Projected change in extreme rainfall events in China by the end of the 21st century using CMIP5 models

Projection of future climate changes and their regional impact is critical for long-term planning at the national and regional levels aimed at adaptation and mitigation. This study assesses the future changes in precipitation in China and the associated atmospheric circulation patterns using the Couple Model Intercomparison Project 5 Phase (CMIP5) simulations under the RCP4.5 and RCP8.5 scenarios. The results consistently indicate that the annual precipitation in China is projected to significantly increase at the end of the 21st century compared to the present-day levels. The number of days and the intensity of medium rain, large rain and heavy rain are obviously increased, while the number of trace rain days is projected to decrease over the entire area of China. Further analysis indicates that the significant increase of annual precipitation in Northwest China is primarily due to the increase of light rain and the increases in North and Northeast China are primarily due to the increase of medium rain. In the region of southern China, the increases of large rain and heavy rain play an important role in the increase of annual precipitation, while light rain events play a negative role. Analysis of the changes in atmospheric circulation indicates that the East Asian summer monsoon circulation is projected to be considerably stronger, and the local atmospheric stratification is projected to be more unstable, all of which provide a background benefit for the increase of precipitation and extreme rainfall events in China under global warming scenarios.     

Simulation of the future change of East Asian monsoon climate using the IPCC SRES A2 and B2 scenarios

In this paper, we applied the newest emission scenarios of the sulfur and greenhouse gases, i.e. Intergovernmental Panel on Climate Change (IPCC) Special Report on Emission Scenarios (SRES) A2 and B2 scenarios, to investigating the change of the East Asian climate in the last three decades of the 21st century with an atmosphere-ocean coupled general circulation model. The global warming enlarges the land-sea thermal contrast and, hence, enhances (reduces) the East Asian summer (winter) monsoon circulation. The precipitation from the Yangtze and Huaihe river valley to North China increases significantly. In particular, the strong rainfall increase over North China implies that the East Asian rainy area would expand northward. In addition, from the southeastern coastal area to North China, the rainfall would increase significantly in September, implying that the rainy period of the East Asian monsoon would be prolonged about one month. In July, August and September, the interannual variability of the precipitation enhances evidently over North China, meaning a risk of flooding in the future.     

East Asian monsoon change for the 21st century: Results of CMIP3 and CMIP5 models

Forty-two climate models participating in the Coupled Model Intercomparison Project Phases 3 and 5 were first evaluated in terms of their ability to simulate the present climatology of the East Asian winter (December-February) and summer (June-August) monsoons. The East Asian winter and summer monsoon changes over the 21st century were then projected using the results of 31 and 29 reliable climate models under the Special Report on Emissions Scenarios (SRES) mid-range A1B scenario or the Representative Concentration Pathways (RCP) mid-low-range RCP4.5 scenario, respectively. Results showed that the East Asian winter monsoon changes little over time as a whole relative to the reference period 1980-1999. Regionally, it weakens (strengthens) north (south) of about 25°N in East Asia, which results from atmospheric circulation changes over the western North Pacific and Northeast Asia owing to the weakening and northward shift of the Aleutian Low, and from decreased north- west-southeast thermal and sea level pressure differences across Northeast Asia. In summer, monsoon strengthens slightly in East China over the 21st century as a consequence of an increased land-sea thermal contrast between the East Asian continent and the adjacent western North Pacific and South China Sea.     

西江流域气候变化下未来时期降雨的时空变化

珠江流域是岭南地区最大的流域,西江流域为珠江的主要支流.西江流域未来时期年最大降雨与年均降雨的变化会影响未来时期的极端洪水与水资源短缺情况,但是相关研究较少.该研究基于国际多模型比较计划ISIMIP2b数据,对西江流域未来时期年最大降雨与年均降雨进行研究.研究发现,年最大与年均降雨在RCP 8.5与RCP 4.5场景下...     

基于不同气候变化情景的东江流域水资源量预测研究

采用半分布式水文模型HSPF,结合1978-1998年东江流域实测气象数据和5个气候模式在3种RCP气候情景(RCP8.5,RCP4.5,RCP2.6)下基准期(1960-2000年)和未来时期(2020-2070年)降水、蒸发情景模拟结果,在对东江流域径流模拟检验基础上,对2020-2070年东江流域水资源量做了深入分析。结果表明,HSPF模型能很好模拟东江流域年、月径流以及洪水期径流变化,博罗站的NASH系数均超过0.81,PBIAS低于10%,RSR低于0.45;所选取气候模式能很好的反映研究流域气象数据在年内分布情况。对未来气候和东江流域水资源量模拟结果表明:1 2020-2070年不同气候变化情景下东江流域降水及蒸发量在RCP2.6和RCP4.5情景下均呈上升趋势,而在RCP8.5情景下,东江流域蒸发量则呈现下降趋势;2未来东江流域多年月均径流量呈增加趋势;3未来东江流域不同频率下的洪水和枯水流量均呈不同程度的增长。相对于基准期,未来时期的洪水天数呈增长趋势,洪水灾害有加剧态势。     

亚欧大陆经向热力差异对亚洲季风的影响Ⅰ:与东亚冬季风的关系

 通过对亚欧大陆不同季节热力变化的对比分析,发现亚欧大陆冬、春季有明显的经向热力差异,夏、秋季存在准纬向的热力差异.进一步分析还发现大陆冬季经向热力差异与东亚冬季风有很好的正相关关系,即热力差异指数越大(小),则东亚冬季风越强(弱);在经向热力异常发生的同时,洋面热力状况也显著不同,从而导致东亚地区不同区域间海陆热力对比发生变化,引起降水分布的不同.     

华北夏季降水年代际变化与东亚夏季风、大气环流异常

利用华北夏季降水资料和NCEP/NCAR再分析资料,对华北夏季降水、东亚夏季风年代际变化特征及大气环流异常进行研究,发现一些有意义的结果:华北夏季降水变化存在明显的8a、18a周期,东亚夏季风变化18a、28a周期性比较明显,二者年代际变化特征明显,但华北夏季降水变化和东亚夏季风变化的周期不完全一致.华北夏季降水量变化在60年代中期发生了突变,东亚夏季风变化在70年代中期发生了突变.华北夏季降水与东亚夏季风变化存在很好的相关关系,强夏季风年,华北夏季降水一般偏多,弱夏季风年,华北夏季降水一般偏少,但又不完全一致.东亚夏季风减弱是造成华北夏季降水减少的一个重要因素,但不是唯一因素,华北夏季降水减少还与环流异常密切相关.在地面上,青臧高原地区、华北地区气温下降造成华北低压系统活动减少,不利于降水.在850 hPa层上,东亚中纬度的西南季风和副热带高压南部的偏东风、西北部的西南风异常减弱,使得西南气流输送水汽很多难以到达30°N以北的地区,而副热带高压西部外围偏东南、偏南气流输送到华北地区的水汽也大量减少,水汽不足造成华北夏季降水偏少.在500 hPa高度场上,80年代欧亚遥相关型表现与50年代相反,变为欧洲( )、乌拉尔山(-)、中亚( )形势,这种环流使得乌拉尔山高压脊减弱,贝加尔湖至青藏高原高空槽变浅,纬向环流表现突出,不利于冷暖空气南北交换.同时在500 hPa气温场上,80年代,西伯利亚至青藏高原西北部的冷槽明显东移南压到蒙古至华北地区,锋区位于华北以东以南位置,使得华北地区冷暖空气交汇减少,降水也因此减少.华北夏季降水减少是由于东亚夏季风减弱和大气环流异常造成的.     

Southern Hemisphere mean zonal wind in upper troposphere and East Asian summer monsoon circulation

1 Introduction Variability of the East Asian summer monsoon (EASM) has been detected by considering roles of El Nino and Southern Oscillation (ENSO) cycle, snow cover over Eurasia and Tibetan Plateau, and signals from the soil (namely, the soil temperatur…     

未来气候变化情景下湖北省极端降水的人口暴露分析

基于湖北省历史灾情数据构建受灾率与雨强、人均GDP的回归模型,选取RCP4.5和RCP8.5情景下的日降水数据及对应SSPs路径下的人口和GDP资料,分析了湖北省不同时期极端降水事件、人口及人口暴露度的时空分布特征及变化情况.结果表明:受灾率与雨强、人均GDP都存在着显著的相关性(P <0.01).通过构建受灾率模型,使之能够更加准确地刻画人口暴露情况.湖北省的极端降水事件在空间上自东南向西北递减,且整体强度随时间变化而增加;湖北省人口总数整体东密西疏,SSP3路径始终高于SSP2;人均GDP分布由武汉向四周递减,随时间快速增长,SSP2路径下的值始终大于SSP3;湖北省极端降水人口暴露度的高值中心,随时间变化向南向东发展,同时由于人均GDP的快速增长,设防水平大幅提升,人口总量减少,暴露总量不断减少,RCP8.5情景下,极端降水人口暴露度和暴露总量始终高于RCP4.5情景,并在未来中期时差距加大.     

未来气候变化情景下中国北方农牧交错带脆弱性评估

基于中国地面降水和气温0.5°×0.5°格点数据集以及区域协同降尺度试验东亚地区项目组RCP4.5和RCP8.5情景下未来气候预估数据,对中国北方农牧交错带1980—2100年的气候脆弱性进行模拟和分析。结果表明,北方农牧交错带气候脆弱性在未来的100年中整体上呈现增大的趋势,特别是2050年后,增大速度进一步加剧,到21世纪末,几乎整个北方农牧交错带都表现出明显脆弱性。从宁夏中卫到呼和浩特北部一带,脆弱性形势较为严峻,而大兴安岭北部地区脆弱性程度较低。     

Identifying the northernmost summer monsoon location in East Asia

An integrated index which can be used to indicate the advance of subtropical summer monsoon in East Asia has been proposed in this paper.The index was comhined by three variables including precipitation,wind and pseudo-equivalent potential tempera- ture.The northernmost summer monsoon location(NSML)was identified by using this index annually.It was found that the NSML ex- perienced an interdecadal shift in the period 1977—1979 based on the annual index analysis from 1961 to 2001.A comparison of the NSML with other four summer monsoon indices has also been made.The result showed that the NSML could well represent the interan- nual and interdecadal variability of summer monsoon precipitation in North China(beyond 35°N),while other four indices could well indi- cate the precipitation anomalies of East Asian summer monsoon along the Yangtze River valley(around 30°N).     

Uncertainty in crossing time of 2 °C warming threshold over China

The 2 °C warming target has been used widely in global and regional climate change research. Previous studies have shown large uncertainties in the time when surface air temperature (SAT) change over China will reach 2 °C relative to the pre-industrial era. To understand the uncertainties, we analyzed the projected SAT in the twenty-first century using 40 state-of-the-art climate models under two Representative Concentration Pathways (RCP4.5 and RCP8.5) from the Coupled Model Intercomparison Project Phase 5. The 2 °C threshold-crossing time (TCT) of SAT averaged across China was around 2033 and 2029 for RCP4.5 and RCP8.5, respectively. Considering a ±1σ range of intermodel SAT change, the upper and lower bounds of the 2 °C TCT could differ by about 25 years or even more. Uncertainty in the projected SAT and the warming rate around the TCT are the two main factors responsible for the TCT uncertainty. The former is determined by the climate sensitivity represented by the global mean surface temperature response. About 45 % of the intermodel variance of the projected 2 °C TCT for averaged SAT over China can be explained by climate sensitivity across the models, which is contributed mainly by central and southern China. In a climate more sensitive to CO₂ forcing, stronger greenhouse effect, less stratus cloud over the East Asian monsoon region, and less snow cover on the Tibetan Plateau result in increased downward longwave radiation, increased shortwave radiation, and decreased shortwave radiation reflected by the surface, respectively, all of which may advance the TCT.     

Interdecadal change of summer precipitation over Eastern China around the late-1990s and associated circulation anomalies, internal dynamical causes

Observational study indicated that the summer precipitation over Eastern China experienced a notable interdecadal change around the late-1990s. Accompanying this interdecadal change, the dominant mode of anomalous precipitation switched from a meridional triple pattern to a dipole pattern, showing a "south-flood-north-drought" structure (with the exception of the Yangtze River Valley). This interdecadal change of summer precipitation over Eastern China was associated with circulation anomalies in the middle/upper troposphere over East Asia, such as changes in winds and corresponding divergence, vertical motion and moisture transportation (divergence), which all exhibit remarkable meridional dipole structures. Furthermore, on the internal dynamic and thermodynamic aspects, the present study investigated the influence of the midtroposphere zonal and meridional flow changes over East Asia on the interdecadal change around the late-1990s. Results suggested that, during 1999-2010, the East Asia subtropical westerly jet weakened and shifted poleward, forming a meridional dipole feature in anomalous zonal flow. This anomalous zonal flow, on one hand, induced changes in three teleconnection patterns over the Eurasian continent, namely the "Silk Road" pattern along the subtropical upper troposphere westerly jet, the East Asia/Pacific (EAP) pattern along the East Asian coast, and the Eurasia (EU) pattern along the polar jet; on the other hand, it brought about cold advection over Northern China, and warm advection over Southern China in the mid-troposphere. Through these two ways, the changes in the zonal flow induced descent over Northern China and ascent over Southern China, which resulted in the anomalous "south-flood-north-drought" feature of the summer precipitation over Eastern China during 1999-2010.     

Interannual variability of Mascarene high and Australian high and their influences on summer rainfall over East Asia

Based on the reanalysis data from NCEP/NCAR and other observational data,interannual variability of Mascarene high(MH) and Australian high(AH) from 1970 to 1999 is examined.It is shown that interannual variability of MH is dominated by the Antarctic oscillation(AAO),when the circumpolar low in the high southern latitudes deepens,the intensity of MH will be intensified.On the other hand,AH is correlated by AAO as well as EI Nino and South Oscillation(ENSO),the intensity of AH will be intensified when EI Nino occurs.Both correlation analysis and case study demonstrate that summer rainfall over East Asia is closely related to MH and AH.When MH intensifies from boreal spring to summer (i.e.from austral autumn to winter),there is more rainfall over regions from the Yangtze River valley to Japan,in contrast,less rainfall is found over southern China and western Pacific to the east of Taiwan,and most of regions in mid-latitudes of East Asia.Compared with MH,the effect of AH on summer rainfall in East Asia is limited to localized regions,there is more rainfall over southern China with the intensification of AH.The results in this study show that AAO is a strong signal on interannual timescale,which plays an important role in summer rainfall over East Asia.This discovery is of real importance to revealingt the physical mechanism of interannual variability of East Asian summer monsoon and prediction of summer precipitation in China.     

气候变化对中国北方季风区生态系统总初级生产量的影响评价

利用中国北方季风区121个地表气象观测站2000-2013年逐日气温和降水资料及MODIS遥感8天平均总初级生产量数据(MOD17A2), 分别建立了14年内8天累积平均、最低、最高气温和降雨量与累积总初级生产量的线性气候相关模型。基于模型所得区间的阈值和参数, 计算区域模式RSM本底时期10年(1996-2005年)及未来 10年(2041-2050年)两种排放情景RCP4.5和RCP8.5下, 森林、草地和农田生态系统总初级生产量累积开始日期、累积时期、累积结束日期及累积速率变化, 分析平均、最高、最低气温和降水量变化对总初级生产量累积的影响, 并综合评价气候变化对生态系统总初级生产量累积的影响。结果表明: 平均气温和最低气温对总初级生产量的模拟精度高于最高气温和降雨量; 总初级生产量累积开始和结束日期对4 类气候因子的变化均较敏感, 而累积时期和累积速率仅对平均气温和最高气温的变化较敏感; 未来气候变化将延长累积时期, 增加累积速率, 并提高总初级生产量。     

Modeling impacts of East Asian Ocean-Land thermal contrast on spring southwesterly winds and rainfall in eastern China

Using the National Centers for Environmental Prediction–National Center for Atmospheric Research （NCEP–NCAR） reanalysis dataset, the NOAA’s Climate Prediction Center’s merged analysis of precipitation, and the MM5v3 Meso-scale Model, the impacts of surface temperature differences between the East Asian land and its adjacent oceans on spring southwesterly winds and rainfall over eastern China are studied. The modeling results show that the temperature differences exert strong influence on the occurrence of the southwesterly winds and rainfall over southern China and their northward advances. When surface temperature increases over the land and decreases over the oceans, the temperature gradient with a winter feature earlier changes toward the gradient with a summer feature. Both the low-pressure system east of the Tibetan Plateau and the subtropical high-pressure system over the western Pacific strengthen, accompanying with the strengthening of the lower-tropospheric southwesterly winds over eastern China. Accordingly, the upward motion increases over the Yangtze-Huaihe River （YHR） valleys and decreases over southern China, leading to an increase of spring rainfall over the YHR valleys and a decrease over southern China. Thus, the rain belt over eastern China appears over the YHR valleys but not over southern China. Under a weaker condition of the spring thermal contrast, the rain belt does not occur over eastern China. When the spring thermal contrast pronouncedly strengthens, the rain belt over southern China may advance northward into the YHR valleys during spring, though there is no onset of the tropical monsoon over the South China Sea. This forms a rain belt similar to that of the YHR valleys during the summer Meiyu period.     

Reduction of the East Asian winter monsoon interannual variability after the mid-1980s and possible cause

The East Asian winter monsoon (EAWM) consists of subsystems such as the Siberian high, Aleutian low, East Asian trough, low-level northerly wind and high-level East Asian jet stream. It is revealed that the interannual variation of the EAWM-related atmospheric circulation has exhibited an obvious weakening since the mid-1980s. During 1956-1980, significant negative correlations between the EAWM and sea surface temperature are observed in the oceans along the east coast of East Asia, accompanied by significant positive correlations in the western Warm Pool. However, the significant interannual relationship in the previous period is found to have been disrupted during 1986-2010. Further analysis reveals that the Arctic Oscillation after the mid-1980s tends to suppress the interannual variability of the EAWM. In addition, it was found that the large-scale warming after the mid-1980s is favorable to reduce the land-sea thermal contrast variability on both the interdecadal and interannual time scales.     

A comparison of the Medieval Warm Period, Little Ice Age and 20th century warming simulated by the FGOALS climate system model

To compare differences among the Medieval Warm Period (MWP), Little Ice Age (LIA), and 20th century global warming (20CW), six sets of transient and equilibrium simulations were generated using the climate system model FGOALS_gl. This model was developed by the State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics, Institute of Atmospheric Physics, Chinese Academy of Sciences. The results indicate that MWP warming is evident on a global scale, except for at mid-latitudes of the North Pacific. However, the magnitude of the warming is weaker than that in the 20th century. The warming in the high latitudes of the Northern Hemisphere is stronger than that in the Southern Hemisphere. The LIA cooling is also evident on a global scale, with a strong cooling over the high Eurasian continent, while the cooling center is over the Arctic domain. Both the MWP and the 20CW experiments exhibit the strongest warming anomalies in the middle troposphere around 200?C300 hPa, but the cooling center of the LIA experiment is seen in the polar surface of the Northern Hemisphere. A comparison of model simulation against the reconstruction indicates that model??s performance in simulating the surface air temperature changes during the warm periods is better than that during the cold periods. The consistencies between model and reconstruction in lower latitudes are better than those in high latitudes. Comparison of the inter-annual variability mode of East Asian summer monsoon (EASM) rainfall during the MWP, LIA and 20CW reveals a similar rainfall anomalies pattern. However, the time spectra of the principal component during the three typical periods of the last millennium are different, and the quasi-biannual oscillation is more evident during the two warm periods. At a centennial time scale, the external mode of the EASM variability driven by the changes of effective solar radiation is determined by the changes of large scale land-sea thermal contrast. The rainfall anomalies over the east of 110°E exhibit a meridional homogeneous change pattern, which is different from the meridional out-of-phase change of rainfall anomalies associated with the internal mode.     

Large-scale low-frequency rainfall regimes and their transition modes in summertime over China

It is well known that the predictable period of daily weather is generally within 2-3 weeks, so spatio-temporal mean predictands have to be employed in the monthly, seasonal, and annual predictions. At present, rainfall patterns (RPs)[1-5] are the key for…     

初夏南亚高压中心经向位置年际变化的一个关键预测信号

基于欧洲中期天气预报中心的ERA-interim再分析资料,应用统计和动力诊断方法,分析了初夏南亚高压（SAH）中心位置年际变化规律及其与青藏高原东南部热源异常的联系.结果显示：初夏SAH中心位置具有显著的准6 a变化特征,但仅有其经向位置与初春青藏高原东南部（SETP）大气潜热活动存在显著的负相关关系;与偏强的初春SETP潜热活动相联系,异常的西风出现在青藏高原的南侧20°N附近,偏西风异常北侧的正涡度异常及其南侧的负涡度异常,加强了青藏高原附近的异常气旋以及印度次大陆半岛及印度洋上空的异常反气旋,这一异常环流形势可以从初春一直维持到初夏,不利于SAH向北移动,最终导致初夏SAH中心位置偏南;反之,初春SETP异常偏弱的潜热活动将以大致相反的物理过程,最终使得初夏SAH中心位置偏北.冬末春初的SETP潜热活动是预报初夏SAH中心经向位置年际变化的一个关键信号.