Pronounced climatic differences occur over subtropical South China(SC)and tropical South China Sea(SCS)and understanding the key cloud-radiation characteristics is essential to simulating East Asian climate.This study...Pronounced climatic differences occur over subtropical South China(SC)and tropical South China Sea(SCS)and understanding the key cloud-radiation characteristics is essential to simulating East Asian climate.This study investigated cloud fractions and cloud radiative effects(CREs)over SC and SCS simulated by CMIP6 atmospheric models.Remarkable differences in cloud-radiation characteristics appeared over these two regions.In observations,considerable amounts of low-middle level clouds and cloud radiative cooling effect appeared over SC.In contrast,high clouds prevailed over SCS,where longwave and shortwave CREs offset each other,resulting in a weaker net cloud radiative effect(NCRE).The models underestimated NCRE over SC mainly due to weaker shortwave CRE and less cloud fractions.Conversely,most models overestimated NCRE over SCS because of stronger shortwave CRE and weaker longwave CRE.Regional CREs were closely linked to their dominant cloud fractions.Both observations and simulations showed a negative spatial correlation between total(low)cloud fraction and shortwave CRE over SC,especially in winter,and exhibited a positive correlation between high cloud fraction and longwave CRE over these two regions.Compared with SCS,most models overestimated the spatial correlation between low(high)cloud fraction and SWCRE(LWCRE)over SC,with larger bias ranges among models,indicating the exaggerated cloud radiative cooling(warming)effect caused by low(high)clouds.Moreover,most models struggled to describe regional ascent and its connection with CREs over SC while they can better reproduce these connections over SCS.This study further suggests that reasonable circulation conditions are crucial to simulating well cloud-radiation characteristics over the East Asian regions.展开更多
Against the backdrop of climate change,the activity of tropical cyclones(TCs)has captured widespread attention.Observational datasets indicate a declining trend in the genesis longitude of western North Pacific(WNP)TC...Against the backdrop of climate change,the activity of tropical cyclones(TCs)has captured widespread attention.Observational datasets indicate a declining trend in the genesis longitude of western North Pacific(WNP)TCs.This study investigates the zonal changes of WNP TCs with CMIP6-HighResMIP models.These models capture the genesis density of WNP TCs fairly well.The results reveal a westward shift in TC genesis longitude.This trend is associated with the significant reduction in the TC frequency over the southeastern WNP.The study also discusses changes in large-scale circulation patterns and the impact of the strengthening Pacific Walker circulation.展开更多
In the northern Tarim River Basin,the Weigan River Basin is a critical endorheic system characterized by extreme aridity,where drought poses a major natural hazard to agricultural production and ecological stability.T...In the northern Tarim River Basin,the Weigan River Basin is a critical endorheic system characterized by extreme aridity,where drought poses a major natural hazard to agricultural production and ecological stability.This study assessed the future evolution of drought under climate change by employing the standardized moisture anomaly index(SZI)on the basis of multi-model the Coupled Model Intercomparison Project Phase 6(CMIP6)simulations under historical conditions(1970–2014)and future scenarios(shared socioeconomic pathway(SSP)1-2.6,SSP2-4.5,SSP3-7.0 and SSP5-8.5 for 2015–2100).The results show that precipitation–evapotranspiration anomalies are projected to first decline but then increase over time,with increased fluctuations and uncertainty under high-emission scenarios(SSP5-8.5).These trends indicate intensifying drought risks and reveal a strong influence of emission pathways on regional water cycling.Temporal analysis of SZI indicates a transition from wetting to drying under lowand medium-emission pathways(SSP1-2.6 and SSP2-4.5),whereas high-emission scenarios are characterized by persistent drying and increased variability.The significant lower-tail dependence(0.271)observed under SSP2-4.5 and SSP5-8.5 suggests that extreme droughts may be subject to nonlinear co-amplification across scenarios.The frequency of moderate and more severe drought events is expected to increase substantially,especially under SSP5-8.5,where drought occurrence is predicted to extend into spring and autumn and become more evenly distributed throughout the year.Spatially,drought duration shows significant positive autocorrelation across all scenarios,with hot spots consistently concentrated in the southern and southeastern regions of the basin.Random forest analysis,interpreted as association-based pattern attribution,indicates that meteorological variables(precipitation and potential evapotranspiration(PET))make the greatest contributions to the hot spot pattern,followed by topography and soil moisture.Among land use categories,farmland generally shows higher drought sensitivity than other land use types,as reflected by its relative contribution patterns across scenarios.The spatial pattern of drought is statistically structured by climatic forcing,surface conditions,and soil moisture status,reflecting their coupled associations with hot spot occurrence.In addition,a drought spatial uncertainty index was constructed from multi-scenario hot spot maps,revealing spatially heterogeneous structural variability throughout the basin.Correlation analysis further highlights strong internal couplings among environmental variables(e.g.,elevation-linked hydroclimatic gradients and grassland–bare soil contrasts).These findings offer a scientific basis for developing region-specific drought monitoring and adaptation strategies under future climate change conditions.展开更多
Precipitation and surface temperature are two important quantities whose variations are closely related through various physical processes. In the present study, we evaluated the precipitation-surface temperature （P-...Precipitation and surface temperature are two important quantities whose variations are closely related through various physical processes. In the present study, we evaluated the precipitation-surface temperature （P-T） relationship in 17 climate models involved in the Coupled Model Intercomparison Project Phase 5 （CMIP5） for the IPCC Assessment Report version 5. Most models performed reasonably well at simulat- ing the large-scale features of the P-T correlation distribution. Based on the pattern correlation of the P-T correlation distribution, the models performed better in November-December-January-February-March （NDJFM） than in May-June-July-August-September （MJJAS） except for the mid-latitudes of the North- ern Hemisphere, and the performance was generally better over the land than over the ocean. Seasonal dependence was more obvious over the land than over the ocean and was more obvious over the mid- and high-latitudes than over the tropics. All of the models appear to have had difficulty capturing the P-T correlation distribution over the mid-latitudes of the Southern Hemisphere in MJJAS. The spatial variabil- ity of the P-T correlation in the models was overestimated compared to observations. This overestimation tended to be larger over the land than over the ocean and larger over the mid- and high-latitudes than over the tropics. Based on analyses of selected model ensemble simulations, the spread of the P-T correlation among the ensemble members appears to have been small. While the performance in the P-T correlation provides a general direction for future improvement of climate models, the specific reasons for the discrep- ancies between models and observations remain to be revealed with detailed and comprehensive evaluations in various aspects.展开更多
Future potential sea level change in the South China Sea （SCS） is estimated by using 24 CMIP5 models under different representative concentration pathway （RCP） scenarios. By the end of the 21st century （2081–210...Future potential sea level change in the South China Sea （SCS） is estimated by using 24 CMIP5 models under different representative concentration pathway （RCP） scenarios. By the end of the 21st century （2081–2100 relative to 1986–2005）, the multimodel ensemble mean dynamic sea level （DSL） is projected to rise 0.9, 1.6, and 1.1 cm under RCP2.6, RCP4.5, and RCP8.5 scenarios, respectively, resulting in a total sea level rise （SLR） of 40.9, 48.6, and 64.1 cm in the SCS. It indicates that the SCS will experience a substantial SLR over the 21st century, and the rise is only marginal larger than the global mean SLR. During the same period, the steric sea level （SSL） rise is estimated to be 6.7, 10.0, and 15.3 cm under the three scenarios, respectively, which accounts only for 16%, 21% and 24% of the total SLR in this region. The changes of the SSL in the SCS are almost out of phase with those of the DSL for the three scenarios. The central deep basin has a slightly weak DSL rise, but a strong SSL rise during the 21st century, compared with the north and southwest shelves.展开更多
Theoretical and empirical studies have suggested that an underestimate of the ENSO asymmetry may be accompanied by a climatologically smaller and warmer western Pacific warm pool. In light of this suggestion, simulati...Theoretical and empirical studies have suggested that an underestimate of the ENSO asymmetry may be accompanied by a climatologically smaller and warmer western Pacific warm pool. In light of this suggestion, simulations of the tropical Pacific climate by 19 Coupled Model Intercomparison Project Phase 3 （CMIP3） climate models that do not use flux adjustment were evaluated. Our evaluation revealed systematic biases in both the mean state and ENSO statistics. The mean state in most of the models had a smaller and warmer warm pool. This common bias in the mean state was accompanied by a common bias in the simulated ENSO statistics： a significantly weak asymmetry between the two phases of ENSO. Moreover, despite the generally weak ENSO asymmetry simulated by all models, a positive correlation between the magnitude of the bias in the simulated warm-pool size and the magnitude of the bias in the simulated ENSO asymmetry was found. These findings support the suggested link between ENSO asymmetry and the tropical mean state--the climatological size and temperature of the warm pool in particular. Together with previous studies, these findings light up a path to improve the simulation of the tropical Pacific mean state by climate models： enhancing the asymmetry of ENSO in the climate models.展开更多
The climate system models from Beijing Climate Center, BCC_CSM1.1 and BCC_CSM1.1-M, are used to carry out most of the CMIP5 experiments. This study gives a general introduction of these two models, and provides main i...The climate system models from Beijing Climate Center, BCC_CSM1.1 and BCC_CSM1.1-M, are used to carry out most of the CMIP5 experiments. This study gives a general introduction of these two models, and provides main information on the experiments including the experiment purpose, design, and the external forcings. The transient climate responses to the CO2 concentration increase at 1% per year are presented in the simulation of the two models. The BCC_CSM1.1-M result is closer to the CMIP5 multiple models ensemble. The two models perform well in simulating the historical evolution of the surface air temperature, globally and averaged for China. Both models overestimate the global warming and underestimate the warming over China in the 20th century. With higher horizontal resolution, the BCC_CSM1.1-M has a better capability in reproducing the annual evolution of surface air temperature over China.展开更多
The diurnal temperature range(DTR)serves as a vital indicator reflecting both natural climate variability and anthropogenic climate change.This study investigates the historical and projected multitemporal DTR variati...The diurnal temperature range(DTR)serves as a vital indicator reflecting both natural climate variability and anthropogenic climate change.This study investigates the historical and projected multitemporal DTR variations over the Tibetan Plateau.It assesses 23 climate models from phase 6 of the Coupled Model Intercomparison Project(CMIP6)using CN05.1 observational data as validation,evaluating their ability to simulate DTR over the Tibetan Plateau.Then,the evolution of DTR over the Tibetan Plateau under different shared socioeconomic pathway(SSP)scenarios for the near,middle,and long term of future projection are analyzed using 11 selected robustly performing models.Key findings reveal:(1)Among the models examined,BCC-CSM2-MR,EC-Earth3,EC-Earth3-CC,EC-Earth3-Veg,EC-Earth3-Veg-LR,FGOALS-g3,FIO-ESM-2-0,GFDL-ESM4,MPI-ESM1-2-HR,MPI-ESM1-2-LR,and INM-CM5-0 exhibit superior integrated simulation capability for capturing the spatiotemporal variability of DTR over the Tibetan Plateau.(2)Projection indicates a slightly increasing trend in DTR on the Tibetan Plateau in the SSP1-2.6 scenario,and decreasing trends in the SSP2-4.5,SSP3-7.0,and SPP5-8.5 scenarios.In certain areas,such as the southeastern edge of the Tibetan Plateau,western hinterland of the Tibetan Plateau,southern Kunlun,and the Qaidam basins,the changes in DTR are relatively large.(3)Notably,the warming rate of maximum temperature under SSP2-4.5,SSP3-7.0,and SPP5-8.5 is slower compared to that of minimum temperature,and it emerges as the primary contributor to the projected decrease in DTR over the Tibetan Plateau in the future.展开更多
The present study evaluates the precipitation variability over the South China Sea（SCS） and its relationship to tropical Indo-Pacific SST anomalies during spring-to-summer transition（April–May–June,AMJ） simulate...The present study evaluates the precipitation variability over the South China Sea（SCS） and its relationship to tropical Indo-Pacific SST anomalies during spring-to-summer transition（April–May–June,AMJ） simulated by 23 Intergovernmental Panel on Climate Change Coupled Model Intercomparison Project Phase 5 coupled models.Most of the models have the capacity to capture the AMJ precipitation variability in the SCS.The precipitation and SST anomaly（SSTA） distribution in the SCS,tropical Pacific Ocean（TPO）,and tropical Indian Ocean（TIO） domains is evaluated based on the pattern correlation coefficients between model simulations and observations.The analysis leads to several points of note.First,the performance of the SCS precipitation anomaly pattern in AMJ is model dependent.Second,the SSTA pattern in the TPO and TIO is important for capturing the AMJ SCS precipitation variability.Third,a realistic simulation of the western equatorial Pacific（WEP） and local SST impacts is necessary for reproducing the AMJ SCS precipitation variability in some models.Fourth,the overly strong WEP SST impacts may disrupt the relationship between the SCS precipitation and the TPO–TIO SST.Further work remains to be conducted to unravel the specific reasons for the discrepancies between models and observations in various aspects.展开更多
To assess the performances of state-of-the-art global climate models on simulating the Arctic clouds and surface radiation balance,the 2001–2014 Arctic Basin surface radiation budget,clouds,and the cloud radiative ef...To assess the performances of state-of-the-art global climate models on simulating the Arctic clouds and surface radiation balance,the 2001–2014 Arctic Basin surface radiation budget,clouds,and the cloud radiative effects(CREs)in 22 coupled model intercomparison project 6(CMIP6)models are evaluated against satellite observations.For the results from CMIP6 multi-model mean,cloud fraction(CF)peaks in autumn and is lowest in winter and spring,consistent with that from three satellite observation products(Cloud Sat-CALIPSO,CERESMODIS,and APP-x).Simulated CF also shows consistent spatial patterns with those in observations.However,almost all models overestimate the CF amount throughout the year when compared to CERES-MODIS and APP-x.On average,clouds warm the surface of the Arctic Basin mainly via the longwave(LW)radiation cloud warming effect in winter.Simulated surface energy loss of LW is less than that in CERES-EBAF observation,while the net surface shortwave(SW)flux is underestimated.The biases may result from the stronger cloud LW warming effect and SW cooling effect from the overestimated CF by the models.These two biases compensate each other,yielding similar net surface radiation flux between model output(3.0 W/m2)and CERES-EBAF observation(6.1 W/m2).During 2001–2014,significant increasing trend of spring CF is found in the multi-model mean,consistent with previous studies based on surface and satellite observations.Although most of the 22 CMIP6 models show common seasonal cycles of CF and liquid water path/ice water path(LWP/IWP),large inter-model spreads exist in the amounts of CF and LWP/IWP throughout the year,indicating the influences of different cloud parameterization schemes used in different models.Cloud Feedback Model Intercomparison Project(CFMIP)observation simulator package(COSP)is a great tool to accurately assess the performance of climate models on simulating clouds.More intuitive and credible evaluation results can be obtained based on the COSP model output.In the future,with the release of more COSP output of CMIP6 models,it is expected that those inter-model spreads and the model-observation biases can be substantially reduced.Longer term active satellite observations are also necessary to evaluate models’cloud simulations and to further explore the role of clouds in the rapid Arctic climate changes.展开更多
Using 26 climate models from the Coupled Model Intercomparison Project Phase 5(CMIP5), climatology and the interannual variability of the annual mean Hadley circulation are evaluated. The results show that most of 26 ...Using 26 climate models from the Coupled Model Intercomparison Project Phase 5(CMIP5), climatology and the interannual variability of the annual mean Hadley circulation are evaluated. The results show that most of 26 models perform well in simulating the spatial structure of the climatology of the annual mean Hadley circulation, but the results derived from these models are generally weaker than that derived from the reanalysis dataset. Eighteen models can properly simulate well the asymmetric mode and symmetric mode of the annual mean Hadley circulation variability. Two models can only simulate asymmetric mode or symmetric mode and the other two models simulate reversed sequences of asymmetric mode and symmetric mode.The possible reason why some models cannot properly simulate the asymmetric mode and symmetric mode is that these models do not properly simulate the structure of zonal mean sea surface temperature(SST). Especially, not properly simulating variances of symmetric and asymmetric components of the SSTA will lead to reversed sequence of symmetric mode and asymmetric mode. And not properly simulated either symmetric or asymmetric component of the SSTA will lead to inability in simulating symmetric mode or asymmetric mode. On the other hand, some models properly simulate the asymmetric mode and symmetric mode, but do not properly simulate the responses to SST change.These models can not reflect the air sea coupling processes in associated with the Hadley circulation, therefore they should be taken more care when classify the models into groups.展开更多
The increases of atmospheric carbon dioxide and other greenhouse gases have caused fundamental changes to the physical and biogeochemical properties of the oceans,and it will continue to occur in the foreseeable futur...The increases of atmospheric carbon dioxide and other greenhouse gases have caused fundamental changes to the physical and biogeochemical properties of the oceans,and it will continue to occur in the foreseeable future.Based on the outputs of nine Earth System Models from the fifth phase of the Coupled Model Intercomparison Project(CMIP5),in this study,we provided a synoptic assessment of future changes in the sea surface temperature(SST),salinity,dissolved oxygen(DO),seawater pH,and marine net primary productivity(NPP)in the coastal China seas over the 21st century.The results show that the mid-high latitude areas of the coastal China seas(East China Seas(ECS),including the Bohai Sea,Yellow Sea,and East China Sea)will be simultaneously exposed to enhanced warming,deoxygenation,acidification,and decreasing NPP as a consequence of increasing greenhouse gas emissions.The magnitudes of the changes will increase as the greenhouse gas concentrations increase.Under the high emission scenario(Representative Concentration Pathway 8.5),the ECS will experience an SST increase of 3.24±1.23℃,a DO concentration decrease of 10.90±3.92μmol/L(decrease of 6.3%),a pH decline of 0.36±0.02,and a NPP reduction of-17.7±6.2 mg/(m2·d)(decrease of 12.9%)relative to the current levels(1980-2005)by the end of this century.The co-occurrence of these changes and their cascade effects are expected to induce considerable biological and ecological responses,thereby making the ECS among the most vulnerable ocean areas to future climate change.Despite high uncertainties,our results have important implications for regional marine assessments.展开更多
The South Pacific Quadrupole(SPQ) is the extratropical South Pacific’s second principal sea surface temperature mode.Previous observational studies have shown that the SPQ promotes the onset of the El Nino-Southern O...The South Pacific Quadrupole(SPQ) is the extratropical South Pacific’s second principal sea surface temperature mode.Previous observational studies have shown that the SPQ promotes the onset of the El Nino-Southern Oscillation(ENSO).The present study evaluates and compares simulations of the SPQ-ENSO relationship by 20 climate models from CMIP6 and their corresponding 20 previous models from CMIP5.It is found that 16 of the20 pairs of models are able to consistently reproduce the spatial pattern of the SPQ.In terms of simulating the SPQ-ENSO relationship,9 of the 16 CMIP6 models show significant improvement over their previous CMIP5 models.The multi-model ensemble(MME) of these 16 CMIP6 models simulates the SPQ-ENSO connection more realistically than the CMIP5 MME.Further analysis shows that the performance of the model simulations in reproducing the SPQ-ENSO relationship is strongly dependent on their ability to simulate the SPQ-related surface air-sea coupling processes over the southwestern and southeastern South Pacific,as well as the response of the SPQ-related equatorial subsurface ocean temperature anomalies.The improvement of the CMIP6 models in simulating these two processes is responsible for the improved performance of the CMIP6 models over their CMIP5 counterparts in simulating the SPQ-ENSO relationship.展开更多
The ocean could profoundly modulate the ever-increasing atmospheric CO_(2) by air-sea CO_(2) exchange process,which is also able to cause signifi cant changes of physical and biogeochemical properties in return.In thi...The ocean could profoundly modulate the ever-increasing atmospheric CO_(2) by air-sea CO_(2) exchange process,which is also able to cause signifi cant changes of physical and biogeochemical properties in return.In this study,we assessed the long-term average and spatial-temporal variability of global air-sea CO_(2) exchange fl ux(F CO_(2))since 1980s basing on the results of 18 Coupled Model Intercomparison Project Phase 6(CMIP6)Earth System Models(ESMs).Our fi ndings indicate that the CMIP6 ESMs simulated global CO_(2) sink in recent three decades ranges from 1.80 to 2.24 Pg C/a,which is coincidence with the results of cotemporaneous observations.What’s more,the CMIP6 ESMs consistently show that the global oceanic CO_(2) sink has gradually intensifi ed since 1980s as well as the observations.This study confi rms the simulated F CO_(2) could reach agreements with the observations in the aspect of primary climatological characteristics,however,the simulation skills of CIMP6 ESMs in diverse open-sea biomes are unevenness.None of the 18 CMIP6 ESMs could reproduce the observed F CO_(2) increasement in the central-eastern tropical Pacifi c and the midlatitude Southern Ocean.Defi ciencies of some CMIP6 ESMs in reproducing the atmospheric pressure systems of the Southern Hemisphere and the El Niño-Southern Oscillation(ENSO)mode of the tropical Pacifi c are probably the major causes.展开更多
Eleven climate system models that participate in the Coupled Model Intercomparison Project phase 5(CMIP5)were evaluated based on an assessment of their simulated meridional transports in comparison with the Sverdrup t...Eleven climate system models that participate in the Coupled Model Intercomparison Project phase 5(CMIP5)were evaluated based on an assessment of their simulated meridional transports in comparison with the Sverdrup transports.The analyses show that the simulated North Pacifi c Ocean circulation is essentially in Sverdrup balance in most of the 11 models while the Argo geostrophic meridional transports indicate signifi cant non-Sverdrup gyre circulation in the tropical North Pacifi c Ocean.The climate models overestimated the observed tropical and subtropical volume transports signifi cantly.The non-Sverdrup gyre circulation leads to non-Sverdrup heat and salt transports,the absence of which in the CMIP5 simulations suggests defi ciencies of the CMIP5 model dynamics in simulating the realistic meridional volume,heat,and salt transports of the ocean.展开更多
The climatologies of dissolved oxygen concentration in the ocean simulated by nine Earth system models(ESMs) from the historical emission driven experiment of CMIP5(Phase 5 of the Climate Model Intercomparison Project...The climatologies of dissolved oxygen concentration in the ocean simulated by nine Earth system models(ESMs) from the historical emission driven experiment of CMIP5(Phase 5 of the Climate Model Intercomparison Project) are quantitatively evaluated by comparing the simulated oxygen to the WOA09 observation based on common statistical metrics. At the sea surface, distribution of dissolved oxygen is well simulated by all nine ESMs due to well-simulated sea surface temperature(SST), with both globally-averaged error and root mean square error(RMSE) close to zero, and both correlation coefficients and normalized standard deviation close to 1. However, the model performance differs from each other at the intermediate depth and deep ocean where important water masses exist. At the depth of 500 to 1 000 m where the oxygen minimum zones(OMZs) exist, all ESMs show a maximum of globally-averaged error and RMSE, and a minimum of the spatial correlation coefficient. In the ocean interior, the reason for model biases is complicated, and both the meridional overturning circulation(MOC) and the particulate organic carbon flux contribute to the biases of dissolved oxygen distribution. Analysis results show the physical bias contributes more. Simulation bias of important water masses such as North Atlantic Deep Water(NADW), Antarctic Bottom Water(AABW) and North Pacific Intermediate Water(NPIW) indicated by distributions of MOCs greatly affects the distributions of oxygen in north Atlantic, Southern Ocean and north Pacific, respectively.Although the model simulations of oxygen differ greatly from each other in the ocean interior, the multi-model mean shows a better agreement with the observation.展开更多
The Paris Agreement aims to limit global warming to well below 2.00℃and pursue efforts to limit the temperature increase to 1.50℃.However,the response of climate change to unbalanced global warming is affected by sp...The Paris Agreement aims to limit global warming to well below 2.00℃and pursue efforts to limit the temperature increase to 1.50℃.However,the response of climate change to unbalanced global warming is affected by spatial and temporal sensitivities.To better understand the regional warming response to global warming at 1.50℃and 2.00℃,we detected the 1.50℃and 2.00℃warming threshold-crossing time(WTT)above pre-industrial levels globally using the Coupled Model Intercomparison Project phase 6(CMIP6)models.Our findings indicate that the 1.50℃or 2.00℃WTT differs substantially worldwide.The warming rate of land would be approximately 1.35–1.46 times that of the ocean between 60°N–60°S in 2015–2100.Consequently,the land would experience a 1.50℃(2.00℃)warming at least 10–20 yr earlier than the time when the global mean near-surface air temperature reaches 1.50℃(2.00℃)WTT.Meanwhile,the Southern Ocean between 0°and 60°S considerably slows down the global 1.50℃and 2.00℃WTT.In 2040–2060,over 98.70%(77.50%),99.70%(89.30%),99.80%(93.40%),and 100.00%(98.00%)of the land will have warmed by over 1.50℃(2.00℃)under SSP(Shared Socioeconomic Pathway)1–2.6,SSP2-4.5,SSP3-7.0,and SSP5-8.5,respectively.We conclude that regional 1.50℃(2.00℃)WTT should be fully considered,especially in vulnerable high-latitude and high-altitude regions.展开更多
The subtropical North and South Pacific Meridional Modes(NPMM and SPMM)are well known precursors of El Niño-Southern Oscillation(ENSO).However,relationship between them is not constant.In the early 1980,the relat...The subtropical North and South Pacific Meridional Modes(NPMM and SPMM)are well known precursors of El Niño-Southern Oscillation(ENSO).However,relationship between them is not constant.In the early 1980,the relationship experienced an interdecadal transition.Changes in this connection can be attributed mainly to the phase change of the Pacific decadal oscillation(PDO).During the positive phase of PDO,a shallower thermocline in the central Pacific is responsible for the stronger trade wind charging(TWC)mechanism,which leads to a stronger equatorial subsurface temperature evolution.This dynamic process strengthens the connection between NPMM and ENSO.Associated with the negative phase of PDO,a shallower thermocline over southeastern Pacific allows an enhanced wind-evaporation-SST(WES)feedback,strengthening the connection between SPMM and ENSO.Using 35 Coupled Model Intercomparison Project Phase 6(CMIP6)models,we examined the NPMM/SPMM performance and its connection with ENSO in the historical runs.The great majority of CMIP6 models can reproduce the pattern of NPMM and SPMM well,but they reveal discrepant ENSO and NPMM/SPMM relationship.The intermodal uncertainty for the connection of NPMM-ENSO is due to different TWC mechanism.A stronger TWC mechanism will enhance NPMM forcing.For SPMM,few models can simulate a good relationship with ENSO.The intermodel spread in the relationship of SPMM and ENSO owing to SST bias in the southeastern Pacific,as WES feedback is stronger when the southeastern Pacific is warmer.展开更多
The Pacific subtropical cells(STCs)are shallow meridional overturning circulations connecting the tropics and subtropics,and are assumed to be an important driver of the tropical Pacific decadal variability.The variab...The Pacific subtropical cells(STCs)are shallow meridional overturning circulations connecting the tropics and subtropics,and are assumed to be an important driver of the tropical Pacific decadal variability.The variability of STCs under global warming is investigated using multimodal outputs from the latest phase of the Coupled Model Inter-comparison Project(CMIP6)and ocean reanalysis products.Firstly,the volume transport diagnostic analysis is employed to evaluate how coupled models and ocean reanalysis products reproduce interior STC transport.The variation of heat transport by the interior STC under the high-emissions warming scenarios is also analyzed.The results show that the multimodal-mean linear trends of the interior STC transport along 9°S and 9°N are-0.02 Sv/a and 0.04 Sv/a under global warming,respectively,which is mainly due to the combined effect of the strengthened upper oceanic stratification and the weakening of wind field.There is a compensation relationship between the interior STC and the western boundary transport in the future climate,and the compensation relationship of 9°S is more significant than that of 9°N.In addition,compared with ocean reanalysis products,the coupled models tend to underestimate the variability of the interior STC transport convergence,and thus may lose some sea surface temperature(SST)driving force,which may be the reason for the low STC-SST correlation simulated by the model.The future scenario simulation shows that the heat transport of interior STC is weakened under global warming,with a general agreement across models.展开更多
本文基于观测和再分析资料,采用Brubaker二元模型评估了第六次国际耦合模式比较计划(CMIP6)中19个模式对中国东部季风区气候态水循环过程的模拟能力,并分析了模拟误差来源。结果表明,CMIP6模式集合平均(MME)能够合理再现观测降水和蒸发...本文基于观测和再分析资料,采用Brubaker二元模型评估了第六次国际耦合模式比较计划(CMIP6)中19个模式对中国东部季风区气候态水循环过程的模拟能力,并分析了模拟误差来源。结果表明,CMIP6模式集合平均(MME)能够合理再现观测降水和蒸发的年平均气候态空间分布及年循环特征,与观测值的空间相关系数分别为0.92和0.87。较之观测,MME高估了华北地区降水(0.55 mm d^(−1)),低估了华南沿海地区降水(−0.3 mm d^(−1))。所有CMIP6模式均高估蒸发强度(偏差0.03~0.98 mm d^(−1)),使得模拟的降水与蒸发之差偏少。模式整体能够模拟出我国东部季风区降水再循环率及不同边界水汽来源的贡献率,但低估了由南边界进入季风区的水汽贡献,导致东亚季风区偏干。通过分析模式对影响水汽通量的两个气象要素(风速和大气比湿)的模拟能力,发现研究区南边界的风速大小决定了模式间水汽输送差异。南边界风速越大的模式,由南边界进入的水汽通量越大,模式模拟的降水越多。西北太平洋辐合带的东西位置是影响南边界南风速的重要系统之一,辐合带位置偏东的模式模拟的南风强度较弱,使得水汽输送偏弱、降水偏少;反之,南边界水汽输送偏强、降水偏多。本文通过评估最新一代CMIP6模式在东亚水循环方面的模拟性能,指出了当前气候模式在模拟西太平洋辐合带位置方面存在的偏差及其对东亚水循环的影响。展开更多
基金Guangdong Major Project of Basic and Applied Basic Research(2020B0301030004)National Natural Science Foundation of China(72293604,42275026)Open Grants of the State Key Laboratory of Severe Weather(2023LASW-B09)。
文摘Pronounced climatic differences occur over subtropical South China(SC)and tropical South China Sea(SCS)and understanding the key cloud-radiation characteristics is essential to simulating East Asian climate.This study investigated cloud fractions and cloud radiative effects(CREs)over SC and SCS simulated by CMIP6 atmospheric models.Remarkable differences in cloud-radiation characteristics appeared over these two regions.In observations,considerable amounts of low-middle level clouds and cloud radiative cooling effect appeared over SC.In contrast,high clouds prevailed over SCS,where longwave and shortwave CREs offset each other,resulting in a weaker net cloud radiative effect(NCRE).The models underestimated NCRE over SC mainly due to weaker shortwave CRE and less cloud fractions.Conversely,most models overestimated NCRE over SCS because of stronger shortwave CRE and weaker longwave CRE.Regional CREs were closely linked to their dominant cloud fractions.Both observations and simulations showed a negative spatial correlation between total(low)cloud fraction and shortwave CRE over SC,especially in winter,and exhibited a positive correlation between high cloud fraction and longwave CRE over these two regions.Compared with SCS,most models overestimated the spatial correlation between low(high)cloud fraction and SWCRE(LWCRE)over SC,with larger bias ranges among models,indicating the exaggerated cloud radiative cooling(warming)effect caused by low(high)clouds.Moreover,most models struggled to describe regional ascent and its connection with CREs over SC while they can better reproduce these connections over SCS.This study further suggests that reasonable circulation conditions are crucial to simulating well cloud-radiation characteristics over the East Asian regions.
基金supported by a key project of the National Natural Science Foundation of China[grant number 42192563]。
文摘Against the backdrop of climate change,the activity of tropical cyclones(TCs)has captured widespread attention.Observational datasets indicate a declining trend in the genesis longitude of western North Pacific(WNP)TCs.This study investigates the zonal changes of WNP TCs with CMIP6-HighResMIP models.These models capture the genesis density of WNP TCs fairly well.The results reveal a westward shift in TC genesis longitude.This trend is associated with the significant reduction in the TC frequency over the southeastern WNP.The study also discusses changes in large-scale circulation patterns and the impact of the strengthening Pacific Walker circulation.
基金supported by the Key Research and Development Project of Xinjiang Uygur Autonomous Region,China(2022B02049)the Major Science and Technology Special Project of Xinjiang Uygur Autonomous Region,China(2024A03007-5).
文摘In the northern Tarim River Basin,the Weigan River Basin is a critical endorheic system characterized by extreme aridity,where drought poses a major natural hazard to agricultural production and ecological stability.This study assessed the future evolution of drought under climate change by employing the standardized moisture anomaly index(SZI)on the basis of multi-model the Coupled Model Intercomparison Project Phase 6(CMIP6)simulations under historical conditions(1970–2014)and future scenarios(shared socioeconomic pathway(SSP)1-2.6,SSP2-4.5,SSP3-7.0 and SSP5-8.5 for 2015–2100).The results show that precipitation–evapotranspiration anomalies are projected to first decline but then increase over time,with increased fluctuations and uncertainty under high-emission scenarios(SSP5-8.5).These trends indicate intensifying drought risks and reveal a strong influence of emission pathways on regional water cycling.Temporal analysis of SZI indicates a transition from wetting to drying under lowand medium-emission pathways(SSP1-2.6 and SSP2-4.5),whereas high-emission scenarios are characterized by persistent drying and increased variability.The significant lower-tail dependence(0.271)observed under SSP2-4.5 and SSP5-8.5 suggests that extreme droughts may be subject to nonlinear co-amplification across scenarios.The frequency of moderate and more severe drought events is expected to increase substantially,especially under SSP5-8.5,where drought occurrence is predicted to extend into spring and autumn and become more evenly distributed throughout the year.Spatially,drought duration shows significant positive autocorrelation across all scenarios,with hot spots consistently concentrated in the southern and southeastern regions of the basin.Random forest analysis,interpreted as association-based pattern attribution,indicates that meteorological variables(precipitation and potential evapotranspiration(PET))make the greatest contributions to the hot spot pattern,followed by topography and soil moisture.Among land use categories,farmland generally shows higher drought sensitivity than other land use types,as reflected by its relative contribution patterns across scenarios.The spatial pattern of drought is statistically structured by climatic forcing,surface conditions,and soil moisture status,reflecting their coupled associations with hot spot occurrence.In addition,a drought spatial uncertainty index was constructed from multi-scenario hot spot maps,revealing spatially heterogeneous structural variability throughout the basin.Correlation analysis further highlights strong internal couplings among environmental variables(e.g.,elevation-linked hydroclimatic gradients and grassland–bare soil contrasts).These findings offer a scientific basis for developing region-specific drought monitoring and adaptation strategies under future climate change conditions.
基金supported by the National Key Basic Research Program of China(Grant No.2009CB421404)the National Natural Science Foundation of China(Grant No.41175076)+2 种基金the Fundamental Research Funds for the Central Universities(Grant No.11lgjc10)the support of a Direct Grant of the Chinese University of Hong Kong(Grant No.2021105)a Hong Kong Research Grants Council Project(CUHK No.403612)
文摘Precipitation and surface temperature are two important quantities whose variations are closely related through various physical processes. In the present study, we evaluated the precipitation-surface temperature （P-T） relationship in 17 climate models involved in the Coupled Model Intercomparison Project Phase 5 （CMIP5） for the IPCC Assessment Report version 5. Most models performed reasonably well at simulat- ing the large-scale features of the P-T correlation distribution. Based on the pattern correlation of the P-T correlation distribution, the models performed better in November-December-January-February-March （NDJFM） than in May-June-July-August-September （MJJAS） except for the mid-latitudes of the North- ern Hemisphere, and the performance was generally better over the land than over the ocean. Seasonal dependence was more obvious over the land than over the ocean and was more obvious over the mid- and high-latitudes than over the tropics. All of the models appear to have had difficulty capturing the P-T correlation distribution over the mid-latitudes of the Southern Hemisphere in MJJAS. The spatial variabil- ity of the P-T correlation in the models was overestimated compared to observations. This overestimation tended to be larger over the land than over the ocean and larger over the mid- and high-latitudes than over the tropics. Based on analyses of selected model ensemble simulations, the spread of the P-T correlation among the ensemble members appears to have been small. While the performance in the P-T correlation provides a general direction for future improvement of climate models, the specific reasons for the discrep- ancies between models and observations remain to be revealed with detailed and comprehensive evaluations in various aspects.
基金The National Basic Research Program(973 Program)of China under contract No.2010CB950501the National Natural Science Foundation of China under contract No.41276035the National Natural Science Foundation of China–Shandong Province Joint Fund of Marine Science Research Centers under contract No.U1406404
文摘Future potential sea level change in the South China Sea （SCS） is estimated by using 24 CMIP5 models under different representative concentration pathway （RCP） scenarios. By the end of the 21st century （2081–2100 relative to 1986–2005）, the multimodel ensemble mean dynamic sea level （DSL） is projected to rise 0.9, 1.6, and 1.1 cm under RCP2.6, RCP4.5, and RCP8.5 scenarios, respectively, resulting in a total sea level rise （SLR） of 40.9, 48.6, and 64.1 cm in the SCS. It indicates that the SCS will experience a substantial SLR over the 21st century, and the rise is only marginal larger than the global mean SLR. During the same period, the steric sea level （SSL） rise is estimated to be 6.7, 10.0, and 15.3 cm under the three scenarios, respectively, which accounts only for 16%, 21% and 24% of the total SLR in this region. The changes of the SSL in the SCS are almost out of phase with those of the DSL for the three scenarios. The central deep basin has a slightly weak DSL rise, but a strong SSL rise during the 21st century, compared with the north and southwest shelves.
基金supported by the Strategic Priority Research Program-Climate Change:Carbon Budget and Related Issues of the Chinese Academy of Sciences(Grant No.XDA05110302)National Natural Science Foundation of China(NSFC)Major Research Project(Grant Nos.40890150 and 40890155)+2 种基金the National Basic Research Program of China for Structures,Variability,and Climatic Impacts of Ocean Circulation and Warm Pool in the Tropical Pacific Ocean(Grant No.2012CB417401)China Postdoctoral Science Foudation funded project(2012M521378)Chinese Scholarship Council,the Large-scale and Climate Dynamics Program of the US National Science Foundation(Grant Nos.AGS0553111 and AGS0852329)
文摘Theoretical and empirical studies have suggested that an underestimate of the ENSO asymmetry may be accompanied by a climatologically smaller and warmer western Pacific warm pool. In light of this suggestion, simulations of the tropical Pacific climate by 19 Coupled Model Intercomparison Project Phase 3 （CMIP3） climate models that do not use flux adjustment were evaluated. Our evaluation revealed systematic biases in both the mean state and ENSO statistics. The mean state in most of the models had a smaller and warmer warm pool. This common bias in the mean state was accompanied by a common bias in the simulated ENSO statistics： a significantly weak asymmetry between the two phases of ENSO. Moreover, despite the generally weak ENSO asymmetry simulated by all models, a positive correlation between the magnitude of the bias in the simulated warm-pool size and the magnitude of the bias in the simulated ENSO asymmetry was found. These findings support the suggested link between ENSO asymmetry and the tropical mean state--the climatological size and temperature of the warm pool in particular. Together with previous studies, these findings light up a path to improve the simulation of the tropical Pacific mean state by climate models： enhancing the asymmetry of ENSO in the climate models.
基金supported by the National Basic Research Program of China (973 Program) under No. 2010CB951903the National Science Foundation of China under Grant No. 41105054, 41205043the China Meteorological Administration under Grant No.GYHY201106022, GYHY201306048, CMAYBY2012-001
文摘The climate system models from Beijing Climate Center, BCC_CSM1.1 and BCC_CSM1.1-M, are used to carry out most of the CMIP5 experiments. This study gives a general introduction of these two models, and provides main information on the experiments including the experiment purpose, design, and the external forcings. The transient climate responses to the CO2 concentration increase at 1% per year are presented in the simulation of the two models. The BCC_CSM1.1-M result is closer to the CMIP5 multiple models ensemble. The two models perform well in simulating the historical evolution of the surface air temperature, globally and averaged for China. Both models overestimate the global warming and underestimate the warming over China in the 20th century. With higher horizontal resolution, the BCC_CSM1.1-M has a better capability in reproducing the annual evolution of surface air temperature over China.
基金supported by The Second Tibetan Plateau Scientific Expedition and Research(STEP)program(Grant No.2019QZKK0102)the National Natural Science Foundation of China(Grant No.41975135)+1 种基金the Natural Science Foundation of Sichuan,China(Grant No.2022NSFSC1092)funded by the China Scholarship Council。
文摘The diurnal temperature range(DTR)serves as a vital indicator reflecting both natural climate variability and anthropogenic climate change.This study investigates the historical and projected multitemporal DTR variations over the Tibetan Plateau.It assesses 23 climate models from phase 6 of the Coupled Model Intercomparison Project(CMIP6)using CN05.1 observational data as validation,evaluating their ability to simulate DTR over the Tibetan Plateau.Then,the evolution of DTR over the Tibetan Plateau under different shared socioeconomic pathway(SSP)scenarios for the near,middle,and long term of future projection are analyzed using 11 selected robustly performing models.Key findings reveal:(1)Among the models examined,BCC-CSM2-MR,EC-Earth3,EC-Earth3-CC,EC-Earth3-Veg,EC-Earth3-Veg-LR,FGOALS-g3,FIO-ESM-2-0,GFDL-ESM4,MPI-ESM1-2-HR,MPI-ESM1-2-LR,and INM-CM5-0 exhibit superior integrated simulation capability for capturing the spatiotemporal variability of DTR over the Tibetan Plateau.(2)Projection indicates a slightly increasing trend in DTR on the Tibetan Plateau in the SSP1-2.6 scenario,and decreasing trends in the SSP2-4.5,SSP3-7.0,and SPP5-8.5 scenarios.In certain areas,such as the southeastern edge of the Tibetan Plateau,western hinterland of the Tibetan Plateau,southern Kunlun,and the Qaidam basins,the changes in DTR are relatively large.(3)Notably,the warming rate of maximum temperature under SSP2-4.5,SSP3-7.0,and SPP5-8.5 is slower compared to that of minimum temperature,and it emerges as the primary contributor to the projected decrease in DTR over the Tibetan Plateau in the future.
基金supported by the National Key Basic Research Program of China(Grant No.2014CB953902)the support of the Hong Kong Research Grants Council(Grant No.CUHK403612)+4 种基金the National Natural Science Foundation of China(Grants Nos.41275081 and 41475081)a Chinese University of Hong Kong direct grant(Grant No.4052057)the support of a Chinese Academy of Sciences project(Grant No.XDA11010402)the National Natural Science Foundation of China(Grant Nos.41305065 and 41305068)the support of the State Key Laboratory of Tropical Oceanography,South China Sea Institute of Oceanology of Chinese Academy of Sciences(Grant No.LTO1203)
文摘The present study evaluates the precipitation variability over the South China Sea（SCS） and its relationship to tropical Indo-Pacific SST anomalies during spring-to-summer transition（April–May–June,AMJ） simulated by 23 Intergovernmental Panel on Climate Change Coupled Model Intercomparison Project Phase 5 coupled models.Most of the models have the capacity to capture the AMJ precipitation variability in the SCS.The precipitation and SST anomaly（SSTA） distribution in the SCS,tropical Pacific Ocean（TPO）,and tropical Indian Ocean（TIO） domains is evaluated based on the pattern correlation coefficients between model simulations and observations.The analysis leads to several points of note.First,the performance of the SCS precipitation anomaly pattern in AMJ is model dependent.Second,the SSTA pattern in the TPO and TIO is important for capturing the AMJ SCS precipitation variability.Third,a realistic simulation of the western equatorial Pacific（WEP） and local SST impacts is necessary for reproducing the AMJ SCS precipitation variability in some models.Fourth,the overly strong WEP SST impacts may disrupt the relationship between the SCS precipitation and the TPO–TIO SST.Further work remains to be conducted to unravel the specific reasons for the discrepancies between models and observations in various aspects.
基金The Major State Basic Research Development Program of China under contract No.2016YFA0601804the Global Change Research Program of China under contract No.2015CB953900+1 种基金the National Natural Science Foundation of China under contract Nos 41941007 and 41876220the China Postdoctoral Science Foundation under contract No.2020M681661
文摘To assess the performances of state-of-the-art global climate models on simulating the Arctic clouds and surface radiation balance,the 2001–2014 Arctic Basin surface radiation budget,clouds,and the cloud radiative effects(CREs)in 22 coupled model intercomparison project 6(CMIP6)models are evaluated against satellite observations.For the results from CMIP6 multi-model mean,cloud fraction(CF)peaks in autumn and is lowest in winter and spring,consistent with that from three satellite observation products(Cloud Sat-CALIPSO,CERESMODIS,and APP-x).Simulated CF also shows consistent spatial patterns with those in observations.However,almost all models overestimate the CF amount throughout the year when compared to CERES-MODIS and APP-x.On average,clouds warm the surface of the Arctic Basin mainly via the longwave(LW)radiation cloud warming effect in winter.Simulated surface energy loss of LW is less than that in CERES-EBAF observation,while the net surface shortwave(SW)flux is underestimated.The biases may result from the stronger cloud LW warming effect and SW cooling effect from the overestimated CF by the models.These two biases compensate each other,yielding similar net surface radiation flux between model output(3.0 W/m2)and CERES-EBAF observation(6.1 W/m2).During 2001–2014,significant increasing trend of spring CF is found in the multi-model mean,consistent with previous studies based on surface and satellite observations.Although most of the 22 CMIP6 models show common seasonal cycles of CF and liquid water path/ice water path(LWP/IWP),large inter-model spreads exist in the amounts of CF and LWP/IWP throughout the year,indicating the influences of different cloud parameterization schemes used in different models.Cloud Feedback Model Intercomparison Project(CFMIP)observation simulator package(COSP)is a great tool to accurately assess the performance of climate models on simulating clouds.More intuitive and credible evaluation results can be obtained based on the COSP model output.In the future,with the release of more COSP output of CMIP6 models,it is expected that those inter-model spreads and the model-observation biases can be substantially reduced.Longer term active satellite observations are also necessary to evaluate models’cloud simulations and to further explore the role of clouds in the rapid Arctic climate changes.
基金supported by the National Natural Science Foundation of China (41530424 and 41475076)
文摘Using 26 climate models from the Coupled Model Intercomparison Project Phase 5(CMIP5), climatology and the interannual variability of the annual mean Hadley circulation are evaluated. The results show that most of 26 models perform well in simulating the spatial structure of the climatology of the annual mean Hadley circulation, but the results derived from these models are generally weaker than that derived from the reanalysis dataset. Eighteen models can properly simulate well the asymmetric mode and symmetric mode of the annual mean Hadley circulation variability. Two models can only simulate asymmetric mode or symmetric mode and the other two models simulate reversed sequences of asymmetric mode and symmetric mode.The possible reason why some models cannot properly simulate the asymmetric mode and symmetric mode is that these models do not properly simulate the structure of zonal mean sea surface temperature(SST). Especially, not properly simulating variances of symmetric and asymmetric components of the SSTA will lead to reversed sequence of symmetric mode and asymmetric mode. And not properly simulated either symmetric or asymmetric component of the SSTA will lead to inability in simulating symmetric mode or asymmetric mode. On the other hand, some models properly simulate the asymmetric mode and symmetric mode, but do not properly simulate the responses to SST change.These models can not reflect the air sea coupling processes in associated with the Hadley circulation, therefore they should be taken more care when classify the models into groups.
基金Supported by the National Key R&D Program of China(Nos.2017YFA0604901,2017YFA0604902)the Scientific Research Foundation of the Third Institute of Oceanography,Ministry of Natural Resources,China(No.TIO2017030)the Major Project of National Social Science Foundation(No.17ZDA172)。
文摘The increases of atmospheric carbon dioxide and other greenhouse gases have caused fundamental changes to the physical and biogeochemical properties of the oceans,and it will continue to occur in the foreseeable future.Based on the outputs of nine Earth System Models from the fifth phase of the Coupled Model Intercomparison Project(CMIP5),in this study,we provided a synoptic assessment of future changes in the sea surface temperature(SST),salinity,dissolved oxygen(DO),seawater pH,and marine net primary productivity(NPP)in the coastal China seas over the 21st century.The results show that the mid-high latitude areas of the coastal China seas(East China Seas(ECS),including the Bohai Sea,Yellow Sea,and East China Sea)will be simultaneously exposed to enhanced warming,deoxygenation,acidification,and decreasing NPP as a consequence of increasing greenhouse gas emissions.The magnitudes of the changes will increase as the greenhouse gas concentrations increase.Under the high emission scenario(Representative Concentration Pathway 8.5),the ECS will experience an SST increase of 3.24±1.23℃,a DO concentration decrease of 10.90±3.92μmol/L(decrease of 6.3%),a pH decline of 0.36±0.02,and a NPP reduction of-17.7±6.2 mg/(m2·d)(decrease of 12.9%)relative to the current levels(1980-2005)by the end of this century.The co-occurrence of these changes and their cascade effects are expected to induce considerable biological and ecological responses,thereby making the ECS among the most vulnerable ocean areas to future climate change.Despite high uncertainties,our results have important implications for regional marine assessments.
基金This research was jointly supported by the National Natural Science Foundation of China[Grant number 41975070]the State Key Laboratory of Tropical Oceanography,South China Sea Institute of Oceanology,Chinese Academy of Sciences[Project number LTO1901].
文摘The South Pacific Quadrupole(SPQ) is the extratropical South Pacific’s second principal sea surface temperature mode.Previous observational studies have shown that the SPQ promotes the onset of the El Nino-Southern Oscillation(ENSO).The present study evaluates and compares simulations of the SPQ-ENSO relationship by 20 climate models from CMIP6 and their corresponding 20 previous models from CMIP5.It is found that 16 of the20 pairs of models are able to consistently reproduce the spatial pattern of the SPQ.In terms of simulating the SPQ-ENSO relationship,9 of the 16 CMIP6 models show significant improvement over their previous CMIP5 models.The multi-model ensemble(MME) of these 16 CMIP6 models simulates the SPQ-ENSO connection more realistically than the CMIP5 MME.Further analysis shows that the performance of the model simulations in reproducing the SPQ-ENSO relationship is strongly dependent on their ability to simulate the SPQ-related surface air-sea coupling processes over the southwestern and southeastern South Pacific,as well as the response of the SPQ-related equatorial subsurface ocean temperature anomalies.The improvement of the CMIP6 models in simulating these two processes is responsible for the improved performance of the CMIP6 models over their CMIP5 counterparts in simulating the SPQ-ENSO relationship.
基金Supported by the National Natural Science Foundation of China(No.41806133)the Marine S&T Fund of Shandong Province for the Pilot National Laboratory for Marine Science and Technology(Qingdao)(No.2022QNLM040003-1)+1 种基金the National Key Research and Development Program of China(No.2017YFA0603204)the Fund of Key Laboratory of Global Change and Marine-Atmospheric Chemistry,MNR(No.GCMAC1905)。
文摘The ocean could profoundly modulate the ever-increasing atmospheric CO_(2) by air-sea CO_(2) exchange process,which is also able to cause signifi cant changes of physical and biogeochemical properties in return.In this study,we assessed the long-term average and spatial-temporal variability of global air-sea CO_(2) exchange fl ux(F CO_(2))since 1980s basing on the results of 18 Coupled Model Intercomparison Project Phase 6(CMIP6)Earth System Models(ESMs).Our fi ndings indicate that the CMIP6 ESMs simulated global CO_(2) sink in recent three decades ranges from 1.80 to 2.24 Pg C/a,which is coincidence with the results of cotemporaneous observations.What’s more,the CMIP6 ESMs consistently show that the global oceanic CO_(2) sink has gradually intensifi ed since 1980s as well as the observations.This study confi rms the simulated F CO_(2) could reach agreements with the observations in the aspect of primary climatological characteristics,however,the simulation skills of CIMP6 ESMs in diverse open-sea biomes are unevenness.None of the 18 CMIP6 ESMs could reproduce the observed F CO_(2) increasement in the central-eastern tropical Pacifi c and the midlatitude Southern Ocean.Defi ciencies of some CMIP6 ESMs in reproducing the atmospheric pressure systems of the Southern Hemisphere and the El Niño-Southern Oscillation(ENSO)mode of the tropical Pacifi c are probably the major causes.
基金Supported by the National Natural Foundation of China(Nos.41421005,41720104008,91858204)the National Basic Research Program of China(973 Program)(No.2012CB956001)+2 种基金the Qingdao National Laboratory for Marine Science and Technology(No.2016ASKJ04)the Chinese Academy of Science(No.XDA11010205)the Shandong Provincial Projects(Nos.2014GJJS0101,U1406401)。
文摘Eleven climate system models that participate in the Coupled Model Intercomparison Project phase 5(CMIP5)were evaluated based on an assessment of their simulated meridional transports in comparison with the Sverdrup transports.The analyses show that the simulated North Pacifi c Ocean circulation is essentially in Sverdrup balance in most of the 11 models while the Argo geostrophic meridional transports indicate signifi cant non-Sverdrup gyre circulation in the tropical North Pacifi c Ocean.The climate models overestimated the observed tropical and subtropical volume transports signifi cantly.The non-Sverdrup gyre circulation leads to non-Sverdrup heat and salt transports,the absence of which in the CMIP5 simulations suggests defi ciencies of the CMIP5 model dynamics in simulating the realistic meridional volume,heat,and salt transports of the ocean.
基金The National Natural Science Foundation of China under contract No.41306029the Basic Scientific Fund for National Public Research Institutes of China under contract Nos 2013T01 and 2014G25
文摘The climatologies of dissolved oxygen concentration in the ocean simulated by nine Earth system models(ESMs) from the historical emission driven experiment of CMIP5(Phase 5 of the Climate Model Intercomparison Project) are quantitatively evaluated by comparing the simulated oxygen to the WOA09 observation based on common statistical metrics. At the sea surface, distribution of dissolved oxygen is well simulated by all nine ESMs due to well-simulated sea surface temperature(SST), with both globally-averaged error and root mean square error(RMSE) close to zero, and both correlation coefficients and normalized standard deviation close to 1. However, the model performance differs from each other at the intermediate depth and deep ocean where important water masses exist. At the depth of 500 to 1 000 m where the oxygen minimum zones(OMZs) exist, all ESMs show a maximum of globally-averaged error and RMSE, and a minimum of the spatial correlation coefficient. In the ocean interior, the reason for model biases is complicated, and both the meridional overturning circulation(MOC) and the particulate organic carbon flux contribute to the biases of dissolved oxygen distribution. Analysis results show the physical bias contributes more. Simulation bias of important water masses such as North Atlantic Deep Water(NADW), Antarctic Bottom Water(AABW) and North Pacific Intermediate Water(NPIW) indicated by distributions of MOCs greatly affects the distributions of oxygen in north Atlantic, Southern Ocean and north Pacific, respectively.Although the model simulations of oxygen differ greatly from each other in the ocean interior, the multi-model mean shows a better agreement with the observation.
基金Under the auspices of the Second Tibetan Plateau Scientific Expedition and Research Program(STEP)(No.2019QZKK020104)the National Natural Science Foundation of China(No.41571062,42101122)+2 种基金the Fundamental Research Funds for the Central Universities(No.2020TS100)the Natural Science Foundation of Shaanxi Province,China(No.2023-JC-YB-259)the China Postdoctoral Science Foundation(No.2017M610622)。
文摘The Paris Agreement aims to limit global warming to well below 2.00℃and pursue efforts to limit the temperature increase to 1.50℃.However,the response of climate change to unbalanced global warming is affected by spatial and temporal sensitivities.To better understand the regional warming response to global warming at 1.50℃and 2.00℃,we detected the 1.50℃and 2.00℃warming threshold-crossing time(WTT)above pre-industrial levels globally using the Coupled Model Intercomparison Project phase 6(CMIP6)models.Our findings indicate that the 1.50℃or 2.00℃WTT differs substantially worldwide.The warming rate of land would be approximately 1.35–1.46 times that of the ocean between 60°N–60°S in 2015–2100.Consequently,the land would experience a 1.50℃(2.00℃)warming at least 10–20 yr earlier than the time when the global mean near-surface air temperature reaches 1.50℃(2.00℃)WTT.Meanwhile,the Southern Ocean between 0°and 60°S considerably slows down the global 1.50℃and 2.00℃WTT.In 2040–2060,over 98.70%(77.50%),99.70%(89.30%),99.80%(93.40%),and 100.00%(98.00%)of the land will have warmed by over 1.50℃(2.00℃)under SSP(Shared Socioeconomic Pathway)1–2.6,SSP2-4.5,SSP3-7.0,and SSP5-8.5,respectively.We conclude that regional 1.50℃(2.00℃)WTT should be fully considered,especially in vulnerable high-latitude and high-altitude regions.
基金Supported by the National Natural Science Foundation of China(NSFC)(No.41976027)。
文摘The subtropical North and South Pacific Meridional Modes(NPMM and SPMM)are well known precursors of El Niño-Southern Oscillation(ENSO).However,relationship between them is not constant.In the early 1980,the relationship experienced an interdecadal transition.Changes in this connection can be attributed mainly to the phase change of the Pacific decadal oscillation(PDO).During the positive phase of PDO,a shallower thermocline in the central Pacific is responsible for the stronger trade wind charging(TWC)mechanism,which leads to a stronger equatorial subsurface temperature evolution.This dynamic process strengthens the connection between NPMM and ENSO.Associated with the negative phase of PDO,a shallower thermocline over southeastern Pacific allows an enhanced wind-evaporation-SST(WES)feedback,strengthening the connection between SPMM and ENSO.Using 35 Coupled Model Intercomparison Project Phase 6(CMIP6)models,we examined the NPMM/SPMM performance and its connection with ENSO in the historical runs.The great majority of CMIP6 models can reproduce the pattern of NPMM and SPMM well,but they reveal discrepant ENSO and NPMM/SPMM relationship.The intermodal uncertainty for the connection of NPMM-ENSO is due to different TWC mechanism.A stronger TWC mechanism will enhance NPMM forcing.For SPMM,few models can simulate a good relationship with ENSO.The intermodel spread in the relationship of SPMM and ENSO owing to SST bias in the southeastern Pacific,as WES feedback is stronger when the southeastern Pacific is warmer.
基金the National Natural Science Foundation of China(NSFC)(No.41976027)。
文摘The Pacific subtropical cells(STCs)are shallow meridional overturning circulations connecting the tropics and subtropics,and are assumed to be an important driver of the tropical Pacific decadal variability.The variability of STCs under global warming is investigated using multimodal outputs from the latest phase of the Coupled Model Inter-comparison Project(CMIP6)and ocean reanalysis products.Firstly,the volume transport diagnostic analysis is employed to evaluate how coupled models and ocean reanalysis products reproduce interior STC transport.The variation of heat transport by the interior STC under the high-emissions warming scenarios is also analyzed.The results show that the multimodal-mean linear trends of the interior STC transport along 9°S and 9°N are-0.02 Sv/a and 0.04 Sv/a under global warming,respectively,which is mainly due to the combined effect of the strengthened upper oceanic stratification and the weakening of wind field.There is a compensation relationship between the interior STC and the western boundary transport in the future climate,and the compensation relationship of 9°S is more significant than that of 9°N.In addition,compared with ocean reanalysis products,the coupled models tend to underestimate the variability of the interior STC transport convergence,and thus may lose some sea surface temperature(SST)driving force,which may be the reason for the low STC-SST correlation simulated by the model.The future scenario simulation shows that the heat transport of interior STC is weakened under global warming,with a general agreement across models.
文摘本文基于观测和再分析资料,采用Brubaker二元模型评估了第六次国际耦合模式比较计划(CMIP6)中19个模式对中国东部季风区气候态水循环过程的模拟能力,并分析了模拟误差来源。结果表明,CMIP6模式集合平均(MME)能够合理再现观测降水和蒸发的年平均气候态空间分布及年循环特征,与观测值的空间相关系数分别为0.92和0.87。较之观测,MME高估了华北地区降水(0.55 mm d^(−1)),低估了华南沿海地区降水(−0.3 mm d^(−1))。所有CMIP6模式均高估蒸发强度(偏差0.03~0.98 mm d^(−1)),使得模拟的降水与蒸发之差偏少。模式整体能够模拟出我国东部季风区降水再循环率及不同边界水汽来源的贡献率,但低估了由南边界进入季风区的水汽贡献,导致东亚季风区偏干。通过分析模式对影响水汽通量的两个气象要素(风速和大气比湿)的模拟能力,发现研究区南边界的风速大小决定了模式间水汽输送差异。南边界风速越大的模式,由南边界进入的水汽通量越大,模式模拟的降水越多。西北太平洋辐合带的东西位置是影响南边界南风速的重要系统之一,辐合带位置偏东的模式模拟的南风强度较弱,使得水汽输送偏弱、降水偏少;反之,南边界水汽输送偏强、降水偏多。本文通过评估最新一代CMIP6模式在东亚水循环方面的模拟性能,指出了当前气候模式在模拟西太平洋辐合带位置方面存在的偏差及其对东亚水循环的影响。
