Snow cover is critical to the ground thermal regime because it affects surface conditions and the energy balance. Prior work inherently included confounding effects from vegetation and the soil when estimating the snow’s effect by using the differences between air and ground surface or soil temperature. Here we use the Kudryavtsev model including a snow module to isolate the effect of only the snow cover during winter, based on observational sites across the Northern Hemisphere. We find that snow’s damping of annual mean ground surface temperature averages 5.06 ± 3.15 °C and ranges 0 °C–10 °C, while damping of the annual ground surface temperature amplitude is 7.95 ± 4.95 °C, ranging 0 °C–20 °C. Greater insulation occurs in the high-latitudes. The insulating effect is primarily driven by snow depth, but also the combination of air temperature and its amplitude, snow depth, and duration. Snow cover duration and low air temperature enhance snow’s insulating ability. These observational results that isolate the damping effect of only the snow could play a significant role in better understanding the energy change between air and the ground.

积雪作为冰冻圈的重要组成， 是地球系统中不可或缺的部分， 也是全球气候变化的“指示器”。积雪对气候系统的影响主要源于其高反照率和低导热率等物理特性。由于气候系统对地表反照率的变化十分敏感， 地表反照率的微小变化会显著影响气候系统的能量平衡， 进而通过积雪反照率反馈作用快速影响高原及其下游地区的大气条件。鉴于青藏高原积雪较薄， 且具有反复积累和消融的特征， 本文旨在深入研究积雪有无条件下青藏高原土壤水热过程及地表能量通量的变化特征。本文基于日尺度数据， 通过设定反照率大于0.5的判据， 探讨不同下垫面类型下积雪对地表微气象特征的影响。研究结果表明青藏高原多年平均地表反照率为0.22， 且呈现“西北高、 东南低”的空间分布特征和“冬春高， 夏秋低”的季节变化模态。青藏高原地表反照率受积雪的影响， 区域和季节性差异显著。终年积雪区的面积较小， 仅占总面积的0.55%。选取位于不同气候区的那曲站、 纳木错站和垭口站地表存在积雪覆盖和无积雪条件下的土壤水热特征及地表能量通量特征进行分析， 主要结论如下： （1）在有积雪存在时， 正午时段的地表反照率通常超过0.6， 而在无积雪条件下， 正午时反照率通常低于0.3； （2）在积雪存在的情况下， 土壤水热协同作用较为稳定。具体而言， 在那曲站， 尽管积雪存在状态不稳定， 保温效应较弱， 但积雪的存在可以减小土壤温度的波动。纳木错站和垭口站的积雪状态稳定， 保温效果较为明显， 与无积雪条件下相比， 土壤温度和土壤含水量较高， 且变化幅度较小， 土壤冻结深度较浅； （3）在积雪覆盖情况下， 地表能量的闭合率较低， 湍流通量与有效能量之间的相关性较强。由于那曲站和垭口站不同的积雪条件， 两个站点在地表能量分配方面有明显差异。无论有无积雪覆盖， 那曲站净辐射主要分配给感热通量， 但较浅的积雪覆盖使潜热通量占比增加； 垭口站积雪连续， 有积雪覆盖时净辐射主要分配给潜热通量， 无积雪覆盖时净辐射主要分配给感热通量； 在有积雪覆盖时， 下垫面湿润， 波文比大都在1.0以下， 而在无积雪覆盖时， 波文比较大； （4）冬季， 当有积雪覆盖时， 积雪的保温作用使得土壤温度高于大气温度， 土壤热通量主要向大气传递。随着积雪的逐渐融化， 地表接收到的能量逐渐增加。

As an important component of the cryosphere， snow cover is an indispensable part of the Earth's system and also an "indicator" of global climate change.The impact of snow cover on the climate system mainly originates from its physical properties such as high albedo and low thermal conductivity.Since the climate system is highly sensitive to changes in surface albedo， slight variations in surface albedo can significantly affect the energy balance of the climate system， thereby rapidly influencing the atmospheric conditions on the Qinghai-Xizang Plateau （QXP） and its downstream areas through the snow albedo feedback mechanism.Given that snow cover on the QXP is relatively thin and characterized by repeated accumulation and ablation， this paper aims to conduct an in-depth study on the variation characteristics of soil hydrothermal processes and surface energy fluxes on the QXP under snow-covered and snow-free conditions.Based on daily-scale data， this study explores the impact of snow cover on surface micrometeorological characteristics under different underlying surface types by setting a criterion that albedo is greater than 0.5.The research results show that the multi-year average surface albedo of the QXP is 0.22， exhibiting a spatial distribution characteristic of "high in the northwest and low in the southeast" and a seasonal variation pattern of "high in winter and spring， low in summer and autumn".The surface albedo of the QXP is affected by snow cover， with significant regional and seasonal differences.The area of perennial snow cover is small， accounting for only 0.55% of the total area.This paper selects Naqu Station， Namors Station， and Yakou Station located in different climate zones to analyze the soil hydrothermal characteristics and surface energy flux characteristics under snow-covered and snow-free conditions.The main conclusions are as follows： （1） When snow cover exists， the surface albedo at noon usually exceeds 0.6， while under snow-free conditions， the albedo at noon is usually lower than 0.3； （2） When snow cover exists， the soil hydrothermal synergistic effect is relatively stable.Specifically， at Naqu Station， although the snow cover state is unstable and the heat preservation effect is weak， the presence of snow cover can reduce the fluctuation of soil temperature.The snow cover states at Namors Station and Yakou Station are stable， and the heat preservation effect is more obvious.Compared with the snow-free conditions， the soil temperature and soil water content are higher， the variation range is smaller， and the soil freezing depth is shallower； （3） Under snow-covered conditions， the closure rate of surface energy is low， and the correlation between turbulent flux and effective energy is strong.Due to the different snow cover conditions at Naqu Station and Yakou Station， there are obvious differences in surface energy distribution between the two stations.Regardless of snow cover， the net radiation at Naqu Station is mainly allocated to sensible heat flux， but shallow snow cover increases the proportion of latent heat flux； at Yakou Station， snow cover is continuous.When there is snow cover， net radiation is mainly allocated to latent heat flux， and when there is no snow cover， net radiation is mainly allocated to sensible heat flux； when there is snow cover， the underlying surface is wet， and the Bowen ratio is mostly below 1.0， while when there is no snow cover， the Bowen ratio is larger； （4） In winter， when there is snow cover， the heat preservation effect of snow cover makes the soil temperature higher than the atmospheric temperature， and the soil heat flux is mainly transmitted to the atmosphere.As the snow gradually melts， the energy received by the surface gradually increases.

融雪水是澜沧江流域春季径流的重要组成部分,掌握澜沧江上游积雪变化规律,准确模拟融雪径流过程,对澜沧江流域梯级水电站水资源科学调度具有重要意义。基于2000—2019年卫星遥感积雪覆盖率数据,采用Mann-Kendall趋势检验法分析了澜沧江上游积雪覆盖率的时空变化规律,构建了融雪径流模型(SRM),模拟了澜沧江上游2008—2018年融雪期径流过程,并基于粒子群优化(PSO)算法开展了参数率定。结果表明:①澜沧江上游积雪覆盖率在春季、秋季、冬季呈不显著增大趋势,在夏季呈不显著减小趋势,春、夏、秋、冬四季多年平均积雪覆盖率分别为0.16、0.06、0.13、0.17。②澜沧江源区西南和北部沿界狭长区域积雪覆盖率在四季均呈增大趋势,东南区域积雪覆盖率呈减小趋势;其中,西北部区域积雪覆盖率增幅在冬季达到最大,可达3%/a。③SRM在澜沧江上游具有较好的适用性,1—5月份率定期和验证期确定性系数分别为0.87和0.78。研究结果对高寒区融雪径流模拟研究具有一定的参考价值。

以长江源区为研究区域,采用沱沱河站、直门达站实测径流,利用北大西洋涛动指数(NAOI)分析北大西洋涛动(NAO)的强度,研究NAO对两站冬季、夏季及全年径流丰枯变化的影响,采用相关分析和交叉小波变换分析NAO与两站径流的多尺度相关特性,从海-气耦合影响大气环流角度分析NAO对长江源区径流的可能影响机制。研究结果表明,长江源区冬季径流受NAO影响较大,2000年之前NAO强年对应径流偏枯概率较大,NAO弱年对应径流偏丰概率略大;夏季径流受长江源区气温影响更为显著,对于NAO强弱的响应不如冬季明显。NAOI与长江源区沱沱河站、直门达站径流在年代际变化规律上具有很好的趋同性,而对于年际或更短时间尺度上的相关关系不甚密切。沱沱河站、直门达站月径流与NAOI两者之间在整个1960—2020年时间轴上具有8~16个月时间尺度上的共振周期。两站与NAOI分别在1970年代、1980年代之前呈现同频同位相变化态势;之后呈现反位相变化态势。分析其作用机制可知,NAO作为北大西洋地区最重要的气候模态,通过大气遥相关和Rossby波列直接影响季风和西风带的强弱,进而调整青藏高原上空水汽输送和辐合、辐散场的分布,从而影响长江源区降水和径流的时空分布。

青藏高原是气候变化的敏感区，其积雪在区域水文循环和气候系统中具有重要作用。本文利用1980—2020年逐日无云积雪覆盖遥感数据，分析了该地区近40年的积雪面积、积雪覆盖日数的分布特征和变化趋势。结果表明：青藏高原地区积雪分布具有明显的空间分异和垂直地带性分布特征，阿姆河流域、印度河流域、塔里木盆地、恒河流域、怒江流域和雅鲁藏布江流域的高海拔山区是积雪广泛分布的地区。在水文年内，高原地区积雪覆盖率呈单峰变化，8月上旬积雪面积最小，1月中下旬达到最大，分别占高原总面积的5.2%和38.6%；40年间，高原地区平均积雪面积以3.9×10⁴ km²·（10a）^-1的趋势显著减少（P<0.05）；积雪覆盖日数以0.47 d·a^-1的趋势显著减少，高原71.4%的区域积雪覆盖日数呈减少趋势，呈显著减少的区域约占55.3%；17.1%的区域积雪覆盖日数呈显著增加趋势，且主要分布在5 200 m以上的高海拔山区，在海拔5 200~5 900 m之间的区域，积雪覆盖日数的增加率随海拔升高而增加。

The Tibetan Plateau （TP） is sensitive to climate change， where snow plays a vital role in the regional hydrological cycle and climate system. This paper uses the daily cloud-free snow cover remote sensing data from 1980 to 2020 to analyze the distribution characteristics and variation trends of the snow cover area （SCA） and snow cover days （SCD） for a hydrological year from August 1 to July 31 in the next year over the TP. The results show that： （1） The snow in the TP shows an apparent spatial differentiation and a vertical zonal distribution characteristic. It is widely distributed in the high-altitude mountainous areas in the Amu Darya， the Indus， the Tarim， the Ganges， the Salween， and the Brahmaputra basins. （2） During the hydrological year， the snow cover extent shows a unimodal variation in the plateau with the minimum in early August and the maximum in mid-late January， accounting for 5.2% and 38.6%， respectively. （3） In the past 40 years， the average SCA shows a significantly decreased trend with 3.9×10⁴ km²·（10a）^-1 （ P<0.05）. （4） The SCD in the study area mainly shows a significant decrease with 0.47 d·a^-1. Up to 71.4% of the plateau shows a decreasing trend， and 55.3% of the area is significantly decreased （ P<0.05）. And in 17.1% of the region， the SCD shows a significant increasing trend， and it is mainly distributed in the high-altitude mountainous areas above 5 200 m. Moreover， in the areas from 5 200 m to 5 900 m， the increase in SCD increased with altitude.

In recent decades, the existence of a relationship between snow cover on the Tibetan Plateau (TP) and East Asian summer monsoon (EASM) rainfall has been emphasized. According to recently published studies this snow-monsoon relationship experienced a shift after 1990. Although the changing snow-monsoon relationship has been studied, the causes of the interdecadal changes remain unclear. This study assesses the associations of TP spring snow cover with EASM rainfall before and after 1990 and explores what possible mechanisms could be responsible for the interdecadal changes. Correlation and composite analyses were used to assess the strength of the relationship between TP spring snow cover and EASM rainfall and to analyze the atmospheric and land surface patterns associated with high snow cover. The outcomes suggest that the relationship between TP spring snow cover and EASM rainfall changes from partially negative to positive over all regions of the TP from 1968–1990 (P1) to 1991–2019 (P2), implying that more snow cover is associated with less (more) EASM rainfall during P1 (P2). In P1, years with high snow cover are associated with an anomalous cyclone southwest of the TP (positioned over Iran and Pakistan) in spring, which persists into the following summer, partly due to the underlying snow cover. The anomalous cyclone is accompanied by downstream anomalies over East Asia, which form a strong east-west oriented wave pattern and induce a northerly inflow of dry air over East Asia, reducing rainfall over the northern EASM domain. In P2, high snow cover years are associated with an anomalous cyclone over the western TP, which weakens and loses its significance in May-June and summer, partly due to a decline in snow forcing. Southeastward propagation of wave energy in May-June initiates the formation of an anomalous anticyclone over southeastern China and the western North Pacific. Concurrently, a meridional circulation develops over East Asia that enhances the southwesterly moisture inflow, resulting in increased EASM rainfall. The changing snow-monsoon relationship can be linked to different wave train patterns resulting from changes in the background zonal wind and meridional temperature gradients. This research contributes to a better understanding of the changing snow-monsoon relationship.

长江源区位于青藏高原腹地,海拔高、气温低,自然条件恶劣,水文气象监测站点很少,基础资料缺乏,水循环研究相对较少。综述了长江源区水循环研究和观测现状及其存在的问题和困难。目前,长江源区监测站点少且布设不合理,仪器设备运行维护困难,监测数据不能满足相关要求;对水资源变化趋势、下垫面径流效应、水循环机制、地下水运移等水循环机理方面的研究不够深入;水文模拟模型结构有待完善、适用性和通用性还有待验证。提出应采取多部门多学科联合,完善观测站点和平台建设,加强科学研究与国际合作、信息服务和社会效益等措施,促进原位观测和基础理论研究,在观测手段和三水转换、水量平衡、水热耦合等水循环机理,以及高寒水文模型研发和全球气候变化影响等方面加强研究和创新。

Located in the hinterland of Qinghai-Tibet Plateau, the source region of the Yangtze River is featured with high altitude, low temperature, and harsh natural conditions. As a result, with the lack of hydrometeorological monitoring and basic data, study on the hydrological cycle in this region is inadequate. In this paper, the status of researches and observations of hydrologic cycle in the source region of Yangtze River is reviewed, and existing problems and challenges are expounded. First of all, the monitoring data could not meet research requirements due to insufficient monitoring stations and their unreasonable locations as well as difficulties in operating and maintaining equipment in such unfavorable circumstances. Research on the mechanism of hydrologic cycle needs to be deepened. Such mechanism involves the trend of water resources variation, runoff of underlying surface, groundwater transport, and etc. Moreover, the structure of hydrological simulation models should be enhanced, and the applicability and versatility await verification. Measures to tackle these problems are presented as follows: monitoring stations and platforms need to be upgraded by collaborative efforts from multi-departments and trans-disciplines; international corporation in scientific research can be intensified; information service and social benefits should be taken into consideration; prototype observation and fundamental theoretical research need to be improved. Innovations should also boost in terms of observation approach, atmospheric-solid-liquid water conversion, water balance, hydro-thermal coupling, hydrologic models for alpine area, as well as global climate change impact.

. The Tibetan Plateau (TP) region, often referred to as the Third\nPole, is the world's highest plateau and exerts a considerable influence on\nregional and global climate. The state of the snowpack over the TP is a\nmajor research focus due to its great impact on the headwaters of a dozen\nmajor Asian rivers. While many studies have attempted to validate\natmospheric reanalyses over the TP area in terms of temperature or\nprecipitation, there have been – remarkably – no studies aimed at\nsystematically comparing the snow depth or snow cover in global reanalyses\nwith satellite and in situ data. Yet, snow in reanalyses provides critical\nsurface information for forecast systems from the medium to sub-seasonal\ntimescales. Here, snow depth and snow cover from four recent global reanalysis products, namely the European Centre for\nMedium-Range Weather Forecasts (ECMWF) ERA5 and ERA-Interim reanalyses, the\nJapanese 55-year Reanalysis (JRA-55) and the NASA Modern-Era Retrospective analysis\nfor Research and Applications (MERRA-2), are\ninter-compared over the TP region. The reanalyses are evaluated\nagainst a set of 33 in situ station observations, as well as against the\nInteractive Multisensor Snow and Ice Mapping System (IMS) snow cover and\na satellite microwave snow depth dataset. The high temporal correlation\ncoefficient (0.78) between the IMS snow cover and the in situ observations\nprovides confidence in the station data despite the relative paucity of\nin situ measurement sites and the harsh operating conditions. While several reanalyses show a systematic overestimation of the snow\ndepth or snow cover, the reanalyses that assimilate local in situ\nobservations or IMS snow cover are better capable of representing the\nshallow, transient snowpack over the TP region. The latter point is clearly\ndemonstrated by examining the family of reanalyses from the ECMWF, of which\nonly the older ERA-Interim assimilated IMS snow cover at high altitudes,\nwhile ERA5 did not consider IMS snow cover for high altitudes. We further\ntested the sensitivity of the ERA5-Land model in offline experiments,\nassessing the impact of blown snow sublimation, snow cover to snow depth\nconversion and, more importantly, excessive snowfall. These results suggest\nthat excessive snowfall might be the primary factor for the large\noverestimation of snow depth and cover in ERA5 reanalysis. Pending a\nsolution for this common model precipitation bias over the Himalayas and the TP,\nfuture snow reanalyses that optimally combine the use of satellite snow\ncover and in situ snow depth observations in the assimilation and analysis\ncycles have the potential to improve medium-range to sub-seasonal forecasts\nfor water resources applications.

三江源地区气象站点稀疏，依靠地面台站数据难以反映地面真实积雪情况。利用卫星遥感数据引入重心模型分析了三江源地区1980—2019年4个积雪参数（积雪日数、积雪深度、积雪初日和积雪终日）的时空动态特征，利用Mann-Kendall检验和Sen斜率估计分析了积雪和气候因子的变化趋势，并探究积雪对气候变化的响应。结果表明：1980—2019年三江源地区呈现积雪日数和积雪深度减少、积雪初日推迟、积雪终日提前的变化趋势，而该区域同期的气温和降水量则呈现上升趋势；4个积雪参数重心均呈现出东移趋势，而同期气温重心则呈现西移趋势，气温重心位置西移速率分别是积雪日数和积雪深度重心位置东移速率的6倍和2倍。这表明该区域4个积雪参数以及气候因子的变化趋势具有较强的空间异质性，西部气温升高速率大于东部，导致西部积雪日数和积雪深度减少速率同样大于东部，从而导致气温重心西移而积雪参数重心东移。澜沧江源区积雪日数减少、积雪深度减少、积雪初日推迟以及积雪终日提前的速率最大，其次是长江源区和黄河源区。进一步的相关性分析表明，三江源地区年平均气温的升高是导致积雪日数和积雪深度减少、积雪初日推迟、积雪终日提前的主要影响因子，积雪日数对气温升高响应最敏感，其次是积雪深度、初日和终日；而年降水量与4个积雪参数的相关性均不显著。研究可为三江源地区水资源和生态环境保护提供基础资料和理论依据。

Meteorological stations in the Three-River-Source region is sparse， and only analyzing ground station data fails to reflect true snow cover on ground. In this study， based on remote sensing data， we applied gravity center model to analyze spatiotemporal dynamic characteristics of four snow cover parameters including snow cover days， snow depth， snow cover onset date and snow cover end date from 1980 to 2019. Mann-Kendall test and Sen’s slope estimation were used to analyze trends of the four snow cover parameters and climate factors. We finally explored its response to variations in annual mean air temperature and annual precipitation in the Three-River-Source region. The results indicated that snow cover days and snow depth showed downward trends， and snow cover onset date delayed and snow cover end date advanced from 1980 to 2019 in the Three-River-Source region， while air temperature and precipitation showed upward trends. Gravity center of the four snow cover parameters showed eastward trends， while gravity center of air temperature showed a westward trend. The westward speed of gravity center of air temperature was 6 times and 2 times the eastward speed of snow cover days and snow depth， respectively. These indicated that trends of the four snow cover parameters and climate factors in this region showed strong spatial heterogeneity. The increase rate of air temperature in the west was greater than that in the east， which leads to a greater decrease rate of snow cover days and snow depth in the west than in the east. It was responsible for the westward of gravity center of air temperature， and the eastward of gravity center of snow cover parameters. The Lancang River Source region had the highest rate of decrease in snow cover days and snow depth， delay of snow cover onset date and advance of snow cover end date， followed by the Yangtze River Source region and the Yellow River Source region. Further correlation analysis indicated that the increase in air temperature was primarily responsible for the decrease in snow cover days and snow depth， delay of snow cover onset date and advance of snow cover end date. Snow cover days was most sensitive to air temperature rise， followed by snow depth， snow cover onset date and end date. The correlation between annual precipitation and the four snow cover parameters was not significant. This research can provide basic data and theoretical basis for the protection of water resources and ecological environment in the Three-River-Source region.

本文根据2300余个地面气象台站从1951年（或建站）到1980年逐日积雪与降雪观测资料,计算出我国年平均降雪补给量为3451。8 X 108m3,冬季平均积雪贮量为535。6 X 108m3,阐明了季节雪资源的地理分布规律,季节分配特征和长期变化趋势。指出了CO2增温可能导致我国季节雪资源分布的区域分异倾向进一步加骤,引起北方土壤干旱化。三十年来,雪资源的波动是全球海气异常的结果。多雪冬天与厄尔尼诺南方涛动相同步。雪资源的两个正、负距平时期与我国农田受旱面积的两个明显的低高值时期基本吻合。长期变化趋势准确地反映出了全球气温变化过程,并与气温变化成正相关。

Based on data on daily depth and density of snowcover and snowfall recorded at more than 2300 weather stations of China from 1951 up to 1980, the snow resources have been evaluated and their secular variations have been clarified.

三江源区地处青藏高原腹地， 是中国长江、 黄河和澜沧江三大河流的发源地，并且作为全球气候变化的“敏感区”， 气候变化无疑会对该区域的气候、 环境和水资源产生深刻影响。本文综述了三江源区近50~60年气候、 环境和水资源变化的事实， 主要认知如下： （1）三江源区总体呈现升温趋势， 升温速率约为0.33 ℃·（10a）^-1， 是青藏高原同期的1.2倍。（2）三江源区降水总体呈现增加趋势， 趋势约为6.653 mm·（10a）^-1， 为青藏高原同期降水增加率的71%。（3）三江源区年最低和最高气温呈现显著增加趋势， 且冷季增幅大于暖季。降水量的变化趋于稳定， 降水变率减小， 严重干旱或暴雨事件均呈减少趋势。（4）三江源区南部积雪日数最多且呈显著增加趋势， 黄河源区整体上呈现积雪初日推迟、 终日提前、 积雪期缩短和积雪日数减少趋势。（5）在升温影响下， 冻土严重退化， 并引起沼泽湿地的发育， 在降水增加和气温升高引起的融水增加的双重影响下， 三江源区湖泊沼泽持续扩张。（6）尽管三江源区降水总体呈增加趋势， 但径流变化存在较大的区域差异， 长江源区径流显著增加， 而黄河源区则为减少趋势， 直门达和香达水文站径流变化倾向率分别为6.69×10⁸ m³·（10a）^-1和1.1×10⁸ m³·（10a）^-1。最后， 对气候变化影响下水循环变化及其对环境和水资源影响的研究现状进行了讨论， 并呼吁加强大气水文过程的耦合研究， 量化气候变化、 人类活动及陆气耦合多圈层相互作用的研究以加强其影响区域气候环境和水循环的认识， 为三江源区适应气候变化和青藏高原生态文明建设提供参考。

The Three-river sources regions （TRSR）， located on the Qinghai-Xiang Plateau （QXP）， are the source regions of Yangtze， Yellow and Lancang River.Under the background of global climate change， the QXP was considered as the “sensitive region” and the “promoter region” of climate change， which will definitely affect the regional climate， environment， and water resources on the TRSR.This paper reviews the facts of variations of climate， environment and water resources in the recent 5~6 decades.The main conclusions are as follows： （1） Air temperature increased on the TRSR with a trend of 0.33 ℃·（10a）^-1， which is 1.2 times of the rate on QXP.（2） Precipitation increased on the TRSR with a trend of 6.653 mm·（10a）^-1， but the trend was 71% of the QXP.（3） The minimum and maximum air temperature increased significantly， with the trend in the cold seasons higher than the warm seasons.（4） Snow days on the south of the TRSR increased， but decreased on the source region of the Yellow river.（5） Under the climate warming， the permafrost degraded， in combing with the precipitation enhancement， the lakes and the wetlands were developed.（6） Although precipitation on the TRSR enhanced， runoff shows different trends， with it increased on the sources of Yangtze river （the trend of runoff in Zhimenda station is 6.69×10⁸ m³·（10a）^-1）， and decreased on the Yellow river （the trend of runoff in Xiangda station is 1.1×10⁸ m³·（10a）^-1）.At last， the water cycle changes under the warming and its influences on water resources were discussed， according to which it is important to do more investigations on the multi-sphere interactions to distinct the contribution to water resources from climate change and human activities.These kinds of knowledge will benefit for the TRSR to adapt climate change and supply references for the TRSR park construction.

通过高原积雪和欧亚积雪与我国夏季降水的相关分析和统计检验,表明冬春季雪盖对我国夏季旱涝有重要的影响,虽然冬季和春季雪盖与我国夏季降水的相关分布存在差异,总趋势大致相仿。但是,冬春季高原积雪和欧亚积雪与我国夏季降水的相关分布基本是相反的,其中高原积雪与长江中下游和西北东部地区夏季降水为正相关,欧亚积雪与东北和华北东部以及西南地区降水为正相关。冬季高原积雪异常偏多时,长江流域夏季易发生洪涝,这也是汛期降水预测中的一个重要信号。

The relationships between the snow cover in Eurasia and the Qinghai-Xizang plateau(QXP) in pre-winter and the summer rainfall in China were studied and tested.The result shows that there is the impotant effect of the snow cover on the summer rainfall in China.The relationship in winter and spring snow cover with the summer rainfall are about the same.But the relationship distributions between the snow cover in Eurasia and QXP and the summer rainfall in China are nearly contrary.The main positive correlation for snow cover in QXP occurs in the mid-lower reaches of the Yangtze River and North-East China and the east region of North China and South-West China.The flood of the Yangtze River valley in summer usually is occured when anomalous snow cover in QXP would be above normal in winter.This is the important indicator for the prediction of rainfall in summer.

长江源区对气候变化的响应较为敏感,其河川径流也随之产生了明显的变化。根据长江源区直门达水文站及长江源区5个气象站1960—2022年实测水文气象资料,分析长江源区年径流和季节性径流变化规律。利用相关分析、交叉小波变换及主成分分析法,分析径流变化与主要气象要素之间的关联性。研究结果表明,近63 a来直门达站年径流呈现显著上升的趋势,尤其是近20 a径流大幅度增加。1960—2000年期间,长江源区各季节性径流变化趋势较为平稳。2000—2022年期间,各季节性径流均呈现出增加的态势并延续至今。对直门达站径流影响最为密切的气象要素主要为降水、气温、相对湿度等。

The source regions of the Yangtze River (SRYZ) and the Yellow River (SRYR) are sensitive areas of global climate change. Hence, determining the variation characteristics of the runoff and the main influencing factors in this region would be of great significance. In this study, different methods were used to quantify the contributions of climate change and other environmental factors to the runoff variation in the two regions, and the similarities and differences in the driving mechanisms of runoff change in the two regions were explored further. First, the change characteristics of precipitation, potential evapotranspiration, and runoff were analyzed through the observational data of the basin. Then, considering the non-linearity and non-stationarity of the runoff series, a heuristic segmentation algorithm method was used to divide the entire study period into natural and impacted periods. Finally, the effects of climate change and other environmental factors on runoff variation in two regions were evaluated comprehensively using three methods, including the improved double mass curve (IDMC), the slope change ratio of cumulative quantity (SCRCQ), and the Budyko-based elasticity (BBE). Results indicated that the annual precipitation and potential evapotranspiration increased during the study period in the two regions. However, the runoff increased in the SRYZ and decreased in the SRYR. The intra-annual distribution of the runoff in the SRYZ was unimodal during the natural period and bimodal in the SRYR. The mutation test indicated that the change points of annual runoff series in the SRYZ and SRYR occurred in 2004 and 1989, respectively. The attribution analysis methods yielded similar results that climate change had the greatest effect on the runoff variation in the SRYZ, with a contribution of 59.6%~104.6%, and precipitation contributed 65.3%~109.6% of the increase in runoff. In contrast, the runoff variation in the SRYR was mainly controlled by other environmental factors such as permafrost degradation, land desertification, and human water consumption, which contributed 83.7%~96.5% of the decrease in the runoff. The results are meaningful for improving the efficiency of water resources utilization in the SRYZ and SRYR.

针对青藏高原高海拔山区积雪覆盖变化不明和积雪覆盖日数研究不足等问题，利用NOAA IMS雪冰产品，对青藏高原2004—2021年积雪覆盖日数进行了分析。结果表明：近17 a间青藏高原积雪覆盖日数出现了显著增加趋势，增幅达11.5 d·（10a）^-1，其中，高原中东部和北部高寒地区以增加趋势为主，南部和西北部高山区以减少趋势为主；青藏高原积雪覆盖日数呈现非常显著的海拔依赖性，海拔越高，积雪持续时间越长，覆盖日数越多，海拔2000 m以下，平均覆盖日数不足5 d，而海拔6000 m平均超过157 d；青藏高原年平均积雪覆盖日数是71.1 d，其中冬季平均最多，为27.2 d，其次是春季（22.1 d）和秋季（14.5 d），夏季平均最少，仅5.3 d。在青藏高原总体气候暖湿化背景下，高山高纬度地区降水增加引起的积雪覆盖增加有效弥补了因气温升高引起的高原积雪覆盖减少的趋势。

The Qinghai-Tibet Plateau is renowned as the water tower of Asia and the third pole of the world. Changes in the water resources of the Qinghai-Tibet Plateau has a profound impact on the water resources security and people’s lives in China and its neighboring countries. The temporal and spatial changes of surface and groundwater resources in the Qinghai-Tibet Plateau from 1997 to 2018 are studied using linear tendency estimation, Mann-Kendall trend test and Pearson correlation coefficient method based on the data of <i>Qinghai Water Resources Bulletin</i> and <i>Tibet Water Resources Bulletin.</i> The results of the study indicate that: (1) water resources in the Qinghai-Tibet Plateau is extremely concentrated, mainly in Shannan, Nyingchi City, the Yarlung Zangbo River Basin and the river basins of southern Tibet. The south and east of Qinghai-Tibet Plateau boasts abundant water resources while the north and the west less. (2) From 1997 to 2018, the amount of surface water resources on the Qinghai-Tibet Plateau showed an insignificant upward trend, while the amount of groundwater resources (-16.64 billion m³/(10 a)) a significant downward trend. The change trends of water resources differed notably in spatial scale, with the surface water resources (9.83 billion m³/(10 a)) and groundwater resources (5.8 billion m³/(10 a)) in most areas of Qinghai Province in north Qinghai-Tibet Plateau displaying a significant upward trend, and surface water resources in most parts of the southern Tibet Autonomous Region an insignificant downward trend, groundwater resources a significant downward trend (-19.54 billion m³/(10 a)). (3) In recent years, the temperature in Qinghai-Tibet Plateau has had a very significant increasing trend, with the rising rate reaching 0.49 ℃/(10 a). The precipitation of Qinghai Province in the northern part of the Qinghai-Tibet Plateau showed a significant increase trend, while the southern part an insignificant downward trend. In conclusion, precipitation is the major factor that induces the changes of surface water resources and groundwater resources in the Qinghai-Tibet Plateau.

基于长江源区1956—2016年8个测站的逐日降水数据,采用集中度、集中期、Mann-Kendall趋势检验和滑动T检验法等统计方法,分析了长江源区近60 a来降水量序列的空间分布特征、年际和年内变化趋势、突变和周期变化特征等。结果表明:① 长江源区降水量呈现明显的增加趋势并通过显著性检验,增加速率10.2 mm/(10 a),多年平均降水量为344.8 mm;②长江源区的降水量在时间维度上存在显著的不均匀现象,多数聚集于为6—9月份,约占全年降水量的81.1%;③长江源区的降水量序列在1997年发生显著性突变,降水量变化存在25 a左右的第一主周期,第二、第三周期分别为3 a和10 a;④长江源区内各站点年降水量增加趋势空间变异性较大,总体呈现通天河上游降水量增加速率大于下游。研究结果可为长江流域水资源可持续利用和生态安全提供重要的科学依据。

Based on the daily statistical data of eight stations in the source area of the Yangtze River from 1956 to 2016, we examined the spatial distribution, intra-annual and inter-annual trends, abrupt change and periods of precipitation in the headwaters of the Yangtze River in the last six decades by using precipitation concentration degree, precipitation concentration period, Mann-Kendall trend test and moving-T test. Results revealed that: 1) the precipitation in the headwaters of the Yangtze River presented an evident increasing trend, passing the significance test with the growth rate amounting to 10.2 mm/10 a and the multi-year average precipitation reaching 344.8 mm. 2) Precipitation in the headwaters of the Yangtze River was significantly uneven in time dimension, most concentrated between June and September, accounting for 81.1% of the whole year. 3) Precipitation changed abruptly in 1997, with the first principal period of 25 years, the second and the third principal period of 3 years and 10 years, respectively. 4) The annual precipitation growth varied largely in spatial scale among different stations, i.e., the growth rate of precipitation in the upstream of Tongtian River was larger than that in the downstream. The research findings offer support for sustainable water resources utilization and ecological security in the Yangtze River basin.

青藏高原被称为“亚洲水塔”和“第三极”,青藏高原水资源变化对我国乃至周边众多国家的水资源安全及人民生活均产生深远的影响。利用青藏高原周边103个气象站点及国内外8种卫星遥感与再分析数据,采用线性倾向估计、Mann-Kendall趋势检验法和相关系数法对1980—2019年青藏高原降水量变化趋势及各数据集适用性进行了研究,利用相关系数(R)、相对误差(BIAS)及均方根误差(RMSE)对这8种卫星遥感与再分析数据适用性进行了评估分析。研究结果表明:①8种降水数据集均能够反映青藏高原降水的空间格局,但精度存在明显差异,其中阳坤的CFMD数据集质量最高,相对误差为13.64%。②多种气象数据均表明近40 a青藏高原整体降水量显著上升的面积为12.8%~69.82%,各降水数据集均在地形较为复杂或降水量较低的干旱地区有着更高的相对误差,此外稀疏的实测站点也对数据集质量影响较大。③近40 a青藏高原66%地区降水量呈上升趋势,中部与北部地区上升趋势显著,而青藏高原东南部雅鲁藏布江、怒江、澜沧江及长江源区下游的降水量则呈显著的下降趋势。④青藏高原各流域降水中黄河源区降水量上升最为快速,上升速率在5 mm/a左右,怒江流域、雅鲁藏布江流域下游地区降水量下降速度最快,达到9 mm/a以上。