determine the microbial community in soil. The low-level experimental warming did not significantly affect the soil’s total PLFA, fungi, bacteria, arbuscular mycorrhizal fungi (AMF), actinomycetes, gram-positive bacteria (G⁺), gram-negative bacteria (G^-), protozoa, the ratio of fungi to bacteria (F/B ratio), and ratio of G⁺ to G^- (G⁺/G^- ratio) at the 0-10 and 10-20 cm depth. The low-level experimental warming also did not significantly alter the composition of microbial community in soil at the 0-10 and 10-20 cm depth. The high-level experimental warming significantly increased total PLFA by 74.4%, fungi by 78.0%, bacteria by 74.0%, AMF by 66.9%, actinomycetes by 81.4%, G⁺ by 67.0% and G^- by 74.4% at the 0-10 cm depth rather than at 10-20 cm depth. The high-level experimental warming significantly altered microbial community composition in soil at the 0-10 cm depth rather than at 10-20 cm depth. Our findings suggest that the response of microbial communities in soil to warming varied with warming magnitudes in the highland barley system of the Lhasa River.     

Changes in air temperature over China in response to the recent global warming hiatus

The 1998-2012 global warming hiatus has aroused great public interest over the past several years. Based on the air temperature measurements from 622 meteorological stations in China, the temperature response to the global warming hiatus was analyzed at national and regional scales. We found that air temperature changed -0.221℃/10a during 1998-2012, which was lower than the long-term trend for 1960-1998 by 0.427℃/10a. Therefore, the warming hiatus in China was more pronounced than the global mean. Winter played a dominant role in the nationwide warming hiatus, contributing 74.13%, while summer contributed the least among the four seasons. Furthermore, the warming hiatus was spatial heterogeneous across different climate conditions in China. Comparing the three geographic zones, the monsoon region of eastern China, arid region of northwestern China, and high frigid region of the Tibetan Plateau, there was significant cooling in eastern and northwestern China. In eastern China, which contributed 53.79%, the trend magnitudes were 0.896℃/10a in winter and 0.134℃/10a in summer. In the Tibetan Plateau, air temperature increased by 0.204℃/10a, indicating a lack of a significant warming hiatus. More broadly, the warming hiatus in China may have been associated with the negative phase of PDO and reduction in sunspot numbers and total solar radiation. Finally, although a warming hiatus occurred in China from 1998 to 2012, air temperature rapidly increased after 2012 and will likely to continuously warm in the next few years.     

中国气温变化对全球变暖停滞的响应

1998-2012年出现的全球变暖停滞（global warming hiatus）现象,近年来受到各界的广泛关注。基于中国622个气象站的气温数据,研究了全国及三大自然区气温变化对全球变暖停滞的响应。结果表明：① 1998-2012年间,中国气温变化率为-0.221 ℃/10 a,较1960-1998年增温率下降0.427 ℃/10 a,存在同全球变暖停滞类似的增温减缓现象,且减缓程度更明显,其中冬季对中国增温减缓的贡献最大,贡献率为74.13%,夏季最小;② 中国气温变化对全球变暖停滞的响应存在显著的区域差异,从不同自然区看,1998-2012年东部季风区和西北干旱区降温显著,其中东部季风区为中国最强降温区,为全国增温减缓贡献了53.79%,并且具有显著的季节依赖性,减缓期冬季气温下降了0.896 ℃/10 a,而夏季上升了0.134 ℃/10 a。青藏高寒区1998-2012年增温率达0.204 ℃/10 a,对全球变暖停滞的响应并不显著;③ 中国增温减缓可能受太平洋年代际振荡（PDO）负相位、太阳黑子数与太阳总辐照减小等因素的影响;④ 1998-2012年中国虽出现增温减缓现象,但2012年之后气温快速升高,且从周期变化看,未来几年可能持续升温。     

雅鲁藏布江流域1961-2005年气候变化趋势

The Yarlung Zangbo River (YR) is the highest great river in the world, and its basin is one of the centers of human economic activity in Tibet. Using 10 meteorological stations over the YR basin in 1961–2005, the spatial and temporal characteristics of temperature and precipitation as well as potential evapotranspiration are analyzed. The results are as follows. (1) The annual and four seasonal mean air temperature shows statistically significant increasing trend, the tendency is more significant in winter and fall. The warming in Lhasa river basin is most significant. (2) The precipitation is decreasing from the 1960s to the 1980s and increasing since the 1980s. From 1961 to 2005, the annual and four seasonal mean precipitation is increasing but not statistically significant, especially in fall and spring. The increasing precipitation rates are more pronounced in Niyangqu and Palong Zangbo river basins, the closer to the upper YR is, the less precipitation increasing rate would be. (3) The annual and four seasonal mean potential evapotranspiration has decreased, especially after the 1980s, and most of it happens in winter and spring. The decreasing trend is most significant in the middle YR and Nianchu river basin. (4) Compared with the Mt. Qomolangma region, Tibetan Plateau, China and global average, the magnitudes of warming trend over the YR basin since the 1970s exceed those areas in the same period, and compared with the Tibetan Plateau, the magnitudes of precipitation increasing and potential evapotranspiration decreasing are larger, suggesting that the YR basin is one of the most sensitive areas to global warming.     

Climate change over the Yarlung Zangbo River Basin during 1961–2005

The Yarlung Zangbo River (YR) is the highest great river in the world, and its basin is one of the centers of human economic activity in Tibet. Using 10 meteorological stations over the YR basin in 1961–2005, the spatial and temporal characteristics of temperature and precipitation as well as potential evapotranspiration are analyzed. The results are as follows. (1) The annual and four seasonal mean air temperature shows statistically significant in-creasing trend, the tendency is more significant in winter and fall. The warming in Lhasa river basin is most significant. (2) The precipitation is decreasing from the 1960s to the 1980s and increasing since the 1980s. From 1961 to 2005, the annual and four seasonal mean precipi-tation is increasing but not statistically significant, especially in fall and spring. The increasing precipitation rates are more pronounced in Niyangqu and Palong Zangbo river basins, the closer to the upper YR is, the less precipitation increasing rate would be. (3) The annual and four seasonal mean potential evapotranspiration has decreased, especially after the 1980s, and most of it happens in winter and spring. The decreasing trend is most significant in the middle YR and Nianchu river basin. (4) Compared with the Mt. Qomolangma region, Tibetan Plateau, China and global average, the magnitudes of warming trend over the YR basin since the 1970s exceed those areas in the same period, and compared with the Tibetan Plateau, the magnitudes of precipitation increasing and potential evapotranspiration decreasing are larger, suggesting that the YR basin is one of the most sensitive areas to global warming.     

Two centuries of temperature variation and volcanic forcing reconstructed for the northern Tibetan Plateau

Abstract

The northern Tibetan Plateau has been subject to recent warming far above the global average. With few instrumental climate records available for this region before the 1950s, paleoclimatic reconstructions must be used to understand annual-to-centennial-scale climate variations and local climate response to large-scale forcing mechanisms. We developed a maximum latewood density chronology of Qinghai spruce (Picea crassifolia) from the southern slope of the Qilian Mountains, northern Tibetan Plateau. Based on the chronology, we reconstructed August–September temperature for 1780–2008. The temperature reconstruction model accounts for 39.7% of instrumental temperature variance from 1957 to 2008, successfully capturing the most recent warming. Superposed epoch analysis indicated a volcanic forcing for temperature, resulting in pulses of cooler conditions that can persist for 2–4 years. Tree-ring data indicated that warm-dry and cold-wet climate combinations mainly occurred in northern Tibetan Plateau before CE 1900, and revealed a clear wetting and warming trend since the 1980s. Our study provides long-term perspective on recent climate change in northern Tibetan Plateau to guide expectations of future climate variability and aid sustainable development, and provides scenarios for climate change adaptation and inputs for climate models representing a broader range of conditions than those of historical climate records.     

近50年来中国冬季风寒温度的变化

风寒温度是冬季表征人体热舒适度常用的参数,也是气候变化影响研究中关注的要素。本文利用中国地面国际交换站气候资料月值数据集的气温和风速,分析1956-2005年中国冬季风寒温度的时间和空间变化特征。结果表明,近50年来中国冬季风寒温度普遍呈上升趋势,全国平均升高3.2 ^oC,变化速率达0.64 ^oC/10a;西北、华北、东北和青藏地区的上升速率分别为0.79 ^oC/10a、0.84 ^oC/10a、0.81 ^oC/10a、0.80 ^oC/10a,其中华北北部农牧交错带地区上升趋势最为强烈,超过1 ^oC/10a;35^oN以南的我国南方地区上升速率较低,为0.39 ^oC/10a。风寒温度的这种变化特征是近50年来气温升高和风速下降综合作用的结果。其中气温变化造成的风寒温度上升是2.4 ^oC,而地表风速下降对风寒温度的贡献为0.8 ^oC。东亚气温和风速的变化受诸多大气环流系统的影响,分析表明影响东亚气候的几个主要环流因子中,西伯利亚高压、北极涛动、西太平洋遥相关型和欧亚遥相关型等与风寒温度有显著相关。这四个环流因子一起能解释50年来全国平均风寒温度方差的46.7%。全国平均气温与这四个环流因子的相关分别达到-0.65,+0.49,+0.31和-0.32;而平均风速与北极涛动的相关最显著,达-0.51。     

Investigating changes in lake systems in the south-central Tibetan Plateau with multi-source remote sensing

Lakes in the Tibetan Plateau are considered sensitive responders to global warming. Variations in physical features of lake systems such as surface area and water level are very helpful in understanding regional responses to global warming in recent decades. In this study, multi-source remote sensing data were used to retrieve the surface area and water level time series of five inland lakes in the south-central part of the Tibetan Plateau over the past decades. Changes in water level and surface area of the lakes were investigated. The results showed that the water level of three lakes (Puma Yumco, Taro Co, Zhari Namco) increased, with expanding surface area, while the water levels of the other two lakes (Paiku Co, Mapam Yumco) fell, with shrinking area. The water levels of the lakes experienced remarkable changes in 2000–2012 as compared with 1976–1999. Spatially, lakes located at the southern fringe of the Tibetan Plateau showed consistency in water level changes, which was different from lakes in the central Tibetan Plateau.     

Interdecadal correlation of solar activity with Tibetan Plateau snow depth and winter atmospheric circulation in East Asia

Studies on the impact of solar activity on climate system are very important in understanding global climate change. Previous studies in this field were mostly focus on temperature, wind and geopotential height. In this paper, interdecadal correlations of solar activity with Winter Snow Depth Index (WSDI) over the Tibetan Plateau, Arctic Oscillation Index (AOI) and the East Asian Winter Monsoon Index (EAWMI) are detected respectively by using Solar Radio Flux (SRF), Total Solar Irradiance (TSI) and Solar Sunspot Number (SSN) data and statistical methods. Arctic Oscillation and East Asian winter monsoon are typical modes of the East Asian atmospheric circulation. Research results show that on interdecadal time scale over 11-year solar cycle, the sun modulated changes of winter snow depth over the Tibetan Plateau and East Asian atmospheric circulation. At the fourth lag year, the correlation coefficient of SRF and snow depth is 0.8013 at 0.05 significance level by Monte-Carlo test method. Our study also shows that winter snow depth over the Tibetan Plateau has significant lead and lag correlations with Arctic Oscillation and the East Asian winter monsoon on long time scale. With more snow in winter, the phase of Arctic Oscillation is positive, and East Asian winter monsoon is weak, while with less snow, the parameters are reversed. An example is the winter of 2012/2013, with decreased Tibetan Plateau snow, phase of Arctic Oscillation was negative, and East Asian winter monsoon was strong.     

The Effect of Higher Warming on Vegetation Indices and Biomass Production is Dampened by Greater Drying in an Alpine Meadow on the Northern Tibetan Plateau

In order to understand whether or not the response of vegetation indices and biomass production to warming varies with warming magnitude, an experiment of field warming at two magnitudes was conducted in an alpine meadow on the northern Tibetan Plateau beginning in late June, 2013. The normalized difference vegetation index (NDVI), green normalized difference vegetation index (GNDVI) and soil adjusted vegetation index (SAVI) data were obtained using a Tetracam Agricultural Digital Camera in 2013-2014. The gross primary production (GPP) and aboveground plant biomass (AGB) were modeled using the surface measured NDVI and climatic data during the growing seasons (i.e. June-September) in 2013-2014. Both low and high warming significantly increased air temperature by 1.54 and 4.00°C, respectively, and significantly increased vapor pressure deficit by 0.13 and 0.31 kPa, respectively, in 2013-2014. There were no significant differences of GNDVI, AGB and ANPP among the three warming treatments. The high warming significantly reduced average NDVI by 23.3% (-0.06), while the low warming did not affect average NDVI. The low and high warming significantly decreased average SAVI by 19.0% (-0.04) and 27.4% (-0.05), respectively, and average GPP by 24.2% (i.e. 0.21 g C m^-2 d^-1) and 44.0% (i.e. 0.39 g C m^-2 d^-1), respectively. However, the differences of the average NDVI, SAVI, and GPP between low and high warming were negligible. Our findings suggest that a greater drying may dampen the effect of a higher warming on vegetation indices and biomass production in alpine meadow on the northern Tibetan Plateau.     

Simulated effect of soil freeze-thaw process on surface hydrologic and thermal fluxes in frozen ground region of the Northern Hemisphere

Soil freeze-thaw process is closely related to surface energy budget,hydrological activity,and terrestrial ecosystems.In this study,two numerical experiments(including and excluding soil freeze-thaw process)were designed to examine the effect of soil freeze-thaw process on surface hydrologic and thermal fluxes in frozen ground region in the Northern Hemisphere based on the state-of-the-art Community Earth System Model version 1.0.5.Results show that in response to soil freeze-thaw process,the area averaged soil temperature in the shallow layer(0.0175?0.0451 m)decreases by 0.35℃in the TP(Tibetan Plateau),0.69℃in CES(Central and Eastern Siberia),and 0.6℃in NA(North America)during summer,and increases by 1.93℃in the TP,2.28℃in CES and 1.61℃in NA during winter,respectively.Meanwhile,in response to soil freeze-thaw process,the area averaged soil liquid water content increases in summer and decrease in winter.For surface heat flux components,the ground heat flux is most significantly affected by the freeze-thaw process in both summer and winter,followed by sensible heat flux and latent heat flux in summer.In the TP area,the ground heat flux increases by 2.82 W/m2(28.5%)in summer and decreases by 3.63 W/m2(40%)in winter.Meanwhile,in CES,the ground heat flux increases by 1.89 W/m2(11.3%)in summer and decreases by 1.41 W/m2(18.6%)in winter.The heat fluxes in the Tibetan Plateau are more susceptible to the freeze-thaw process compared with the high-latitude frozen soil regions.Soil freeze-thaw process can induce significant warming in the Tibetan Plateau in winter.Also,this process induces significant cooling in high-latitude regions in summer.The frozen ground can prevent soil liquid water from infiltrating to deep soil layers at the beginning of thawing;however,as the frozen ground thaws continuously,the infiltration of the liquid water increases and the deep soil can store water like a sponge,accompanied by decreasing surface runoff.The influence of the soil freeze-thaw process on surface hydrologic and thermal fluxes varies seasonally and spatially.     

Ground temperature variation and its response to climate change on the northern Tibetan Plateau

Ground temperature plays a significant role in the interaction between the land surface and atmosphere on the Tibetan Plateau(TP). Under the background of temperature warming, the TP has witnessed an accelerated warming trend in frozen ground temperature, an increasing active layer thickness, and the melting of underground ice. Based on high-resolution ground temperature data observed from 1997 to 2012 on the northern TP, the trend of ground temperature at each observation site and its response to climate change were analyzed. The results showed that while the ground temperature at different soil depths showed a strong warming trend over the observation period, the warming in winter is more significant than that in summer. The warming rate of daily minimum ground temperature was greater than that of daily maximum ground temperature at the TTH and MS3608 sites. During the study period, thawing occurred earlier, whereas freezing happened later, resulting in shortened freezing season and a thinner frozen layer at the BJ site. And a zero-curtain effect develops when the soil begins to thaw or freeze in spring and autumn. From 1997 to 2012, the average summer air temperature and precipitation in summer and winter from six meteorological stations along the Qinghai-Tibet highway also demonstrated an increasing trend, with a more significant temperature increase in winter than in summer. The ground temperature showed an obvious response to air temperature warming, but the trend varied significantly with soil depths due to soil heterogeneity.     

青藏高原近40年来的降水变化特征

利用我国青藏高原地区的1961-2000年56个气象站的逐月降水资料,通过计算降水量的距平百分率,分析了青藏高原自1961至2000年以来降水量变化的趋势和1961-2000年以来各季降水量变化趋势,发现:青藏高原近40年来降水量呈增加趋势,降水量的线性增长率约为1.12mm/a。再将高原划分为四个季节,分析了各季40年来的降水量的变化情况得出:春季降水量年际变化较大,秋季降水量变化不明显。夏季降水量值较大而降水变化幅度较小,冬季降水量变化则与夏季相反。通过将青藏高原分为南北两个地区,分析了两个区的年降水量和四个季节的降水量的变化得出:高原南区1961-2000年降水量呈增加的趋势,降水量的线增长率为1.97 mm/a,春季和冬季降水量年际变化较大,夏季降水量变化不明显,秋季降水量略有增加;北区年降水量和夏季的降水量变化较小,秋季降水量的年际变化较大,冬季降水量变化最大。对青藏高原的南北两区用Mann-Kendall方法进行突变分析,显示高原南区分别在1978年和1994年发生突变,北区没有发现突变。     

2009-2015年国际青藏高原研究文献计量分析——基于SCIE和ESI数据

青藏高原及其周边地区以独特的自然地理环境和复杂的地质构造,及其对全球环境和气候变化不可忽视的影响,长期以来一直受到国际科学家的关注。本文以SCIE和ESI数据库为数据源,检索2009-2015年间上述数据库报道的青藏高原及其周边地区研究文献及其引用情况,通过文献计量方法,采用多种分析工具,从多个角度对青藏高原及其周边地区研究现状与进展情况进行分析,在此基础上总结近年来国际青藏高原领域的研究态势,主要结论为：整体上近年来国际青藏高原领域研究规模和学术影响力呈现良好发展态势;研究实力上,中国、印度、美国仍稳居国家论文产出前三位,但青藏高原周边国家如巴基斯坦、尼泊尔发展较快,在机构层面上中国机构的整体优势逐渐扩大。中国的青藏高原研究呈现出量、质齐升的发展态势;青藏高原的发文期刊仍以地学、环境类期刊为主,高被引论文主要发表在高质量的综合类期刊上。青藏高原的研究学科持续完备,研究内容地域特色明显,研究主题包括青藏高原的隆升机制、高原各个圈层对全球气候变化的影响、高寒生态系统的生物多样性及对全球变暖的响应等。今后,中国青藏高原研究应着力聚焦前沿科学问题,促进多学科交叉融合,提升协同化集成化自主科研创新能力,产出具有国际影响力的重大科学成果,为“一带一路”战略实施和区域生态环境管理提供科技支撑。