受气候变化影响,近20 a来长江源区径流条件发生了较大变化。以沱沱河为研究区域,采用沱沱河1960—2019年实测水文气象资料,分析了长江源区沱沱河季节性径流变化规律,以及季节性降水、气温的变化规律,采用交叉小波变换分析季节性径流与降水、气温之间的时频变化规律及其相关关系。研究结果表明:沱沱河春、夏、秋季径流均呈现出显著增加的趋势,其中春、夏、秋季径流突变点均集中在2006—2008年附近;各季节性降水增加的趋势并不显著,但季节性气温显著上升并延续至今;夏季径流与夏季降水之间的相关程度最为明显,其次为秋季和春季;气温对径流的影响是正相关的,但在不同时间尺度上存在不同的表征,其中以夏季气温和秋季气温对径流的影响最为显著。研究结果对揭示气候变化条件下长江源区季节性径流演变规律及其水文响应提供了参考。

Climate change has greatly impacted the runoff conditions in the source region of the Yangtze River in the past two decades. We analyzed the seasonal runoff variation, seasonal precipitation, and temperature variation based on measured hydro-meteorological data from the Tuotuo River hydrological station and meteorological station from 1960 to 2019. The cross wavelet transform is applied to examine the time-frequency variation and correlation among runoff, precipitation, and air temperature. Results reveal that the runoff of Tuotuo River in spring, summer, and autumn exhibited a significant increasing trend, with abrupt change points concentrated around 2006-2008. The increasing trend of seasonal precipitation was not significant, but the seasonal temperature displayed a marked rise that continues to the present. The correlation between summer runoff and precipitation was the most apparent, followed by autumn and spring. Temperature had a positive correlation with runoff, but it manifested differently on various time scales. Summer and autumn temperatures had the most significant effect on runoff. These findings provide important insights into the evolution law of seasonal runoff and hydrological response in the source region of the Yangtze River under the impacts of climate change.

利用NCEP/NCAR再分析资料、 AO指数序列、 全球SST资料以及全国160站月降水量资料， 分析了1951/1952-2007/2008年我国冬季降水与AO指数的相互关系及其年代际变化。结果表明, 我国冬季降水与AO的相关关系在1978/1979-1989/1990年非常显著。通过回归分析得出， 1978/1979-1989/1990年AO与500 hPa东亚大槽密切相关， 当AO偏强时， 东亚大槽偏弱， 西伯利亚高压偏弱， 冬季风偏弱， 低层我国东北地区有一异常反气旋， 异常环流西南侧偏南、 偏东风分量增强， 有利于从西北太平洋和孟加拉湾向我国中部、 东部输送水汽， 影响冬季降水。东赤道太平洋SST可能对我国冬季降水与AO关系年代际变化有影响， 当降水与AO的相关关系偏强时， 降水与SST的相关关系则偏弱； 1951/1952-1977/1978年和1990/1991-2007/2008年， SST与500 hPa副热带高压密切相关， 当SST偏高时， 副热带高压偏强， 低层我国东部沿海、 南海地区南风分量偏强， 有利于向我国东南地区输送暖湿气流， 影响东南地区冬季降水。

In this study the relationships between the Arctic Oscillation and climate in China in boreal winter are investigated. The data used in this study include NCEP/NCAR Reanalysis monthly mean sea level pressure, 500 hPa geopotential heights, two Arctic Oscillation indices, and the observed temperature and precipitation. Correlation analysis for the last 41 years shows that the winter temperature and precipitation in China change in phase with AO. High positive correlation between temperature and AO is above +0.4 and appears in the northern China. High correlation coefficients between precipitation and AO cover the southern China (close to the South China Sea) and the central China (between 30^o-40^oN and east of ~100^oE), with the values varying between +0.3 and +0.4. The correlation between the 160-station average temperature and the simultaneous sea level pressure show that the winter temperature of China is strongly connected to the sea level pressure over the high latitudes of Eurasia continent. The center is located in Siberia with values lower than -0.6. The partial correlation between the intensity of Siberian High and averaged temperature in China remains -0.58, when AO keeps constant. But the partial correlation between temperature and AO is only 0.14 when the influence of Siberian High is excluded. The relationship between AO and precipitation is also significant. The partial correlation between AO and mean precipitation of 160 stations is 0.36. But when the AO's influence is excluded, the partial correlation between the intensity of Siberian High and precipitation is only -0.16. This suggests that during the past several decades the precipitation was strongly affected by AO, but for the temperature the Siberian High plays a more important role. AO and the Siberian High correlate at -0.51, according to the data for the period 1958/59-1994/95. The possible dynamical connection between AO and the Siberian High needs further study. Using the long-term series of AO and the Siberian High spanning 1899/1900-1994/1995, their connections to climate in China are analyzed too. At the interdecadal time scale the AO shows significant influence on both temperature and precipitation. Partial correlation between AO and temperature is 0.66. For precipitation the correlation coefficient is 0.70.

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。

By using the monthly temperature, precipitation and greenhouse gases data from 88 meteorological stations in the Qinghai-Tibet Plateau from 1961 to 2012 as well as climate change scenarios data determined by CMIP5, several truth about warm and wet climate in the plateau for the 52 years are analyzed. The correlations among greenhouse gas, plateau heating field, plateau monsoon and the Arctic Oscillation (AO) index with its inter-annual oscillation are revealed. The possible climate change trend in the future 30-50 years is predicted. The results show that the warming trend has been alleviated since 2006 with a totally warming for 52 a; compared with global change, it has delayed for 8 a; precipitation has increased obviously in the plateau; climate wetting has delayed as compared with warming; 5 a short period precipitation variation has been not significant, instead of 12 a and 25 a period precipitation variation. With the greenhouse gas and aerosol increasing, plateau summer monsoon has enhanced, ENSO events and solar radiation has decreased, climate in the plateau has become warmer continuously but eased; plateau heating field has enhanced in spring and plateau summer monsoon has erupted early and kept strong, which lead to more rainfall in spring and summer, as well as the annual precipitation; yet in autumn and winter, AO has been relatively stable, east Asian trough intensity also has changed not obviously, as well as the plateau winter monsoon, as a result, precipitation in autumn and winter also has changed insignificantly. Temperature and precipitation in the plateau will be kept increasing in the future 20-40 years.

利用耦合的全球海气模式（NCAR CCSM3）， 对青藏高原春季土壤湿度异常影响我国夏季7月降水的机制进行了数值模拟。结果表明， 高原6~62 cm深度的中层土壤湿度异常与表层土壤湿度异常有很好的一致性， 相对而言， 中层土壤湿度异常的持续性较好。若5月高原中层土壤偏湿， 则春末至夏初高原地面蒸发、 潜热通量增加， 而感热通量、 地面温度降低， 高原表面的加热作用减弱， 使得印度高压西撤偏晚， 环流系统的季节性转换偏晚， 东亚地区形成有利于我国夏季出现第I类雨型的环流分布形势， 使我国东部雨带偏北， 华北地区多雨， 江淮地区降水偏少， 华南地区降水偏多; 反之亦然。

利用黄河、长江源区气象站的降水资料和NCEP/NCAR再分析气候资料,分析了黄河、长江源区降水的年际变化,对黄河、长江源区典型多雨年与少雨年的500 hPa位势高度和风场、600 hPa流场、大气水汽含量和水汽输送进行了合成和对比分析.结果表明:黄河和长江源区的降水在近50 a的长期变化趋势都不明显,但在最近10 a黄河源区的降水有明显的减少趋势.而长江源区的降水则有明显的增加趋势;江河源区在多雨与少雨年有明显的环流差异特征,在多/少雨年,500 hPa蒙古低压减弱/加强,西风风速减弱/增强,600 hPa高原辐合线偏北/南,江河源区大气水汽含量增加/减少,西南季风的偏南水汽输送增加/减少.使得江河源区有较多/少的水汽来源,从而降水增多/减少;黄河和长江源区有相似的多雨与少雨年环流差异特征,只是差异程度不同,长江源区多雨与少雨年环流特征差异的强度不及黄河源区.

On the basic of weather station precipitation data and NCEP/NCAR reanalysis data,interannual change of precipitation over the source regions of the Yellow River and the Yangtze River are respectively analyzed.Composite characteristics of the geopotential height and wind field on 500 hPa,the flow field on 600 hPa,the atmospheric water vapor content and water vapor transport for the typical rainiest and rainless years over the source regions of the Yellow River and the Yangtze River are respectively analyzed and compared.The results show that,the long-term change trend of the precipitations over the source regions of the Yellow River and the Yangtze River are not clear during the last 50 years but obvious decreased over the source regions of the Yellow River and increased over the source regions of the Yangtze River during the last 10 years.There are obvious circulation difference characteristics between rainiest and rainless years.In the rainiest/rainless year,the Mongol low pressure on 500 hPa is weaker/stronger and so the westerly speed is weaker/stronger,the Plateau convergence line on 600 hPa moves north /south,the water vapor content over the river source regions increases/decreases,the water vapor transport from south by the southwest monsoon increases/decreases and make more/less water vapor source to the river source regions and so make more/less precipitation.There are similar atmospheric circulation difference characteristics between the source regions of the Yellow River and the Yangtze River for rainiest and rainless years but the circulation difference degree is stronger over the source regions of the Yellow River than over the source regions of the Yangtze River.

近几十年来长江源区河川径流条件发生了较大变化,研究全球变暖背景下长江源区径流变化特征对于认识气候变化引起的水文效应具有重要的现实意义。利用沱沱河水文站和气象站1960—2019年实测水文气象数据,分析径流演变规律及其与降水、气温、蒸发等气象因素间的关系。采用青藏高原5根冰芯δ¹⁸O记录与冰芯积累量,分析了不同冰芯间δ¹⁸O记录、冰芯积累量之间的关系,以及冰芯记录与沱沱河径流之间的相关性。在此基础上重建沱沱河水文站1900—1960年10 a滑动平均径流系列,并初步分析100多年来沱沱河径流的丰枯变化规律。研究结果表明,沱沱河水文站年径流在2002年前后发生显著增加的趋势,长江源区气温急剧上升导致的冰川和积雪融水增多是长江源区流量急剧增加的重要原因之一。重建沱沱河1900年以来径流系列表明,长江源区经历了多次的丰枯交替变化,径流变化规律与青藏高原3次气候突变时间点基本吻合。研究结果对揭示气候变化条件下长江源区河川径流演变规律及其水文响应提供了参考。

Runoff in the source region of the Yangtze River has undergone great changes in recent decades.It is of great practical significance to study the characteristics of runoff variation under the background of global warming for understanding the hydrological effects caused by climate change.The evolution of runoff and its relationship with meteorological factors such as precipitation, temperature, and evaporation were analyzed based on measured hydro-meteorological data from 1960 to 2019 at Tuotuo River.The relationship between δ¹⁸O records and ice core accumulations among different ice cores, and the correlation between ice core records and runoff in Tuotuo River were examined.The 10-year moving average runoff series of the Tuotuo River from 1900 to 1960 was reconstructed, and the runoff variation of Tuotuo River over the past century was analyzed.Results revealed a siginificant increase trend of annual runoff of Tuotuo River around 2002.The increase in glaciers and snow melt induced by the sharp rise in temperature is an important cause for the sharp increase in flow rate in the source region of the Yangtze River.The reconstruction of the runoff series of Tuotuo River since 1900 demonstrated that the source area of the Yangtze River had experienced many alternating dry-wet changes, and the runoff variation rules are in general consistent with the three abrupt climate changes in the Tibetan Plateau.The research findings provided a basis for revealing the evolution law and hydrological response of river runoff in the source region of the Yangtze River under climate change.