基于黄河流域101个气象站点的实测气象数据和国际耦合模式比较计划第5阶段(coupled model intercomparison project phase 5,CMIP5)3种排放情景下的6个模型1961—2099年的降水和气温数据,采用等距离累积分布函数法(equidistant cumulati...基于黄河流域101个气象站点的实测气象数据和国际耦合模式比较计划第5阶段(coupled model intercomparison project phase 5,CMIP5)3种排放情景下的6个模型1961—2099年的降水和气温数据,采用等距离累积分布函数法(equidistant cumulative distribution function matching method,EDCDFm)进行统计降尺度;通过历史阶段(1961—2005年)实测站点数据对降尺度后的降水和气温进行精度评估;在此基础上,通过标准化降水指数(standardprecipitation index,SPI)对黄河流域气象干旱进行预估。结果表明,EDCDFm的降尺度方法能够明显提高气候模式所模拟的气温和降水精度,尤其对极值的模拟精度;黄河流域气象干旱的预估显示,3种气候情景下21世纪初的干旱情况相对于基准期均变得比较严重,但是世纪末的干旱程度均明显减轻,近期黄河流域的防旱工作形势仍然严峻。展开更多
The authors examine the spatial and temporal characteristics of the simulated Pacific Decadal Oscillation （PDO） in 109 historical （i.e. all forcings） simulations derived from 25 coupled models within CMIPS. Compar...The authors examine the spatial and temporal characteristics of the simulated Pacific Decadal Oscillation （PDO） in 109 historical （i.e. all forcings） simulations derived from 25 coupled models within CMIPS. Compared with observations, most simulations successfully simulate the observed PDO pattern and its teleconnections to the SSTs in the tropical and southern Pacific. BNU-ESM, CanESM2, CCSM4, CESM 1 -FASTCHEM, FGOALS-g2, GFDL CM3, MIROCS, and NorESM 1 -M show better performance. Compared with the temporal phases of the observed PDO in the twentieth century, only five simulations -- from CNRM^CMS, CSIRO Mk3o6.0, HadCM3, and IPSL-CMSA-LR -- simulate an evolution of the PDO similar to that derived from observation, which suggests that current coupled models can barely reproduce the observed phase shifting of the PDO. To capture characteristics of the observed PDO in the twentieth century, a requirement is that all the relevant external forcings are included in the models. How to add realistic oceanic initial states into the model may be another key point.展开更多
Based on observations and Coupled Model lntercomparison Project Phase 5 （CMIP5） results, multidecadal variations and trends in annual mean surface air temperature anomalies （SATa） at global, hemispheric, and hemis...Based on observations and Coupled Model lntercomparison Project Phase 5 （CMIP5） results, multidecadal variations and trends in annual mean surface air temperature anomalies （SATa） at global, hemispheric, and hemispheric land and ocean scales in the past and under the future scenarios of two representative concentration pathways （RCPs） are analyzed. Fifteen models are selected based on their performances in capturing the temporal variability, long-term trend, multidecadal variations, and trends in global annual mean SATa. Observational data analysis shows that the multidecadal variations in annual mean SATa of the land and ocean in the northern hemisphere （NH） and of the ocean in the southern hemisphere （SH） are similar to those of the global mean, showing an increase during the 1900-1944 and 1971-2000 periods, and flattening or even cooling during the 1945-1970 and 2001-2013 periods. These observed characteristics are basically reproduced by the models. However, SATa over SH land show an increase during the 1945-1970 period, which differs from the other hemispheric scales, and this feature is not captured well by the models. For the recent hiatus period （2001-2013）, the projected trends of BCC-CSM1-1-m, CMCC-CM, GFDL-ESM2M, and NorESM1-ME at the global and hemispheric scales are closest to the observations based on RCP4.5 and RCP8.5 scenarios, suggesting that these four models have better projection capability in SATa. Because these four models are better at simulating and projecting the multidecadal trends of SATa, they are selected to analyze future SATa variations at the global and hemispheric scales during the 2006-2099 period. The selected multi-model ensemble （MME） projected trends in annual mean SATa for the globe, NH, and SH under RCP4.5 （RCP8.5） are 0.17 （0.29） ℃, 0.22 （0.36） ℃, and 0.11 （0.23） ℃-decade-1 in the 21st century, respectively. These values are significantly lower than the projections of CMIP5 MME without model selection.展开更多
利用CMIP5的17个全球气候系统模式对500 hPa位势高度场的年代际回报结果,采用距平相关系数、均方根误差、平均绝对误差及连续等级概率评分4种指标,评估了贝叶斯模式平均（Bayesian model average,BMA）预报方法对东亚夏季环流的回报能力...利用CMIP5的17个全球气候系统模式对500 hPa位势高度场的年代际回报结果,采用距平相关系数、均方根误差、平均绝对误差及连续等级概率评分4种指标,评估了贝叶斯模式平均（Bayesian model average,BMA）预报方法对东亚夏季环流的回报能力,并与最优单模式MIROC5和多模式简单集合平均结果进行了比较。结果表明,BMA方法对东亚夏季500 hPa位势高度场的回报效果是最好的,优于最优单模式MIROC5和简单集合平均的回报结果。BMA模型能产生高集中度的概率密度函数,并包含了多模式集成回报不确定性的定量估计。此外,BMA方法对西太平洋副热带高压的年际变率也有较好的回报效果,对西太平洋副热带高压的预报,选取60~70%概率下的结果更为合理。展开更多
This study analyzed the interannual variability of sea surface temperature （SST） over the Pacific in the historical simulation and under the Representative Concentration Pathways （RCPs, including RCP4.5 and RCPS.5...This study analyzed the interannual variability of sea surface temperature （SST） over the Pacific in the historical simulation and under the Representative Concentration Pathways （RCPs, including RCP4.5 and RCPS.5） from 27 models archived in the Coupled Model Intercomparison Project Phase 5 （CMIPS）. Its association with the Asian-Pacific oscillation （APO） was also investigated.The evaluation results showed that the multi-model ensemble mean （MME） and most of the individual models perform well in reproducing the relatively stronger interannual variability of SST over the North Pacific and tropical eastern Pacific. They can also capture reasonably well the observed in-phase and out-of-phase relationships of the APO with the SST in the above two regions, respectively. Under the RCP4.5 and RCPS.5 scenarios, the interannual variability of the SST over the North Pacific and the tropical eastern Pacific is projected by the MME to be weakened during 2050-99 compared to 1950-99. The majority of the CMIP5 models show the same projection as the MME. Besides, the MME projection indicates that the present relationship between the APO and the SST over those two regions would still be dominant under both RCPs. However, considerable discrepancies exist in the changes of the relationships among the individual models.展开更多
The performances of CMIP5 atmospheric general circulation models （AGCMs） in simulating the western North Pacific subtropical high （WNPSH） in El Nino decaying summers are examined in this study. Results show that m...The performances of CMIP5 atmospheric general circulation models （AGCMs） in simulating the western North Pacific subtropical high （WNPSH） in El Nino decaying summers are examined in this study. Results show that most models can reproduce the spatial pattern of both climatological and anomalous circulation associated with the WNPSH in El Nino decaying summers. Most CMIP5 AGCMs can capture the westward shift of the WNPSH in El Nino decaying summers compared with the climatological location. With respect to the sub-seasonal variation of the WNPSH, the performances of these AGCMs in reproducing the northward jump of the WNPSH are better than simulating the eastward retreat of the WNPSH from July to August. Twenty-one out of twenty-two （20 out of 22） models can reasonably reproduce the northward jump of the WNPSH in El Nino decaying summers （climatology）, while only 7 out of 22 （8 out of 22） AGCMs can reasonably reproduce the eastward retreat of the WNPSH in El Nino decaying summers （climatology）. In addition, there is a close connection between the climatological WNPSH location bias and that in El Nino decaying summers.展开更多
The effective radiative forcing （ERF） and associated surface air temperature change over eastern China are estimated using multi-model results from CMIP5 （Coupled Model Intercomparison Project Phase 5）. The model ...The effective radiative forcing （ERF） and associated surface air temperature change over eastern China are estimated using multi-model results from CMIP5 （Coupled Model Intercomparison Project Phase 5）. The model results show that, relative to 1850, the multi-model and annual mean aerosol ERF for the year 2005 is -4.14 W m^-2 at the top of the atmosphere over eastern China （20°-45°N, 105°-122.5°E）. As a result of this ERF, the multi-model and annual mean surface air temperature change in eastern China during 1850-2005 is -1.05℃, leading to a climate sensitivity of 0.24℃/ （Wm^-2） in this region.展开更多
The downward surface shortwave radiation （DSSR） over the subtropical Asia-Pacific region simulated by the historical experiments of 15 CMIPS models is evaluated in this study.The simulated DSSR is compared against t...The downward surface shortwave radiation （DSSR） over the subtropical Asia-Pacific region simulated by the historical experiments of 15 CMIPS models is evaluated in this study.The simulated DSSR is compared against two satellite observational datasets, and the possible causes for the DSSR bias of the models are further investigated by dividing the subtropical Asia-Pacific region into five areas. Most of the CMIP5 models underestimate DSSR over the oceans, but overestimate DSSR over land. Aside from the Mediterranean-West Asia （MWA） and Central Asia （CA） areas, both the biases in annual and seasonal mean DSSR are well explained by the bias in surface shortwave cloud radiative forcing （CRF）, with an overestimation of the CRF effect over the subtropical North Pacific but an underestimation over other land regions. The effect of cloud plays a dominant role over the subtropical Asia-Pacific region, with relatively weaker influences over MWA and CA in boreal summer and fall.展开更多
文摘基于黄河流域101个气象站点的实测气象数据和国际耦合模式比较计划第5阶段(coupled model intercomparison project phase 5,CMIP5)3种排放情景下的6个模型1961—2099年的降水和气温数据,采用等距离累积分布函数法(equidistant cumulative distribution function matching method,EDCDFm)进行统计降尺度;通过历史阶段(1961—2005年)实测站点数据对降尺度后的降水和气温进行精度评估;在此基础上,通过标准化降水指数(standardprecipitation index,SPI)对黄河流域气象干旱进行预估。结果表明,EDCDFm的降尺度方法能够明显提高气候模式所模拟的气温和降水精度,尤其对极值的模拟精度;黄河流域气象干旱的预估显示,3种气候情景下21世纪初的干旱情况相对于基准期均变得比较严重,但是世纪末的干旱程度均明显减轻,近期黄河流域的防旱工作形势仍然严峻。
基金supported by the National Key R&D Program of China[grant number 2017YFA0603802]the National Natural Science Foundation of China[grant numbers 41661144005,41320104007,and 41575086]the CAS-PKU(Chinese Academy of Sciences-Peking University) Joint Research Program
文摘The authors examine the spatial and temporal characteristics of the simulated Pacific Decadal Oscillation （PDO） in 109 historical （i.e. all forcings） simulations derived from 25 coupled models within CMIPS. Compared with observations, most simulations successfully simulate the observed PDO pattern and its teleconnections to the SSTs in the tropical and southern Pacific. BNU-ESM, CanESM2, CCSM4, CESM 1 -FASTCHEM, FGOALS-g2, GFDL CM3, MIROCS, and NorESM 1 -M show better performance. Compared with the temporal phases of the observed PDO in the twentieth century, only five simulations -- from CNRM^CMS, CSIRO Mk3o6.0, HadCM3, and IPSL-CMSA-LR -- simulate an evolution of the PDO similar to that derived from observation, which suggests that current coupled models can barely reproduce the observed phase shifting of the PDO. To capture characteristics of the observed PDO in the twentieth century, a requirement is that all the relevant external forcings are included in the models. How to add realistic oceanic initial states into the model may be another key point.
基金This study was supported by National Key Research and Development Program of China （2016YFA0601801）, the State Key Program of National Natural Science Foundation of China （41530424）, National Program on Global Change and Air-Sea Interactions, State Oceanic Administration （SOA） （GASI-IPOVAI-03）, and the National Natural Science Foundation of China （41305121）. We sincerely thank two anonymous reviewers whose comments improved the paper.
文摘Based on observations and Coupled Model lntercomparison Project Phase 5 （CMIP5） results, multidecadal variations and trends in annual mean surface air temperature anomalies （SATa） at global, hemispheric, and hemispheric land and ocean scales in the past and under the future scenarios of two representative concentration pathways （RCPs） are analyzed. Fifteen models are selected based on their performances in capturing the temporal variability, long-term trend, multidecadal variations, and trends in global annual mean SATa. Observational data analysis shows that the multidecadal variations in annual mean SATa of the land and ocean in the northern hemisphere （NH） and of the ocean in the southern hemisphere （SH） are similar to those of the global mean, showing an increase during the 1900-1944 and 1971-2000 periods, and flattening or even cooling during the 1945-1970 and 2001-2013 periods. These observed characteristics are basically reproduced by the models. However, SATa over SH land show an increase during the 1945-1970 period, which differs from the other hemispheric scales, and this feature is not captured well by the models. For the recent hiatus period （2001-2013）, the projected trends of BCC-CSM1-1-m, CMCC-CM, GFDL-ESM2M, and NorESM1-ME at the global and hemispheric scales are closest to the observations based on RCP4.5 and RCP8.5 scenarios, suggesting that these four models have better projection capability in SATa. Because these four models are better at simulating and projecting the multidecadal trends of SATa, they are selected to analyze future SATa variations at the global and hemispheric scales during the 2006-2099 period. The selected multi-model ensemble （MME） projected trends in annual mean SATa for the globe, NH, and SH under RCP4.5 （RCP8.5） are 0.17 （0.29） ℃, 0.22 （0.36） ℃, and 0.11 （0.23） ℃-decade-1 in the 21st century, respectively. These values are significantly lower than the projections of CMIP5 MME without model selection.
文摘利用CMIP5的17个全球气候系统模式对500 hPa位势高度场的年代际回报结果,采用距平相关系数、均方根误差、平均绝对误差及连续等级概率评分4种指标,评估了贝叶斯模式平均（Bayesian model average,BMA）预报方法对东亚夏季环流的回报能力,并与最优单模式MIROC5和多模式简单集合平均结果进行了比较。结果表明,BMA方法对东亚夏季500 hPa位势高度场的回报效果是最好的,优于最优单模式MIROC5和简单集合平均的回报结果。BMA模型能产生高集中度的概率密度函数,并包含了多模式集成回报不确定性的定量估计。此外,BMA方法对西太平洋副热带高压的年际变率也有较好的回报效果,对西太平洋副热带高压的预报,选取60~70%概率下的结果更为合理。
基金jointly supported by the National Natural Science Foundation[grant number 41275078]the National Key Research and Development Program of China[grant number 2016YFA0600701]
文摘This study analyzed the interannual variability of sea surface temperature （SST） over the Pacific in the historical simulation and under the Representative Concentration Pathways （RCPs, including RCP4.5 and RCPS.5） from 27 models archived in the Coupled Model Intercomparison Project Phase 5 （CMIPS）. Its association with the Asian-Pacific oscillation （APO） was also investigated.The evaluation results showed that the multi-model ensemble mean （MME） and most of the individual models perform well in reproducing the relatively stronger interannual variability of SST over the North Pacific and tropical eastern Pacific. They can also capture reasonably well the observed in-phase and out-of-phase relationships of the APO with the SST in the above two regions, respectively. Under the RCP4.5 and RCPS.5 scenarios, the interannual variability of the SST over the North Pacific and the tropical eastern Pacific is projected by the MME to be weakened during 2050-99 compared to 1950-99. The majority of the CMIP5 models show the same projection as the MME. Besides, the MME projection indicates that the present relationship between the APO and the SST over those two regions would still be dominant under both RCPs. However, considerable discrepancies exist in the changes of the relationships among the individual models.
基金supported by the National Natural Science Foundation of China[grant numbers 41475052,41405058]China Postdoctoral Science Foundation[grant number 2015M571095]Strategic Priority Research Program of the Chinese Academy of Sciences[grant number XDA11010403]
文摘The performances of CMIP5 atmospheric general circulation models （AGCMs） in simulating the western North Pacific subtropical high （WNPSH） in El Nino decaying summers are examined in this study. Results show that most models can reproduce the spatial pattern of both climatological and anomalous circulation associated with the WNPSH in El Nino decaying summers. Most CMIP5 AGCMs can capture the westward shift of the WNPSH in El Nino decaying summers compared with the climatological location. With respect to the sub-seasonal variation of the WNPSH, the performances of these AGCMs in reproducing the northward jump of the WNPSH are better than simulating the eastward retreat of the WNPSH from July to August. Twenty-one out of twenty-two （20 out of 22） models can reasonably reproduce the northward jump of the WNPSH in El Nino decaying summers （climatology）, while only 7 out of 22 （8 out of 22） AGCMs can reasonably reproduce the eastward retreat of the WNPSH in El Nino decaying summers （climatology）. In addition, there is a close connection between the climatological WNPSH location bias and that in El Nino decaying summers.
基金supported by the National Basic Research Program of China[973 Program,grant number 2014CB441202]the National Natural Science Foundation of China[grant numbers41475137 and 91544219]
文摘The effective radiative forcing （ERF） and associated surface air temperature change over eastern China are estimated using multi-model results from CMIP5 （Coupled Model Intercomparison Project Phase 5）. The model results show that, relative to 1850, the multi-model and annual mean aerosol ERF for the year 2005 is -4.14 W m^-2 at the top of the atmosphere over eastern China （20°-45°N, 105°-122.5°E）. As a result of this ERF, the multi-model and annual mean surface air temperature change in eastern China during 1850-2005 is -1.05℃, leading to a climate sensitivity of 0.24℃/ （Wm^-2） in this region.
基金supported by the Special Public Welfare Research Fund of the China Meteorological Administration[grant number GYHY201406001]the Open Research Fund Program of Plateau Atmosphere and Environmental Key Laboratory of Sichuan Province[grant number PAEKL-2016-C4]
文摘The downward surface shortwave radiation （DSSR） over the subtropical Asia-Pacific region simulated by the historical experiments of 15 CMIPS models is evaluated in this study.The simulated DSSR is compared against two satellite observational datasets, and the possible causes for the DSSR bias of the models are further investigated by dividing the subtropical Asia-Pacific region into five areas. Most of the CMIP5 models underestimate DSSR over the oceans, but overestimate DSSR over land. Aside from the Mediterranean-West Asia （MWA） and Central Asia （CA） areas, both the biases in annual and seasonal mean DSSR are well explained by the bias in surface shortwave cloud radiative forcing （CRF）, with an overestimation of the CRF effect over the subtropical North Pacific but an underestimation over other land regions. The effect of cloud plays a dominant role over the subtropical Asia-Pacific region, with relatively weaker influences over MWA and CA in boreal summer and fall.
