气候变化背景下中国陆地水循环时空演变

水循环是气候系统各子系统相互作用过程中一个最活跃的枢纽,受气候变化影响显著。本文采用观测和多套再分析数据,系统分析了1979年以来中国及各大流域大气水汽含量、降水、蒸散发和地表径流等水循环要素年际变化。研究发现,1979-2018年,中国陆地整层大气水汽含量和水汽收支呈显著上升趋势;水汽收支除在松花江和西南诸河略有下降,其余流域均呈上升趋势;降水除西北诸河流域呈现显著上升趋势外,其余流域变化不显著;蒸散发整体呈微弱增加,但南方大部流域呈现显著的减小趋势;除西北诸河径流显著上升趋势外,北方大部分流域地表径流呈现减少趋势,而南方流域的径流变化趋势复杂多样。相对1979-2000年,21世纪以来中国年平均气温上升约0.63℃,年降水量、大气水汽含量分别增加0.5%和1.2%,水汽总输入和输出量均减小,降水再循环率增加10.9%。进入21世纪,中国陆地水资源一级分区内循环均较前20 a活跃,降水再循环率除松花江和辽河流域外,均有所增加。其中,海河、黄河、淮河和西北诸河流域的水汽和蒸发形成的降水都有所增加;辽河流域蒸发形成的降水有所增加,但输入水汽减少导致流域降水减少最多;松花江、长江、珠江和西南诸河流域蒸发形成的降水增加,输入水汽减少导致降水略有减少;东南诸河蒸发形成的降水略有增加,但整体变化不大。     

黄河流域蒸散发与气温和降水以及风速的相关性分析

黄河流经我国干旱半干旱地区,其流域蒸散发变化对当地的生态安全和经济发展尤其重要。本文利用欧洲中期天气预报中心第五代再分析产品（ERA5）定量分析了1979-2020年黄河流域蒸散发的时空变化特征,并结合气温、降水和风速数据,对黄河流域蒸散发与3种气候因子进行了相关性分析。结果表明：黄河流域蒸散发在1979-2020年呈波动下降趋势,空间分布差异明显,源区附近蒸散发上升,上游的干旱区附近蒸散发基本不变,而中游和下游地区主要呈现下降趋势。1979-2020年黄河流域气温持续上升,降水呈波动下降趋势,风速呈上升趋势。对黄河流域蒸散发与气候因子的相关性分析表明,蒸散发与气候因子的相关性空间差异较为明显,蒸散发与气温、风速呈负相关,与降水呈正相关的区域占流域的较大部分;而在复相关性方面,黄河流域大部分地区蒸散发与气候因子的相关性较强,其中以流域上游的干旱区附近复相关性最强。研究黄河流域不同地区蒸散发与气候因子的相关性可为黄河流域水资源的开发管理和区域气候调节提供科学参考。     

基于SWAT模型的洪湖流域供水资源模拟研究

利用SWAT分布式水文模型,对洪湖流域1961—2011年供水资源变化情况进行模拟。结果表明:SWAT模型对洪湖流域供水资源模拟适用性良好。近51 a流域年平均地表径流和降水量增加趋势相当,且降水量峰值对应地表径流和地下径流均较高。流域在1960s、1970s相对偏枯,1980s后降水相对丰沛,流域呈现由干转湿的变化。进入21世纪后,流域又趋于偏枯。流域季节降水量、地表径流、地下径流、蒸散发量及土壤含水量变化最大值均出现在夏季,最小值均出现在冬季,但丰、枯年季节分配不同,各要素月季节分布差异较大。洪湖年均入湖水量呈略增加趋势,春、夏季增加趋势较为明显。     

基于SPEI的中国干湿变化趋势归因分析

选用1960—2012年中国气象站点资料,利用标准化降水蒸散指数SPEI(Standardized Precipitation Evapotranspiration Index),研究了中国干湿变化趋势及其原因。过去52 a,中国干湿变化由西北向东南呈现"+-+"的空间分布状况,其中黄河流域、长江流域西部、西南流域东南及珠江流域西部显著变干;淮河流域中西部和西北流域大部显著变湿;通过数值试验,定量计算了参考蒸散发及降水对干湿趋势的贡献状况。就中国总体而言,年平均参考蒸散发显著减少抵消了由年降水量减少导致的干化趋势,呈微弱变湿趋势;其次,降水仍然是多数区域干湿变化的主导因素(黄河流域中部、长江流域、西南流域、珠江流域及东南流域);同时,参考蒸散的影响值得引起注意,其在辽河流域、海河流域、淮河流域及西北流域对干湿趋势的贡献均超过降水贡献。     

基于CMADS驱动SWAT模型的富春江水库控制流域水量平衡模拟

以富春江水库控制流域为研究区域,利用中国大气同化驱动数据集（CMADS V1.1）驱动SWAT水文模型,对富春江水库控制流域进行了逐日径流模拟,探讨了流域2008-2016年径流变化及水量平衡过程。结果表明：CMADS V1.1数据集驱动SWAT模型对研究区域的径流变化具有较好的模拟效果,在验证期,逐日模拟的效率系数大于0.70,决定系数大于0.75,达到了模型评价标准。在流域水量平衡各项中,地表径流和蒸散发为主要的输出项,分别占降水量的57.2%和36.2%,其中蒸散发量年际变化较为平稳。降水量、地表径流量、土壤对地下水补给、地下侧流量、蒸散发量最大值均出现在6月,最小值均出现在1月。流域径流量以地表径流为主,其在各个月份与月降水变化趋势基本一致。而基流量较小,且各月基流量对降水量的响应并不显著。     

1961—2008年淮河流域气温和降水变化趋势

利用淮河流域170个地面气象观测站观测数据,统计分析了淮河流域1961—2008年间气温和降水的时空变化趋势。结果表明:48 a间淮河流域年平均气温呈显著上升趋势,冬季平均气温的增温幅度最大,春、秋次之;年极端最低气温亦呈显著上升趋势,年极端低温日数(满足该站极端低温阈值)则呈明显下降趋势;流域西北部年极端最高气温呈显著下降趋势,流域西部年极端高温日数(满足该站极端高温阈值)呈显著下降趋势;降水量总体变化趋势未通过统计检验,但1990s开始,秋季降水量呈下降趋势,2000年之后年降水量明显增加,夏季降水量亦增加;春季和秋季降水日数呈显著下降趋势,夏季和冬季无明显变化。     

气候变化对水文循环的影响

水文循环是地球上海洋、陆地和大气之间相互作用中最活跃且最重要的枢纽,受气候变化影响最为显著。本文回顾了气候变化对全球水文循环的影响,并对20世纪60年代以来中国降水、蒸散发、地表径流及大气水汽含量等陆地水文循环要素变化进行了评估。气候变暖使得全球水文循环加强,观测数据表明自1970年以来,全球对流层和地表水汽含量呈现增加趋势,但由于监测网络在空间覆盖和时间响应的限制,热带水汽增加与环流减弱之间相互影响,使得气候变化对区域水文循环的影响不确定性较大。在全球气候变化背景下,中国水文循环符合全球水循环变化的特征,又表现出更为复杂的区域特征,各个流域间空间差异增大。大气水汽含量在80年代后呈现上升的趋势;60年代以来,中国降水平均态虽然无明显变化但空间差异显著增加,实际蒸散发平均值微弱增加,空间差异增大,地表径流空间差异增大,某些流域呈现减少趋势。21世纪以来,由蒸散发再凝结形成的降水量增加,大气内循环活跃程度加大。     

珠江流域实际蒸散发的时空变化及影响要素分析

采用基于互补相关理论的平流-干旱模型,根据60个气象站1961—2010年气象资料,计算并分析了珠江流域实际蒸散发（ETa）的时空变化特征,通过对实际蒸散发的辐射能量项、空气动力学项与主要气象要素的相关分析,对珠江流域实际蒸散发的时空变化进行了归因研究。结果表明:（1） 珠江流域多年平均实际蒸散发量为665.6 mm/a。1961—2010年,珠江流域实际蒸散发量呈明显的下降趋势,下降幅度为-24.3 mm/(10 a)。夏秋季节实际蒸散发的下降对年际尺度实际蒸散发的下降具有明显的贡献。（2） 珠江流域东南沿海地区年实际蒸散发量较高（大于690 mm）,该区年实际蒸散发量呈现显著的下降趋势。流域中部有一条呈东北-西南走向的条带状实际蒸散发低值区,年均实际蒸散发量在630 mm以下,但该区域的时间变化趋势不明显。（3） 气温日较差和日照时数的下降以及大气压的增加使得辐射能量项的下降,是造成实际蒸散发下降的主要原因;平均气温、最高、最低气温的上升使空气动力学项呈现增加趋势,从而在一定程度上贡献于实际蒸散发的下降。春秋冬三季平均风速的下降引起空气动力学项的下降趋势或减缓其增加趋势,反过来在一定程度上减缓了实际蒸散发的下降趋势。      

大渡河流域积雪特征及其与气候要素和径流的关系

利用MOD10A2遥感影像提取大渡河流域2010~2014年积雪覆盖数据,结合水文气象站点数据分析了大渡河流域积雪时空分布特征及气象因子-积雪面积-径流之间的关系。结果表明:年平均积雪面积最大的是康定,最小的是泸定。积雪在冬季最大,夏季积雪最少。积雪面积变化随月份起伏明显,积雪过程集中在10月到次年4月。降水和气温变化较一致,其峰值滞后于积雪面积峰值。积雪和气温、降水的相关性表明,积雪面积与气温、降水呈负相关,且气温与积雪面积相关性更大。径流的变化具有周期性,5月开始迅速增大,7月达到最大值。径流和积雪以及气象因子的相关性分析表明,径流与积雪面积呈负相关,与气温和降水都是正相关,且径流与降水相关性更大。      

安康水库蓄水前后上游气候变化特征

利用陕西省安康水库上游气象站点的月及日降水、气温、蒸发等气候资料,分析了安康水库蓄水前后上游流域气候变化特征。分析结果表明,年降水量呈逐年代减少趋势,年平均温度呈增暖趋势,年蒸散量呈减少趋势;蓄水后年及主汛期降水量、雨日、暴雨日数、极端强降水概率、蒸散量均比蓄水前减少,平均气温比蓄水前升高,其中冬季升温幅度最大;主汛期和年降水量、平均气温蓄水前后差异显著,冬季蒸散量蓄水前后差异显著。近45年来汉江径流量呈下降趋势,降水对径流影响显著。     

哈萨克斯坦北部伊希姆河径流对气候变化和人类活动的响应

基于1933—2016年哈萨克斯坦北部伊希姆河彼得罗巴甫洛斯克水文站流量观测数据以及流域内格点气象数据,利用线性趋势法、Mann-Kendall检验、相关普查法和累积量斜率变化率比较法等方法,探讨了气候变化背景下伊希姆河流量变化及其主要驱动因子。结果显示：(1)伊希姆河流域近84年气温和降水呈上升趋势,且在20世纪70年代后增加趋势更加明显。(2)伊希姆河流量年内分布不均,年际流量变化总体呈下降趋势,但趋势不明显。(3)伊希姆河流量受流域内降水和气温共同影响,其中降水与流量相关性最大,且降水的变化对流量补给具有滞后性,6—9月气温对同时期流量影响较大。(4)T₁时段(1969—1996年)和T₂时段(1997—2016年)与T时段(1933—1968年)相比,气候变化对流量减少的贡献率分别为16.09%和44.83%,而人类活动对流量减少的贡献率为83.91%和55.17%。流域内水资源的开发及利用、人口数量和土地利用方式的变化等人类活动因素在很大程度上影响了伊希姆河流量。     

Comparison of the streamflow sensitivity to aridity index between the Danjiangkou Reservoir basin and Miyun Reservoir basin, China

The central route of China’s South-to-North Water Diversion Project would divert water from the Danjiangkou Reservoir basin (DRB) to Beijing beginning in the year 2014. The current main surface water source for Beijing is the Miyun Reservoir basin (MRB). The observed streamflows into the DRB and the MRB decreased significantly due to climatic variation and human activities from 1960 to 2005. The climate elasticity method is widely used to quantitatively separate the impacts of climatic variation and human activities on streamflow. One of the uncertainties of the method is that the impacts of changes in precipitation and potential evapotranspiration on streamflow are separated with the assumption that they are independent. However, precipitation and potential evapotranspiration are not totally independent. Aridity index, as the ratio between potential evapotranspiration and precipitation, could be considered as the representative indicator of climatic variation. In this study, the sensitivity of streamflow to aridity index is evaluated to assess the impact of climatic variation on streamflow in the DRB and the MRB. The result shows that streamflow in the MRB is more sensitive to climatic variation than that in the DRB. However, the effective impact of aridity index on streamflow is the product of the sensitivity and the change rate of aridity index. The attribution results show that change in aridity index contributed 68.8 % of the decrease in streamflow in the DRB while it contributed 31.5 % of the decrease in streamflow in the MRB. This indicated that the impact of climatic variation was the main reason of decrease in streamflow in the DRB while human activities such as increasing water consumption and land use change were the main reasons of decreasing streamflow in the MRB.     

2010—2100年淮河径流量变化情景预估

根据淮河流域14个气象站点1964—2007年观测降水量与温度数据和ECHAM5/MPI-OM模式在3种排放情景下对该流域2001—2100年的气候预估,利用人工神经网络模型预估淮河蚌埠站2010—2100年逐月径流量变化。计算结果表明:3种排放情景下2010—2100年淮河径流量年际变化幅度差异较大,SRES-A2情景总体处于波动上升趋势,其中2051—2085年上升趋势显著;SRES-A1B情景2024—2037年年平均流量显著降低;SRES-B1情景年平均流量的变率甚小。季节分析表明:春季径流量在2010—2100年变幅最小,距平百分率在-15.1%～18.6%之间小幅波动。夏季平均流量在2040年代前呈下降趋势,之后小幅波动上升。秋、冬季平均流量SRES-A2和SRES-A1B情景变幅显著,其中,秋季SRES-A2情景2060年代距平百分率下降达50.6%,为3种情景下各季节径流量降幅之最;冬季SRES-A1B情景2050年代其增幅达到54.7%,亦为上升幅度之最。     

近50年我国西部地区气象要素的变化特征

利用1951-2000年全国194站地面观测资料和高空观测资料,对近50年我国西部地区的气候变化特征进行分析。结果表明:从20世纪70年代开始,我国西部地区年平均气温呈上升趋势,其中河套区和新疆区气温上升最为明显,其次为青藏高原区和河西区,西南区气温增幅最不明显,地表温度变化与气温的变化基本同步,但地温变化要比气温变化更加剧烈一些。西南区的地温从70年代中期开始回升,但始终未达到50年代初期的水平,因此从线性变化上表现为下降趋势。西部地区除了河套区外,其他4个区的年平均降水量均增加,增加最明显的是新疆区和青藏高原区。我国整个西部地区年平均总云量和低云量均呈线性减少趋势,减少最明显的是西南区和河套区。在辐射变化上,我国西部总辐射呈减少趋势,青藏高原区减少最多;西南区的散射辐射呈增加趋势,其他4个区减少,其中新疆区和青藏高原区散射辐射减幅明显。散射辐射的大小与天空中云量和气溶胶含量的多少成正比,西南区散射辐射呈增加趋势,而总云量和低云量呈下降趋势,可以推测是气溶胶含量增加导致了散射辐射的增加。     

土地利用变化对长江流域气候及水文过程影响的敏感性研究

使用区域气候模式(RegCM3)和大尺度汇流模型(LRM), 研究土地利用/植被覆盖变化对长江流域气候及水文过程的影响。RegCM3嵌套于欧洲数值预报中心 (ECMWF) 再分析资料ERA40, 分别进行了中国区域在实际植被和理想植被分布情况下两个各15年 (1987～2001年) 时间长度的积分试验。随后, RegCM3 两个试验的输出径流结果分别用来驱动LRM, 研究土地利用/植被覆盖变化对长江流域河川径流的影响。研究结果指出, 中国当代土地利用变化对长江流域降水、蒸散发、径流深及河川径流等水文气候要素的改变较大, 对气温的改变并不明显。土地利用变化引起长江干流河川径流量在夏季(6～8月)有所增加, 并且越向下游增加幅度越大, 其中大通站径流量增加接近15%。总体而言, 土地利用改变加剧了长江流域夏季水循环过程, 使得夏季长江中下游地区降水增多, 径流增大。     

Streamflow trends and climate linkages in the Zagros Mountains,Iran

This paper examines trends in streamflow and their links with local climate in the Karkheh River and its major tributaries, which originate from the Zagros Mountains, Iran. Streamflow records from five mainstream stations for the period 1961–2001 were used to examine trends in a number of streamflow variables. The studied variables were mean annual and monthly flows, 1 and 7 days maximum and minimum flows, timing of the 1-day maxima and minima, and the number and duration of high and low flow pulses. Similarly, the precipitation and temperature data from seven climate stations for the period from 1950s to 2003 were used to examine trends in climatic variables and their correlation with the streamflow. The Spearman Rank test was used for the detection of trends and the correlation analysis was based on the Pearson method. The results reveal a number of significant trends in streamflow variables both increasing (e.g. December flows) and decreasing (e.g. May flows) for all stations. However, some trends were not spatially uniform. For example, decline in low flow characteristics were more significant in the upper parts of the basin, whereas increasing trends in floods and winter flows were noteworthy in the middle parts of the basin. Most of these trends could be attributed to precipitation changes. The results show that the decline in April and May precipitation causes the decline in the low flows while the increase in winter (particularly March) precipitation coupled with temperature changes lead to increase in the flood regime. The observed trends at the Jelogir station on the Karkheh River reflect the combined effect of the upstream catchments. The significant trends observed in a number of streamflow variables at Jelogir, 1-day maximum, December flow and low pulse count and duration, point to the changes in hydrological regime of the entire Karkheh River system and are attributed to the changes in climatic variables.     

四川西部夏季降水从1950s起的衰减趋势

Changing precipitation in the densely populated Sichuan basin may have a great impact on human life. This study analyzes the change in summer precipitation since 1951 over the western Sichuan basin, one of the regions of the heaviest rainfall in China, by using two datasets provided by the Chinese Meteorological Data Center. The results indicate that summer (from June to September) precipitation over the western Sichuan basin shows a significantly decreasing trend. The summer precipitation over this region has decreased by about 20% since the 1950s, with a rate of decrease of about 40 mm per decade.     

Effects of climate change on annual streamflow using climate elasticity in Poyang Lake Basin, China

Hydrological processes depend directly on climate conditions [e.g., precipitation, potential evapotranspiration (PE)] based on the water balance. This paper examines streamflow datasets at four hydrological stations and meteorological observations at 79 weather stations to reveal the streamflow changes and underlying drivers in four typical watersheds (Meigang, Saitang, Gaosha, and Xiashan) within Poyang Lake Basin from 1961 to 2000. Most of the less than 90th percentile of daily streamflow in each watershed increases significantly at different rates. As an important indicator of the seasonal changes in the streamflow, CT (the timing of the mass center of the streamflow) in each watershed shows a negligible change. The annual streamflow in each watershed increases at different rates, with a statistically significant trend (at the 5 % level) of 9.87 and 7.72 mm year^?1, respectively, in Meigang and Gaosha watersheds. Given the existence of interactions between precipitation and PE, the original climate elasticity of streamflow can not reflect the relationship of streamflow with precipitation and PE effectively. We modify this method and find the modified climate elasticity to be more accurate and reasonable using the correlation analysis. The analyses from the modified climate elasticity in the four watersheds show that a 10 % increase (decrease) in precipitation will increase (decrease) the annual streamflow by 14.1–16.3 %, while a 10 % increase (decrease) in PE will decrease (increase) the annual streamflow by ?10.2 to ?2.1 %. In addition, the modified climate elasticity is applied to estimate the contribution of annual precipitation and PE to the increasing annual streamflow in each watershed over the past 40 years. Our result suggests that the percentage attribution of the increasing precipitation is more than 59 % and the decreasing in PE is less than 41 %, indicating that the increasing precipitation is the major driving factor for the annual streamflow increase for each watershed.     

Separation of the impact of climate change and human activity on streamflow in the upper and middle reaches of the Taoer River,northeastern China

The Taoer River, a representative ecologically sensitive area in Northeast China, has undergone great climate changes and rapid social developments since 1961. Subsequently, a substantial alteration of the streamflow regime was observed and severe eco-environmental problems were becoming prominent. To provide decision makers the scientific basis for effective resource management and sound future planning, it is crucial to understand and assess the impacts of the climate variability and human activities on streamflow in this region. In this study, we combined an observation-based statistical analysis and physical modeling experiments to address this broad question. The Mann–Kendall and Sen’s slope were used to examine the trends and the moving t test was used to identify change points for the streamflow, precipitation, and potential evapotranspiration datasets. A statistically significant upward trend (α?=?5 %) was found for annual streamflow. An abrupt change point was identified in 1985 for the basin outlet station at Taonan. Accordingly, the streamflow was divided into baseline and changed period for attribution analysis. To investigate the impacts of climate change and human activities on annual streamflow, we applied a distributed hydrological model and six Budyko-type functions during the two periods. The results indicated that climate change and human activities accounted for about 45 and 55 % of the changes in streamflow, respectively.