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Poleward Expansion of the Hadley Circulation in cmip5 Simulations

Advances in Atmospheric Sciences 2013年第3期30卷 790-795页

作者：胡永云陶利军刘骥平 Laboratory for Climate and Ocean-Atmosphere Sciences Department of Atmospheric and Oceanic Sciences School of Physics Peking University State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics Institute of Atmospheric Physics Chinese Academy of Sciences

Observational analyses have demonstrated that the Hadley circulation has expanded poleward in recent decades. Important issues are what caused the widening of the Hadley circulation and whether the observed widening is related to anthropogenic forcing. In the present study, we use currently available simulations of the Coupled Model Intercomparison Project Phase-5 （cmip5） to analyze changes in the width of the Hadley circulation. It is found that cmip5 historical simulations with greenhouse gas （GHG） forcing generate a total widening of ,-0.15°±0.06°in latitude （10 yr）-1 for the period 1979-2005, and the widening in cmip5 historical simulations with all forcings is -0.17°± 0.06° per decade. Similar to that in cmip3, the simulated poleward expansion in cmip5 is much weaker than the observational reanalyses. In cmip5 projection simulations for the 21st century, magnitudes of widening of the Hadley circulation increase with radiative forcing. For the extreme projected radiative forcing of RCP8.5, the total annual-mean widening of the Hadley circulation is -0.27°±0.04° （10 yr）-1 in the 21st century. Although cmip5 underestimates observed poleward expansion of the Hadley circulation, the results of this study suggest that the observed trends in the width of the Hadley circulation are caused by anthropogenic forcing and that increasing GHGs play an important role in the observed poleward expansion of the Hadley circulation, in addition to other foreings emphasized in previous studies.

关键词： global warming Hadley circulation increasing greenhouse gases cmip5

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Intermodel Diversity in the Zonal Location of the Climatological East Asian Westerly Jet Core in Summer and Association with Rainfall over East Asia in cmip5 Models

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Advances in Atmospheric Sciences 2019年第6期36卷 614-622页

作者： Zhongda LIN Yuanhai FU Riyu LU State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics Institute of Atmospheric Physics Chinese Academy of Sciences Climate Change Research Center Institute of Atmospheric Physics Chinese Academy of Sciences

The East Asian westerly jet(EAJ), an important midlatitude circulation of the East Asian summer monsoon system,plays a crucial role in affecting summer rainfall over East Asia. The multimodel ensemble of current coupled models can generally capture the intensity and location of the climatological summer EAJ. However, individual models still exhibit large discrepancies. This study investigates the intermodel diversity in the longitudinal location of the simulated summer EAJ climatology in the present-day climate and its implications for rainfall over East Asia based on 20 cmip5 models. The results show that the zonal location of the simulated EAJ core is located over either the midlatitude Asian continent or the western North Pacific(WNP) in different models. The zonal shift of the EAJ core depicts a major intermodel diversity of the simulated EAJ climatology. The westward retreat of the EAJ core is related to a warmer mid–upper tropospheric temperature in the midlatitudes, with a southwest–northeast tilt extending from Southwest Asia to Northeast Asia and the northern North Pacific, induced partially by the simulated stronger rainfall climatology over South Asia. The zonal shift of the EAJ core has some implications for the summer rainfall climatology, with stronger rainfall over the East Asian continent and weaker rainfall over the subtropical WNP in relation to the westward-located EAJ core.

关键词： zonal location East Asian westerly jet summer rainfall intermodel diversity cmip5

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Performance of cmip5 Models in the Simulation of Climate Characteristics of Synoptic Patterns over East Asia

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Journal of Meteorological Research 2015年第4期29卷 594-607页

作者：王永弟江志红陈威霖 Key Laboratory of Meteorological Disaster of Ministry of Education Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters Nanjing University of Information Science & Technology School of Geography and Remote Sensing Nanjing University of Information Science & Technology

The evolution of daily synoptic weather patterns is the main driver of day-to-day weather change. These patterns are generally associated with changes in temperature, precipitation, etc., especially during extreme weathers. Evaluating the ability of climate models to reproduce the frequency and intensity of daily synoptic patterns is essential for increasing confidence in future projections. In this study, we investigated the ability of 34 global climate models （GCMs） included in the Coupled Model Intercomparison Project Phase 5 （cmip5） to simulate synoptic patterns over East Asia and their evolution features in winter and summer. Daily synoptic patterns in sea level pressure and their occurrence frequencies were identified by using an objective clustering algorithm, self-organizing maps （SOMs）. The evaluation consists of correlating the frequencies of these patterns in the 34 cmip5 models with the frequencies in the NCEP reanalysis during the baseline period of 1980-1999. The results illustrated that most of these models were able to reproduce the synoptic patterns of the NCEP reanalysis. In addition, the frequencies of temporal sea level pressure （SLP） anomaly patterns were reproduced by most of the models over the baseline period, but the frequencies of spatial SLP anomaly patterns were only reproduced by a few GCMs. Overall, the models performed better in summer than in winter. Comprehensive evaluation shows that the four top-performing models for both winter and summer are bcc-csml-l-m, NorESM1-M, MRI-CGCM3, and CCSM4. They show good performance in simulating the daily synoptic patterns in SLP and in reproducing their occurrence frequencies. The results showed that the SOM was an effective tool for differentiating characteristics of synoptic circulation patterns and for evaluating the ability of climate models to simulate the frequency of daily synoptic patterns. The results can also help users to choose a better model for future climate projection and downscal

关键词： cmip5 climate model evaluation self-organizing maps atmospheric circulation pattern

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Projections of the Advance in the Start of the Growing Season during the 21st Century Based on cmip5 Simulations

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Advances in Atmospheric Sciences 2015年第6期32卷 831-838页

作者： XIA Jiangjiang YAN Zhongwei JIA Gensuo ZENG Heqing Philip Douglas JONES ZHOU Wen ZHANG Anzhi Key Laboratory of Regional Climate-Environment for East Asia Institute of Atmospheric PhysicsChinese Academy of Sciences Ministry of Environmental Protection of Jiuzhaigou Country Climatic Research Unit University of East Anglia Center of Excellence for Climate Change Research and Department of Meteorology King Abdulaziz University Guy Carpenter Asia-Pacific Climate Impact Centre School of Energy and EnvironmentCity University of Hong Kong

It is well-known that global warming due to anthropogenic atmospheric greenhouse effects advanced the start of the vegetation growing season （SOS） across the globe during the 20th century. Projections of further changes in the SOS for the 21st century under certain emissions scenarios （Representative Concentration Pathways, RCPs） are useful for improving understanding of the consequences of global warming. In this study, we first evaluate a linear relationship between the SOS （defined using the normalized difference vegetation index） and the April temperature for most land areas of the Northern Hemisphere for 1982-2008. Based on this relationship and the ensemble projection of April temperature under RCPs from the latest state-of-the-art global coupled climate models, we show the possible changes in the SOS for most of the land areas of the Northern Hemisphere during the 21st century. By around 2040-59, the SOS will have advanced by -4.7 days under RCP2.6, -8.4 days under RCP4.5, and -10.1 days under RCPS.5, relative to 1985-2004. By 2080-99, it will have advanced by -4.3 days under RCP2.6, -11.3 days under RCP4.5, and -21.6 days under RCP8.5. The geographic pattern of SOS advance is considerably dependent on that of the temperature sensitivity of the SOS. The larger the temperature sensitivity, the larger the date-shift-rate of the SOS.

关键词： start of growing season (SOS) normalized difference vegetation index (NDVI) temperature sensitivity Repre-sentative Concentration Pathways (RCPs) cmip5

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Analyses of Extreme Climate Events over China Based on cmip5 Historical and Future Simulations

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Advances in Atmospheric Sciences 2014年第5期31卷 1209-1220页

作者： YANG Shili FENG Jinming DONG Wenjie CHOU Jieming State Key Laboratory of Earth Surface Process and Resource Ecology Beijing Normal University Key Laboratory of Regional Climate–Environment for East Asia Institute of Atmospheric PhysicsChinese Academy of Sciences College of Global Change and Earth System Science Beijing Normal University

Based on observations and 12 simulations from Coupled Model Intercomparison Project Phase 5 （cmip5） models, cli- matic extremes and their changes over China in the past and under the future scenarios of three Representative Concentration Pathways （RCPs） are analyzed. In observations, frost days （FD） and low-temperature threshold days （TN10P） show a de- creasing trend, and summer days （SU）, high-temperature threshold days （TX90P）, heavy precipitation days （R20）, and the contribution of heavy precipitation days （P95T） show an increasing trend. Most models are able to simulate the main char- acteristics of most extreme indices. In particular, the mean FD and TX90P are reproduced the best, and the basic trends of FD, TN10P, SU and TX90P are represented. For the FD and SU indexes, most models show good ability in capturing the spatial differences between the mean state of the periods 1986--2005 and 1961-80; however, for other indices, the simulation abilities for spatial disparity are less satisfactory and need to be improved. Under the high emissions scenario of RCP8.5, the century-scale linear changes of the multi-model ensemble （MME） for FD, SU, TN10P, TX90P, R20 and P95T are -46.9, 46.0, -27.1, 175.4, and 2.9 days, and 9.9%, respectively; and the spatial change scope for each index is consistent with the emissions intensity. Due to the complexities of physical process pararneterizations and the limitation of forcing data, great uncertainty still exists with respect to the simulation of climatic extremes.

关键词： extreme climate China cmip5 RCPs

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Simulation of the Equatorially Asymmetric Mode of the Hadley Circulation in cmip5 Models

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Advances in Atmospheric Sciences 2015年第8期32卷 1129-1142页

作者： FENG Juan LI Jianping ZHU Jianlei LI Fei SUN Cheng College of Global Change and Earth System Science Beijing Normal University State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics Institute of Atmospheric Physics Chinese Academy of Sciences Joint Center for Global Change Studies Department of Lower Atmosphere Observation Research Institute of Atmospheric PhysicsChinese Academy of Sciences

The tropical Hadley circulation （HC） plays an important role in influencing the climate in the tropics and extra-tropics. The realism of the climatological characteristics, spatial structure, and temporal evolution of the long-term variation of the principal mode of the annual mean HC （i.e., the equatorially asymmetric mode, EAM） was examined in model simulations from the Coupled Model Intercomparison Project Phase 5 （cmip5）. The results showed that all the models are moderately successful in capturing the HC＇s climatological features, including the spatial pattern, meridional extent, and intensity, but not the spatial or temporal variation of the EAM. The possible reasons for the poor simulation of the long-term variability of the EAM were explored. None of the models can successfully capture the differences in the warming rate between the tropical Southern Hemisphere （SH） and Northern Hemisphere （NH）, which is considered to be an important driver for the variation of the AM. Most of the models produce a faster warming in the NH than in the SH, which is the reverse of the observed trend. This leads to a reversed trend in the meridional gradient between the SH and NH, and contributes to the poor simulation of EAM variability. Thus, this aspect of the models should be improved to provide better simulations of the variability of the HC. This study suggests a possible reason for the poor simulation of the HC, which may be helpful for improving the skill of the cmip5 models in the future.

关键词： tropical Hadley circulation equatorially asymmetric mode cmip5 sea surface temperature

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Assessment of Indices of Temperature Extremes Simulated by Multiple cmip5 Models over China

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Advances in Atmospheric Sciences 2015年第8期32卷 1077-1091页

作者： DONG Siyan XU Ying ZHOU Botao SHI Ying National Climate Center China Meteorological Administration

Given that climate extremes in China might have serious regional and global consequences, an increasing number of studies are examining temperature extremes in China using the Coupled Model Intercomparison Project Phase 5 （cmip5） models. This paper investigates recent changes in temperature extremes in China using 25 state-of-the-art global climate models participating in cmip5. Thirteen indices that represent extreme temperature events were chosen and derived by daily maximum and minimum temperatures, including those representing the intensity （absolute indices and threshold indices）, duration （duration indices）, and frequency （percentile indices） of extreme temperature. The overall performance of each model is summarized by a ＂portrait＂ diagram based on relative root-mean-square error, which is the RMSE relative to the median RMSE of all models, revealing the multi-model ensemble simulation to be better than individual model for most indices. Compared with observations, the models are able to capture the main features of the spatial distribution of extreme temperature during 1986-2005. Overall, the cmip5 models are able to depict the observed indices well, and the spatial structure of the ensemble result is better for threshold indices than frequency indices. The spread amongst the cmip5 models in different subregions for intensity indices is small and the median cmip5 is close to observations; however, for the duration and frequency indices there can be wide disagreement regarding the change between models and observations in some regions. The model ensemble also performs well in reproducing the observational trend of temperature extremes. All absolute indices increase over China during 1961-2005.

关键词： temperature extremes China cmip5 model evaluation

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Evaluation of cmip5 Climate Models in Simulating 1979–2005 Oceanic Latent Heat Flux over the Pacific

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Advances in Atmospheric Sciences 2015年第12期32卷 1603-1616页

作者： CAO Ning REN Baohua ZHENG Jianqiu School of Earth and Space Sciences University of Science and Technology of China Key Laboratory of Meteorological Disaster of Ministry of Education Nanjing University of Information Science and Technology

The climatological mean state, seasonal variation and long-term upward trend of 1979-2005 latent heat flux （LHF） in historical runs of 14 coupled general circulation models from cmip5 （Coupled Model Intercomparison Project Phase 5） are evaluated against OAFlux （Objectively Analyzed air-sea Fluxes） data. Inter-model diversity of these models in simulating the annual mean climatological LHF is discussed. Results show that the models can capture the climatological LHF fairly well, but the amplitudes are generally overestimated. Model-simulated seasonal variations of LHF match well with observations with overestimated amplitudes. The possible origins of these biases are wind speed biases in the cmip5 models. Inter-model diversity analysis shows that the overall stronger or weaker LHF over the tropical and subtropical Pacific region, and the meridional variability of LHF, are the two most notable diversities of the cmip5 models. Regression analysis indicates that the inter-model diversity may come from the diversity of simulated SST and near-surface atmospheric specific humidity. Comparing the observed long-term upward trend, the trends of LHF and wind speed are largely underestimated, while trends of SST and air specific humidity are grossly overestimated, which may be the origins of the model biases in reproducing the trend of LHF.

关键词： model evaluation climatology trend latent heat flux cmip5

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Eastern equatorial Pacific SST seasonal cycle in global climate models: from cmip5 to cmip6

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Acta Oceanologica Sinica 2020年第7期39卷 50-60页

作者： Zhenya Song Hailong Liu Xingrong Chen First Institute of Oceanography Ministry of Natural ResourcesQingdao 266061China Laboratory for Regional Oceanography and Numerical Modeling Pilot National Laboratory for Marine Science and Technology(Qingdao)Qingdao 266237China School of Oceanography Shanghai Jiaotong UniversityShanghai 200240China National Marine Environmental Forecasting Center Ministry of Natural ResourcesBeijing 100081China

The sea surface temperature(SST)seasonal cycle in the eastern equatorial Pacific(EEP)plays an important role in the El Nino–Southern Oscillation(ENSO)***,the reasonable simulation of SST seasonal cycle in the EEP is still a challenge for climate *** this paper,we evaluated the performance of 17 cmip6 climate models in simulating the seasonal cycle in the EEP and compared them with 43 cmip5 climate *** general,only CESM2 and SAM0-UNICON are able to successfully capture the annual mean SST characteristics,and the results showed that cmip6 models have no fundamental improvement in the model annual mean *** the seasonal cycle,14 out of 17 climate models are able to represent the major characteristics of the observed SST annual *** spring,12 models capture the 1–2 months leading the eastern equatorial Pacific region 1(EP1;5°S–5°N,110°–85°W)against the eastern equatorial Pacific region 2(EP2;5°S–5°N,140°–110°W).In autumn,only two models,GISS-E2-G and SAM0-UNICON,correctly show that the EP1 and EP2 SSTs vary in *** the cmip6 MME SST simulation in EP1,both the cold bias along the equator in the warm phase and the warm bias in the cold phase lead to a weaker annual SST cycle in the CGCMs,which is similar to the cmip5 ***,both the seasonal cold bias and warm bias are considerably decreased for cmip6,which leads the annual SST cycle to more closely reflect the *** the cmip6 MME SST simulation in EP2,the amplitude is similar to the observed value due to the quasi-constant cold bias throughout the year,although the cold bias is clearly improved after August compared with cmip5 ***,although SAM0-UNICON successfully captured the seasonal cycle characteristics in the EEP and the improvement from cmip5 to cmip6 in simulating EEP SST is clear,the fundamental climate models simulated biases still exist.

关键词： cmip5 cmip6 eastern equatorial Pacific SST seasonal cycle

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Evaluating the Formation Mechanisms of the Equatorial Pacific SST Warming Pattern in cmip5 Models

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Advances in Atmospheric Sciences 2016年第4期33卷 433-441页

作者： Jun YING Ping HUANG Ronghui HUANG Center for Monsoon System Research Institute of Atmospheric Physics Chinese Academy of Sciences Beijing 100190 University of Chinese Academy of Sciences Beijing 100049 Joint Center for Global Change Studies Beijing 100875

Based on the historical and RCP8.5 runs of the multi-model ensemble of 32 models participating in cmip5, the present study evaluates the formation mechanisms for the patterns of changes in equatorial Pacific SST under global warming. Two features with complex formation processes, the zonal E1 Nifio-like pattern and the meridional equatorial peak warm- ing （EPW）, are investigated. The climatological evaporation is the main contributor to the E1 Nifio-like pattern, while the ocean dynamical thermostat effect plays a comparable negative role. The cloud-shortwave-radiation-SST feedback and the weakened Walker circulation play a small positive role in the E1 Nifio-like pattern. The processes associated with ocean dynamics are confined to the equator. The climatological evaporation is also the dominant contributor to the EPW pattern, as suggested in previous studies. However, the effects of some processes are inconsistent with previous studies. For example, changes in the zonal heat advection due to the weakened Walker circulation have a remarkable positive contribution to the EPW pattern, and changes in the shortwave radiation play a negative role in the EPW pattern.

关键词： global warming equatorial Pacific SST warming pattern multi-model ensemble cmip5

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