2050年前长江流域极端降水预估

Daily maximum rainfall(R1D)was higher in the Jialing River basin,the Taihu Lake area and the mid-lower main stream section of the Yangtze River basin in the 1990s,and there was a good relationship between ECHAM5/MPI-OM model simulation and the observed data about extreme precipitation(R1D).Under the IPCC SRES A2,A1B,and B1 scenarios,R1Ds are all projected to be in increasing trends in the upper Yangtze River basin during 2001-2050,and R1D shows a more significant increasing tendency under the A2 scenario when compared with the A1B scenario before 2020.With respect to the middle and lower Yangtze River basin,an increasing tendency is projected before 2025,and since then the increasing tendency will become insignificant.There might be more floods to the south of the Yangtze River and more droughts to the north in the next decades.     

2050年前长江流域极端降水预估

20世纪90年代长江流域日最大降水增加主要出现在长江以南地区和金沙江流域,ECHAM5/MPI-OM模型也大致模拟出了这种趋势。在IPCC给出的3种不同的排放情景下,2000-2050年长江上游日最大降水均有上升趋势,2020年前A2情景下日最大降水最大,A1B最小;长江中下游日最大降水在2025年之前均有明显上升趋势,之后略有下降,波动较大。长江流域未来日最大降水增多的区域可能主要出现在长江以南地区,而极端降水减少的区域可能出现在长江以北地区。     

全球增暖背景下2050年前长江流域气候趋势预估

根据ECHAM5/ MPI-OM模式对长江流域21世纪前半叶气候变化的预估数据,分析了全流域、上游地区和中下游地区未来气候变化趋势。结果表明,长江流域气温将持续升高,尤其7-8月升温趋势明显,年平均温度升高最大幅度为2.60℃;全流域7月降水将增加,8月降水有减少趋势,未来夏季降水更加集中,不仅会增加洪涝灾害的发生机率,也有可能导致旱灾的发生。     

Simulation of extreme precipitation indices in the Yangtze River basin by using statistical downscaling method (SDSM)

In this study, the applicability of the statistical downscaling model (SDSM) in modeling five extreme precipitation indices including R10 (no. of days with precipitation ≥10?mm?day^?1), SDI (simple daily intensity), CDD (maximum number of consecutive dry days), R1d (maximum 1-day precipitation total) and R5d (maximum 5-day precipitation total) in the Yangtze River basin, China was investigated. The investigation mainly includes the calibration and validation of SDSM model on downscaling daily precipitation, the validation of modeling extreme precipitation indices using independent period of the NCEP reanalysis data, and the projection of future regional scenarios of extreme precipitation indices. The results showed that: (1) there existed good relationship between the observed and simulated extreme precipitation indices during validation period of 1991–2000, the amount and the change pattern of extreme precipitation indices could be reasonably simulated by SDSM. (2) Under both scenarios A2 and B2, during the projection period of 2010–2099, the changes of annual mean extreme precipitation indices in the Yangtze River basin would be not obvious in 2020s; while slightly increase in the 2050s; and significant increase in the 2080s as compared to the mean values of the base period. The summer might be the more distinct season with more projected increase of each extreme precipitation indices than in other seasons. And (3) there would be distinctive spatial distribution differences for the change of annual mean extreme precipitation indices in the river basin, but the most of Yangtze River basin would be dominated by the increasing trend.     

2050年前长江流域地表水资源变化趋势

利用ECHAM5/MPI-OM气候模式预估2001-2050年长江流域不同排放情景（SRES-A2,A1B,B1）下径流深的变化,分析了长江流域地表水资源量的时空变化特征。结果表明：3种排放情景下长江流域多年平均地表水资源量相差不大,但不同排放情景下年际变化特征较为复杂,且变化趋势有所不同。其中,A2高排放情景下地表水资源量呈缓慢减小的趋势,A1B中等排放情景下变化趋势不明显,B1低排放情景下呈相对最为显著的增加趋势。地表水资源量年代际变化波动幅度也较大,2001-2030年3种情景下地表水资源量总体呈现下降特征,但从2030年起,则均表现出不同程度的增加,最高增幅达7.47%,其中尤以夏季和冬季增加显著。模式预估长江流域未来水资源量仍保持目前水平,水资源空间分布不均匀特征仍较为突出。     

2050年前长江流域地表水资源变化趋势

 利用ECHAM5/MPI-OM气候模式预估2001-2050年长江流域不同排放情景（SRES-A2,A1B,B1）下径流深的变化,分析了长江流域地表水资源量的时空变化特征。结果表明：3种排放情景下长江流域多年平均地表水资源量相差不大,但不同排放情景下年际变化特征较为复杂,且变化趋势有所不同。其中,A2高排放情景下地表水资源量呈缓慢减小的趋势,A1B中等排放情景下变化趋势不明显,B1低排放情景下呈相对最为显著的增加趋势。地表水资源量年代际变化波动幅度也较大,2001-2030年3种情景下地表水资源量总体呈现下降特征,但从2030年起,则均表现出不同程度的增加,最高增幅达7.47%,其中尤以夏季和冬季增加显著。模式预估长江流域未来水资源量仍保持目前水平,水资源空间分布不均匀特征仍较为突出。     

长江流域径流对全球升温1.5℃与2.0℃的响应

全球变暖影响着以流域径流要素为主导的水文水资源系统的变化。长江流域未来水资源量的时空分布对长江大保护与长江经济带的发展意义重大。为探究全球升温1.5℃和2.0℃对长江流域径流变化的影响,使用基于偏差校正的气候模式集合数据驱动两参数月水量平衡模型,比较两种升温情景下径流量的响应差异。结果表明：基于偏差校正的气候模式集合数据可以较好地代表长江流域历史时期（1976—2005年）的年平均降水和年平均蒸散发情势。两参数月水量平衡模型与参数区域化方法相结合能较好地模拟长江流域各子流域的月径流量。升温1.5℃时,无论是年径流量还是季节径流量均呈上升趋势,与历史时期相比,50%以上三级子流域的增幅超过5%;升温2.0℃时,增幅超过8%。这表明升温2.0℃情景下长江流域水资源量将进一步增加。相对于历史时期,升温1.5℃与2.0℃情景下长江流域北部降水量增幅较大;径流量增幅分布格局基本与降水量一致。汉江流域是全流域径流量增幅最显著的区域。     

Assessment of CMIP3 climate models and projected changes of precipitation and temperature in the Yangtze River Basin, China

The projected changes of precipitation and temperature in the Yangtze River Basin in the 20th Century from 20 models of the CMIP3 (phase 3 of the Coupled Model Inter-comparison Project) dataset are analyzed based on the observed precipitation and temperature data of 147 meteorological stations in the Yangtze River Basin. The results show that all models tend to underestimate the annual mean temperature over the Yangtze River Basin, and to overestimate the annual mean precipitation. The temporal changes of simulated annual mean precipitation and temperature are broadly comparable with the observations, but with large variability among the results of the models. Most of the models can reproduce maximum precipitation during the monsoon season, while all models tend to underestimate the mean temperature of each month over the Yangtze River Basin. The Taylor diagram shows that the differences between modeled and observed temperature are relatively smaller as compared to differences in precipitation. For a detailed investigation of regional characteristics of climate change in the Yangtze River Basin during 2011–2050, the multi-model ensembles produced by an upgraded REA method are carried out for more reliable projections. The projected precipitation and temperature show large spatial variability in the Yangtze River Basin. Mean precipitation will increase under the A1B and B1 scenarios and decrease under the A2 scenario, with linear trends ranging from ?21 to 28.5?mm/decade. Increasing mean temperature can be found in all scenarios with linear trends ranging from 0.15 to 0.48°C/decade. Grids in the head region of the Jingshajiang catchment show distinct increasing trends for all scenarios. Some physical processes associated with precipitation are not well represented in the models.     

Atmospheric moisture budget and floods in the Yangtze River basin, China

In this paper, we explored the trends of the atmospheric moisture budget, precipitation, and streamflow in summer during 1961 to 2005 and possible correlations between them by using the linear regression method in the Yangtze River basin, China. The results indicate that: (1) increasing tendencies can be detected in the atmospheric moisture budget, precipitation and streamflow in the Yangtze River basin; however, the significant increasing trends occur only in the atmospheric moisture budget and precipitation in the middle and lower Yangtze River basin; (2) both the ratio of summer moisture budget to annual moisture budget and the ratio of summer precipitation to annual precipitation exhibit a significant increasing trend in the Yangtze River basin. The ratio of summer streamflow to annual streamflow is in a significant increasing trend in Hankou station. Significant increasing summer precipitation can be taken as the major controlling factor responsible for the higher probability of flood hazard occurrences in the Yangtze River basin. The consecutively increasing summer precipitation is largely due to the consistently increasing moisture budget; (3) the zonal geopotential height anomaly between 1991 and 2005 and 1961 and 1990 is higher from the south to the north, which to a large degree, limits the northward propagation of the summer monsoon to north China. As a result, the summer moisture budget increases in the middle and lower Yangtze River basin, which leads to more summer precipitation. This paper sheds light on the changing properties of precipitation and streamflow and possible underlying causes, which will be greatly helpful for better understanding of the changes of precipitation and streamflow in the Yangtze River basin.     

气候变化对长江上游径流影响预估

利用第五次国际耦合模式比较计划(CMIP5)中5个气候模式在3种典型浓度路径(RCPs)下的预估结果驱动SWAT水文模型,预估了21世纪气候变化对长江上游年径流量、季节分配以及极端径流的影响。结果表明：预估的长江上游平均气温呈显著上升趋势,21世纪末较当前(1986—2005年)升高1.5~5.5℃,降水总体呈增加趋势,在21世纪30年代后高于当前气候平均值,21世纪末相对于当前增加5%~15%。流域内气候变化存在明显空间差异,金沙江和岷沱江流域气温升高和降水增加幅度均大于流域平均值。预估的长江上游年径流量及各月平均径流均有增加趋势,在21世纪30年代后高于当前多年平均值,21世纪中期增加4%~8%,21世纪末增加10%~15%。预估的径流年内分布的均匀性有所增加,但年际变化明显增大,极端旱涝事件的频率和强度明显增加。预估的各子流域径流变化对气候变化的响应也存在差异,金沙江和岷沱江流域年径流量、年际变化和年内分布变化小,对气候变化的响应表现为低敏感;嘉陵江流域、乌江流域和长江上游干流径流增加幅度大,同时极端丰枯出现的频率和程度增加显著,是气候变化响应的敏感区域。     

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。     

1960-2005年长江流域降水极值概率分布特征

Based on the daily observational precipitation data of 147 stations in the Yangtze River basin for 1960-2005,and the projected daily data of 79 grids from ECHAM5/MPI-OM in the 20th century,time series of precipitation extremes which contain annual maximum(AM)and Munger index(MI)were constructed.The distribution feature of precipitation extremes was analyzed based on the two index series.Research results show that(1)the intensity and probability of extreme heavy precipitation are higher in the middle Mintuo River sub-catchment,the Dongting Lake area,the mid-lower main stream section of the Yangtze River,and the southeastern Poyang Lake sub-catchment;whereas,the intensity and probability of drought events are higher in the mid-lower Jinsha River sub-catchment and the Jialing River sub-catchment;(2)compared with observational data,the averaged value of AM is higher but the deviation coefficient is lower in projected data,and the center of precipitation extremes moves northwards;(3)in spite of certain differences in the spatial distributions of observed and projected precipitation extremes,by applying General Extreme Value(GEV)and Wakeby(WAK)models with the method of L-Moment Estimator(LME)to the precipitation extremes,it is proved that WAK can simulate the probability distribution of precipitation extremes calculated from both observed and projected data quite well.The WAK could be an important function for estimating the precipitation extreme events in the Yangtze River basin under future climatic scenarios.     

Observed changes of temperature extremes during 1960�C2005 in China: natural or human-induced variations?

The purpose of this study was to statistically examine changes of surface air temperature in time and space and to analyze two factors potentially influencing air temperature changes in China, i.e., urbanization and net solar radiation. Trends within the temperature series were detected by using Mann-Kendall trend test technique. The scientific problem this study expected to address was that what could be the role of human activities in the changes of temperature extremes. Other influencing factors such as net solar radiation were also discussed. The results of this study indicated that: (1) increasing temperature was observed mainly in the northeast and northwest China; (2) different behaviors were identified in the changes of maximum and minimum temperature respectively. Maximum temperature seemed to be more influenced by urbanization, which could be due to increasing urban albedo, aerosol, and air pollutions in the urbanized areas. Minimum temperature was subject to influences of variations of net solar radiation; (3) not significant increasing and even decreasing temperature extremes in the Yangtze River basin and the regions south to the Yangtze River basin could be the consequences of higher relative humidity as a result of increasing precipitation; (4) the entire China was dominated by increasing minimum temperature. Thus, we can say that the warming process of China was reflected mainly by increasing minimum temperature. In addition, consistently increasing temperature was found in the upper reaches of the Yellow River basin, the Yangtze River basin, which have the potential to enhance the melting of permafrost in these areas. This may trigger new ecological problems and raise new challenges for the river basin scale water resource management.     

Probability Distribution of Precipitation Extremes over the Yangtze River Basin

 Based on the daily observational precipitation data of 147 stations in the Yangtze River basin for 1960-2005, and the projected daily data of 79 grids from ECHAM5/MPI-OM in the 20th century, time series of precipitation extremes which contain annual maximum (AM) and Munger index (MI) were constructed. The distribution feature of precipitation extremes was analyzed based on the two index series. Research results show that (1) the intensity and probability of extreme heavy precipitation are higher in the middle Mintuo River sub-catchment, the Dongting Lake area, the mid-lower main stream section of the Yangtze River, and the southeastern Poyang Lake sub-catchment; whereas, the intensity and probability of drought events are higher in the mid-lower Jinsha River sub-catchment and the Jialing River sub-catchment; (2) compared with observational data, the averaged value of AM is higher but the deviation coefficient is lower in projected data, and the center of precipitation extremes moves northwards; (3) in spite of certain differences in the spatial distributions of observed and projected precipitation extremes, by applying General Extreme Value (GEV) and Wakeby (WAK) models with the method of L-Moment Estimator (LME) to the precipitation extremes, it is proved that WAK can simulate the probability distribution of precipitation extremes calculated from both observed and projected data quite well. The WAK could be an important function for estimating the precipitation extreme events in the Yangtze River basin under future climatic scenarios.     

人类活动对1961～2016年长江流域降水变化的可能影响

人类活动造成的温室气体浓度增加对气候变化的加剧做出了贡献,降水作为重要的气象要素和水循环组成部分,人类活动对其时空变化特征的影响也是当下研究的重要课题。本文以长江流域为例,利用1961～2016年CN05.1逐日降水数据和20世纪气候检测归因计划（C20C+D&A Project）中CAM5.1-1degree模式的逐日降水结果,分析了人类活动对长江流域年降水量及三个极端降水指数时空变化的影响。结果表明:包含人类活动及自然强迫因素的现实情景（All-Hist）的模拟结果与观测结果较为相近。All-Hist情景下的多试验集合平均结果对长江流域降水的模拟能力较为可靠。通过对比两种情景下模拟的长江流域降水量时空变化特征发现:考虑人类活动影响后,长江流域平均降水相对于仅考虑自然强迫情景下时呈现减少趋势,且减少趋势随时间推移加剧;极端降水受人类活动的影响随时间呈现出的增加趋势有所削弱;对平均降水及极端降水变化趋势的影响存在空间差异性,其中受人类活动影响最严重的是上游中部、东南部及中下游东南部地区,均呈现减少趋势;但在长江上游西南部极端降水受人类活动影响显著增加,需要加强该区域洪涝预防工作。另外,人类活动对平均降水的减少贡献最大的时段为2000～2009年,影响最明显季节为秋冬两季;人类活动对极端降水的影响与降水的极端程度成正相关,降水极端性越强,受人类活动影响的变化程度更大,且空间分布上的差异性也更加显著。     

1960年以来长江流域太阳总辐射的时空变化

基于长江流域147个站点的气象数据,利用气候学计算方法估算1960年以来的太阳总辐射数据,运用线性回归和相关分析等方法,探讨1960年以来太阳总辐射在长江流域的时空变化特征,并分析太阳总辐射的影响因子.结果表明:太阳总辐射在整个长江流域(除去上游源头区金沙江流域)自东向西递减,且上游地区变化波动大,中下游地区下降趋势显著;自1960年以来太阳总辐射在长江流域呈现下降趋势,1990年以后开始呈现上升趋势;近50a来太阳总辐射的减少趋势与云量和大气水汽含量没有显著相关性.     

CWRF模式对长江流域极端降水气候事件的模拟能力评估

基于1980—2016年长江流域站点观测降水,评估了CWRF区域气候模式对长江流域面雨量和极端降水气候事件的模拟能力.结果表明:CWRF模式能较好地再现1980—2016年长江流域及不同分区降水空间分布及月/季面雨量年际变率,且在冬、春季表现较好,夏、秋季次之.CWRF模式对长江流域面雨量存在系统性高估,对面雨量的模拟...     

Multimodel ensemble projections of future climate extreme changes in the Haihe River Basin,China

Exploring the characteristic of the extreme climatic events, especially future projection is considerably important in assessing the impacts of climatic change on hydrology and water resources system. We investigate the future patterns of climate extremes (2001–2099) in the Haihe River Basin (HRB) derived from Coupled General Circulation Model (CGCM) multimodel ensemble projections using the Bayesian Model Average (BMA) approach, under a range of emission scenarios. The extremes are depicted by three extreme temperature indices (i.e., frost days (FD), growing season length (GSL), and T _min >90th percentile (TN90)) and five extreme precipitation indices (i.e., consecutive dry days (CDD), precipitation ≥10 mm (R10), maximum 5-day precipitation total (R5D), precipitation >95th percentile (R95T), and simple daily intensity index (SDII)). The results indicate frost days display negative trend over the HRB in the 21st century, particularly in the southern basin. Moreover, a greater season length and more frequent warm nights are also projected in the basin. The decreasing CDD, together with the increasing R10, R5D, R95T, and SDII in the 21st century indicate that the extreme precipitation events will increase in their intensity and frequency in the basin. Meanwhile, the changes of all eight extremes climate indices under A2 and A1B scenarios are more pronounced than in B1. The results will be of practical significance in mitigation of the detrimental effects of variations of climatic extremes and improve the regional strategy for water resource and eco-environment management, particularly for the HRB characterized by the severe water shortages and fragile ecological environment.     

1951-2006年黄河和长江流域雨涝变化分析

 根据1951-2006年黄河和长江流域雨涝灾害灾情统计资料,分析了两个流域雨涝灾害发生频率的时空分布特征,结果表明：近50 a以来,特别是20世纪80年代以来,受气候变化影响,黄河和长江流域雨涝灾害不断增加,农作物受灾、成灾面积呈增加趋势,损失日趋严重,且长江流域受雨涝灾害影响范围较大,灾害发生频率大于黄河流域。受暴雨影响,夏季两个流域雨涝发生频率最高、范围最广。20世纪80年代末以来,黄河流域雨涝灾害增加趋势较为明显,而长江流域80年代初雨涝受灾面积和成灾面积显著增加。两个流域雨涝灾害的受灾率均自上游至下游逐渐增加,其中长江流域中下游地区受雨涝灾害影响较大。     

Climate Simulation and Future Projection of Precipitation and the Water Vapor Budget in the Haihe River Basin

The climatological characteristics of precipitation and the water vapor budget in the Haihe River basin (HRB) are analyzed using daily observations at 740 stations in China in 1951-2007 and the 4-time daily ERA40 reanalysis data in 1958-2001. The results show that precipitation and surface air temperature present significant interannual and interdecadal variability, with cold and wet conditions before the 1970s but warm and dry conditions after the 1980s. Precipitation has reduced substantially since the 1990s, with a continued increase of surface air temperature. The total column water vapor has also reduced remarkably since the late 1970s. The multi-model ensemble from the Fourth Assessment Report (AR4) of the Intergovernmental Panel on Climate Change (IPCC) has capably simulated the 20th century climate features and successfully reproduced the spatial patterns of precipitation and temperature. Unfortunately, the models do not reproduce the interdecadal changes. Based on these results, future projections of the climate in the HRB are discussed under the IPCC Special Report on Emissions Scenarios (SRES) B1, A1B, and A2. The results show that precipitation is expected to increase in the 21st century, with substantial interannual fluctuations relative to the models’ baseline climatology. A weak increasing trend in precipitation is projected before the 2040s, followed by an abrupt increase after the 2040s, especially in winter. Precipitation is projected to increase by 10%-18% by the end of the 21st century. Due to the persistent warming of surface air temperature, water vapor content in the lower troposphere is projected to increase. Relative humidity will decrease in the mid-lower troposphere but increase in the upper troposphere. On the other hand, precipitation minus evaporation remains positive throughout the 21st century. Based on these projection results, the HRB region is expected to get wetter in the 21st century due to global warming.