Based on reanalysis data and CMIP6 simulations,this study investigates the distinct responses of the cross-equatorial flows(CEFs)over the Maritime Continent(MC)under the simultaneous summer condition of two types of E...Based on reanalysis data and CMIP6 simulations,this study investigates the distinct responses of the cross-equatorial flows(CEFs)over the Maritime Continent(MC)under the simultaneous summer condition of two types of ENSO:central Pacific(CP)and eastern Pacific(EP).Results indicate that CP ENSO tends to exert stronger impacts on CEF.In CP ENSO years,significant lower-level southerly anomalies can be observed across all CEF branches adjacent to MC,accompanied by broader and deeper upper-level northerly anomalies,indicating a well-organized strengthening of both upper-and lowerlevel CEFs.In contrast,CEF anomalies in EP ENSO years tend to be weaker,with significant meridional wind anomalies confined to the east of MC.The disparities in the CEF responses can be elucidated from the perspective of convection over MC,a crucial factor in triggering CEF.In CP ENSO years,westward-leaning sea surface temperature(SST)anomalies result in a distinct cooling in MC and suppressed convection above,driving pronounced CEF anomalies.Conversely,the absence of such organized SST cooling during EP ENSO results in weaker convective forcing and subdued CEF responses.Furthermore,historical simulations from 48 CMIP6 models are utilized to validate the observational findings.Results show that model simulations can successfully reproduce the stronger impacts of CP ENSO,with a remarkable intermodel consistency.This research contributes toward a comprehensive understanding of the diversity in the relationship between CEF and ENSO types,and has implications for seasonal forecasting of CEF variability.展开更多
The predictability of a coupled system composed of a coupled reduced-order extratropical ocean-atmosphere model forced by a low-order three-variable tropical recharge-discharge model is explored with emphasis on its l...The predictability of a coupled system composed of a coupled reduced-order extratropical ocean-atmosphere model forced by a low-order three-variable tropical recharge-discharge model is explored with emphasis on its long-term forecasting capabilities.Highly idealized ensemble forecasts are produced taking into account the uncertainties in the initial states of the system,with specific attention to the structure of the initial errors in the tropical model.Three main types of experiments are explored:with random perturbations along the three Lyapunov vectors of the tropical model;along the two dominant Lyapunov vectors;and along the first Lyapunov vector only.When perturbations are introduced along all vectors,forecasting biases develop even if in a perfect model framework and with known initial uncertainty properties.Theses biases are considerably reduced only when the perturbations are introduced along the dominant Lyapunov vector.Furthermore,this perturbation strategy allows a reduced mean square error to be obtained at long lead times of a few years,as well as reliable ensemble forecasts across the whole time range.These very counterintuitive findings further underline the importance of appropriately controlling the initial error structure in the tropics through data assimilation.展开更多
Previous studies have shown that the Eocene oil shale sequences in the Green River Basin contain long-period astronomical age information.The fine-scale chronological characteristics of the oil shale laminae remain la...Previous studies have shown that the Eocene oil shale sequences in the Green River Basin contain long-period astronomical age information.The fine-scale chronological characteristics of the oil shale laminae remain largely unexplored.We selected finely laminated oil shales formed in deep-water environments characterized by stable water column stratification as the primary focus of this study,using microscopy and micro-area X-ray fluorescence(μ-XRF)techniques.By integrating high-resolution elemental data with timeseries analysis,we identified significant periodic signals associated with solar activity(Hale and Schwabe cycles)and ENSO.The results indicate that the alternations of light and dark laminae in the Green River Formation oil shale correspond to alternating dry and wet climate regimes:the light laminae are dominated by carbonate minerals,reflecting drier and milder conditions,while the dark laminae are enriched in terrigenous clastics and organic matter,indicating periods of increased precipitation and warmer temperatures.The detected periodicities(23.5 years,13.3 years and 5.8 years)are highly consistent with modern observations,demonstrating that the lower Eocene Green River oil shale effectively records short-term solar activity and climate variability.Furthermore,our findings confirm that a persistent"permanent El Niño"state did not develop under Early Eocene greenhouse conditions,providing a refined chronological framework for highresolution paleoclimate studies during greenhouse intervals.展开更多
Using multi-source reanalysis data,this study examines the relationship between the tropical Pacific-Atlantic SST Dipole Mode(TPA-DM)and summer precipitation in North China(NCSP)on the interannual timescale during the...Using multi-source reanalysis data,this study examines the relationship between the tropical Pacific-Atlantic SST Dipole Mode(TPA-DM)and summer precipitation in North China(NCSP)on the interannual timescale during the period of 1979-2022.The results show that the TPA-DM,the dominant pattern of interannual variability in the tropical Pacific and Atlantic regions,exhibits a significant negative correlation with NCSP.The positive phase of TPA-DM induces subsidence over the Maritime Continent through a zonal circulation pattern,which initiates a Pacific-Japan-like wave train along the East Asian coast.The circulation anomalies lead to moisture deficits and convergence subsidence over North China,leading to below-normal rainfall.Further analysis reveals that cooler SST in the Southern Tropical Atlantic facilitates the persistence of the TPA-DM by stimulating the anomalous Walker circulation associated with wind-evaporation-SST-convection feedback.展开更多
In this study,based on MERRA-2 reanalysis data and a multi-algorithm integrated atmospheric river(AR)iden-tification method,the authors reveal the cross-seasonal regulation mechanism of El Niño-Southern Oscillati...In this study,based on MERRA-2 reanalysis data and a multi-algorithm integrated atmospheric river(AR)iden-tification method,the authors reveal the cross-seasonal regulation mechanism of El Niño-Southern Oscillation(ENSO)on winter-spring AR activities in East Asia.The results show that ENSO asymmetrically modulates AR ac-tivity through teleconnection and hysteresis effects,and has significant enhancement/inhibition effects on ARs in different regions.At the onset of El Niño,enhanced southwesterly flow at the western edge of the western Pacific subtropical high(WPSH)leads to enhanced AR activity in the western Pacific,and anomalous southerly winds in the Indian Ocean promote northward transport of water vapor in the Arabian Sea and Bay of Bengal.With a three-month lag,the weakening and eastward retreat of the WPSH weakens the low-latitude AR activity,but persistent southerly winds in the Bay of Bengal maintain the AR activity over Southwest China.The mid-to high-latitude AR response exhibits delayed dynamics,initially dominated by the synergistic effect of the southward deviation of the upper-air rapids and the low-level convergence(double-rapid-flow effect)and later modulated by the Pacific-North American teleconnection(PNA)-triggered East Asian ridge,which enhances the precipitation efficiency through prolonged frontal activity and enhanced cold-warm airmass convergence.Overall,El Niño promotes the development of low-and midlatitude AR activity in East Asia,while La Niña promotes(maritime continental)AR activity in the tropics.This study establishes the“ENSO teleconnection→circulation adjust-ment→East Asian AR response”chain,revealing a cross-seasonal lagged response mechanisms of East Asian AR activity,and provides a theoretical basis for winter and spring climate prediction and extreme precipitation forecasting.展开更多
The commencement of the tropical Asian summer monsoon(TASM)in May is a crucial phase in its seasonal evolution,with critical implications for agriculture and water resources.Based on observational and reanalysis data,...The commencement of the tropical Asian summer monsoon(TASM)in May is a crucial phase in its seasonal evolution,with critical implications for agriculture and water resources.Based on observational and reanalysis data,this study finds that the relationship between El Nino-Southern Oscillation(ENSO)and monsoon commencement experiences a notable interdecadal strengthening after 1976/77.While the response of tropical tropospheric temperature to ENSO remains largely unchanged,ENSO induces a stronger Walker circulation,a more pronounced equatorial Rossby wave,and an intensified extratropical Rossby wave train after 1976/77.These enhanced atmospheric processes,which directly reinforce the ENSO-TASM commencement relationship,are likely driven by interdecadal shifts in the structure and variance of ENSO.Post-1976/77,ENSO displays increased variance and a more coherent structure,with more pronounced sea surface temperature anomalies in the western North Pacific and subtropical North Pacific.Given the limitations of observational data,a 1000-year piControl experiment further confirms the role of ENSO variance changes in strengthening its influence on monsoon commencement.Our findings underscore the critical influence of evolving ENSO characteristics on climate anomalies such as monsoon commencement,offering potential insights for short-term climate prediction.展开更多
The Zebiak–Cane(ZC) model, renowned as a coupled ocean-atmosphere model specifically designed to simulate and predict El Ni??o-Southern Oscillation(ENSO), is an indispensable tool for ENSO studies. However, the origi...The Zebiak–Cane(ZC) model, renowned as a coupled ocean-atmosphere model specifically designed to simulate and predict El Ni??o-Southern Oscillation(ENSO), is an indispensable tool for ENSO studies. However, the original ZC model exhibits certain biases in reproducing the ENSO–related sea surface temperature anomalies and heating anomalies, limiting its broader applicability. To improve the accuracy of ENSO simulation, we propose a modified ZC model based on Xie et al.(2015), named the MZC_XJH model, through refining the heating parameterization scheme. The performance in simulating the nonlinear SST–precipitation relationship in the MZC_XJH model is firstly elaborated. Then, we investigate the impacts of three key atmospheric parameters on ENSO simulation by conducting experiments with the MZC_XJH model. Through assessing the performance in simulating five fundamental ENSO metrics(amplitude, periodicity,seasonality, diversity, and skewness), we uncover that the sensitivities of simulated ENSO behaviors to different parameters are distinct. Moreover, we explain why a particular parameter greatly affects some simulated ENSO behaviors while others exert minor influence. We also reveal that the nonlinear effect due to the covariation of multi-parameters on ENSO simulation warrants careful consideration when tuning multi-parameters synchronously. Lastly, we present an updated version of the MZC_XJH model, in which some biases have been mitigated but some remain obvious. Although there are no universally optimal parameters that would ensure flawless performance in simulating every aspect of ENSO, this study provides a valuable reference for tuning atmospheric parameters in the MZC_XJH model, rendering the MZC_XJH model applicable to some research objectives.展开更多
Based on reanalysis data from 1979 to 2021,this study explores the spatial distribution of the Southern Indian Ocean Dipole(SIOD)and its individual and synergistic effects with the El Niño-Southern Oscillation(EN...Based on reanalysis data from 1979 to 2021,this study explores the spatial distribution of the Southern Indian Ocean Dipole(SIOD)and its individual and synergistic effects with the El Niño-Southern Oscillation(ENSO)on summer precipitation in China.The inverse phase spatial distribution of sea surface temperature anomalies(SSTAs)in the southwest and northeast of the southern Indian Ocean is defined as the SIOD.Positive SIOD events(positive SSTAs in the southwest,negative SSTAs in the northeast)are associated with La Niña events(Central Pacific(CP)type),while negative SIOD events(negative SSTAs in the southwest,positive SSTAs in the northeast)are associated with El Niño events(Eastern Pacific(EP)type).Both SIOD and ENSO have certain impacts on summer precipitation in China.Precipitation in the Yangtze River basin decreases,while precipitation in southern China increases during pure positive SIOD(P_PSIOD)events.During pure negative SIOD(P_NSIOD)events,the changes in precipitation are exactly the opposite of those during P_PSIOD events,which may be due to differences in the cross-equatorial flow in the southern Indian Ocean,particularly in low-level Australian cross-equatorial flow.When positive SIOD and CP-type La Niña events occur simultaneously(PSIOD+La_Niña),precipitation increases in the Yangtze-Huaihe River basin,while it decreases in northern China.When negative SIOD and EP-type El Niño events occur simultaneously(NSIOD+El_Niño),precipitation in the Yangtze-Huaihe River basin is significantly lower than during P_NSIOD events.This is caused by differences in water vapor originating from the Pacific Ocean during different events.展开更多
Since Blanford(1884)first linked Himalayan snowfall to subsequent Indian summer monsoon(ISM)rainfall,the potential for long-range forecasting has been recognized.Key advances followed:discovery of the Southern Oscilla...Since Blanford(1884)first linked Himalayan snowfall to subsequent Indian summer monsoon(ISM)rainfall,the potential for long-range forecasting has been recognized.Key advances followed:discovery of the Southern Oscillation(Walker,1925;Walker and Bliss,1932);identification of the Pacific-North American pattern(Wallace and Gutzler,1981);and Bjerknes’(1969)seminal study of ENSO as a predictable climate driver.Foundational theory—including equatorial wave dynamics(Matsuno,1966;Webster,1972;Gill,1980).展开更多
基金supported by the National Natural Science Foundation of China(Grant No.42405029).
文摘Based on reanalysis data and CMIP6 simulations,this study investigates the distinct responses of the cross-equatorial flows(CEFs)over the Maritime Continent(MC)under the simultaneous summer condition of two types of ENSO:central Pacific(CP)and eastern Pacific(EP).Results indicate that CP ENSO tends to exert stronger impacts on CEF.In CP ENSO years,significant lower-level southerly anomalies can be observed across all CEF branches adjacent to MC,accompanied by broader and deeper upper-level northerly anomalies,indicating a well-organized strengthening of both upper-and lowerlevel CEFs.In contrast,CEF anomalies in EP ENSO years tend to be weaker,with significant meridional wind anomalies confined to the east of MC.The disparities in the CEF responses can be elucidated from the perspective of convection over MC,a crucial factor in triggering CEF.In CP ENSO years,westward-leaning sea surface temperature(SST)anomalies result in a distinct cooling in MC and suppressed convection above,driving pronounced CEF anomalies.Conversely,the absence of such organized SST cooling during EP ENSO results in weaker convective forcing and subdued CEF responses.Furthermore,historical simulations from 48 CMIP6 models are utilized to validate the observational findings.Results show that model simulations can successfully reproduce the stronger impacts of CP ENSO,with a remarkable intermodel consistency.This research contributes toward a comprehensive understanding of the diversity in the relationship between CEF and ENSO types,and has implications for seasonal forecasting of CEF variability.
基金supported by the National Key R&D Program of China(Grant No.2023YFF0805100)。
文摘The predictability of a coupled system composed of a coupled reduced-order extratropical ocean-atmosphere model forced by a low-order three-variable tropical recharge-discharge model is explored with emphasis on its long-term forecasting capabilities.Highly idealized ensemble forecasts are produced taking into account the uncertainties in the initial states of the system,with specific attention to the structure of the initial errors in the tropical model.Three main types of experiments are explored:with random perturbations along the three Lyapunov vectors of the tropical model;along the two dominant Lyapunov vectors;and along the first Lyapunov vector only.When perturbations are introduced along all vectors,forecasting biases develop even if in a perfect model framework and with known initial uncertainty properties.Theses biases are considerably reduced only when the perturbations are introduced along the dominant Lyapunov vector.Furthermore,this perturbation strategy allows a reduced mean square error to be obtained at long lead times of a few years,as well as reliable ensemble forecasts across the whole time range.These very counterintuitive findings further underline the importance of appropriately controlling the initial error structure in the tropics through data assimilation.
基金Supported by National Natural Science Foundation of China(Nos.42372125 and 41772092)。
文摘Previous studies have shown that the Eocene oil shale sequences in the Green River Basin contain long-period astronomical age information.The fine-scale chronological characteristics of the oil shale laminae remain largely unexplored.We selected finely laminated oil shales formed in deep-water environments characterized by stable water column stratification as the primary focus of this study,using microscopy and micro-area X-ray fluorescence(μ-XRF)techniques.By integrating high-resolution elemental data with timeseries analysis,we identified significant periodic signals associated with solar activity(Hale and Schwabe cycles)and ENSO.The results indicate that the alternations of light and dark laminae in the Green River Formation oil shale correspond to alternating dry and wet climate regimes:the light laminae are dominated by carbonate minerals,reflecting drier and milder conditions,while the dark laminae are enriched in terrigenous clastics and organic matter,indicating periods of increased precipitation and warmer temperatures.The detected periodicities(23.5 years,13.3 years and 5.8 years)are highly consistent with modern observations,demonstrating that the lower Eocene Green River oil shale effectively records short-term solar activity and climate variability.Furthermore,our findings confirm that a persistent"permanent El Niño"state did not develop under Early Eocene greenhouse conditions,providing a refined chronological framework for highresolution paleoclimate studies during greenhouse intervals.
基金jointly supported by the Second Tibetan Plateau Scientific Expedition and Research Program[grant number-ber 2019QZKK0103]the National Natural Science Foundation of China[grant number 42293294]the China Meteorological Admin-istration Climate Change Special Program[grant number QBZ202303]。
文摘Using multi-source reanalysis data,this study examines the relationship between the tropical Pacific-Atlantic SST Dipole Mode(TPA-DM)and summer precipitation in North China(NCSP)on the interannual timescale during the period of 1979-2022.The results show that the TPA-DM,the dominant pattern of interannual variability in the tropical Pacific and Atlantic regions,exhibits a significant negative correlation with NCSP.The positive phase of TPA-DM induces subsidence over the Maritime Continent through a zonal circulation pattern,which initiates a Pacific-Japan-like wave train along the East Asian coast.The circulation anomalies lead to moisture deficits and convergence subsidence over North China,leading to below-normal rainfall.Further analysis reveals that cooler SST in the Southern Tropical Atlantic facilitates the persistence of the TPA-DM by stimulating the anomalous Walker circulation associated with wind-evaporation-SST-convection feedback.
基金supported by the National Natural Science Foundation of China[grant number 41830964]the Natural Science Foundation of Hunan Province[grant number 2023JJ40666]。
文摘In this study,based on MERRA-2 reanalysis data and a multi-algorithm integrated atmospheric river(AR)iden-tification method,the authors reveal the cross-seasonal regulation mechanism of El Niño-Southern Oscillation(ENSO)on winter-spring AR activities in East Asia.The results show that ENSO asymmetrically modulates AR ac-tivity through teleconnection and hysteresis effects,and has significant enhancement/inhibition effects on ARs in different regions.At the onset of El Niño,enhanced southwesterly flow at the western edge of the western Pacific subtropical high(WPSH)leads to enhanced AR activity in the western Pacific,and anomalous southerly winds in the Indian Ocean promote northward transport of water vapor in the Arabian Sea and Bay of Bengal.With a three-month lag,the weakening and eastward retreat of the WPSH weakens the low-latitude AR activity,but persistent southerly winds in the Bay of Bengal maintain the AR activity over Southwest China.The mid-to high-latitude AR response exhibits delayed dynamics,initially dominated by the synergistic effect of the southward deviation of the upper-air rapids and the low-level convergence(double-rapid-flow effect)and later modulated by the Pacific-North American teleconnection(PNA)-triggered East Asian ridge,which enhances the precipitation efficiency through prolonged frontal activity and enhanced cold-warm airmass convergence.Overall,El Niño promotes the development of low-and midlatitude AR activity in East Asia,while La Niña promotes(maritime continental)AR activity in the tropics.This study establishes the“ENSO teleconnection→circulation adjust-ment→East Asian AR response”chain,revealing a cross-seasonal lagged response mechanisms of East Asian AR activity,and provides a theoretical basis for winter and spring climate prediction and extreme precipitation forecasting.
基金supported jointly by the Natural Science Foundation of Yunnan Province(Grant No.202501CF070059)the National Natural Science Foundation of China(Grant No.42205021)+5 种基金the Yunnan Provincial Science and Technology Department(Grant Nos.202505AB350001 and202403AP140009)the Yunnan Southwest United Graduate School Science and Technology Special Project(Award No.202302AP370003)the Scientific Research Fund Project of Yunnan Education Department(Grant No.2025Y0111)the Practical Innovation Project of Postgraduate Students in the Academic Degree of Yunnan University(Grant No.KC-24248868)the Practical Innovation Project of Postgraduate Students in the Professional Degree of Yunnan University(Grant No.ZC-24248604)the Youth Science and Technology Fund Project of Gansu Province(Grant No.24JRRA1186)。
文摘The commencement of the tropical Asian summer monsoon(TASM)in May is a crucial phase in its seasonal evolution,with critical implications for agriculture and water resources.Based on observational and reanalysis data,this study finds that the relationship between El Nino-Southern Oscillation(ENSO)and monsoon commencement experiences a notable interdecadal strengthening after 1976/77.While the response of tropical tropospheric temperature to ENSO remains largely unchanged,ENSO induces a stronger Walker circulation,a more pronounced equatorial Rossby wave,and an intensified extratropical Rossby wave train after 1976/77.These enhanced atmospheric processes,which directly reinforce the ENSO-TASM commencement relationship,are likely driven by interdecadal shifts in the structure and variance of ENSO.Post-1976/77,ENSO displays increased variance and a more coherent structure,with more pronounced sea surface temperature anomalies in the western North Pacific and subtropical North Pacific.Given the limitations of observational data,a 1000-year piControl experiment further confirms the role of ENSO variance changes in strengthening its influence on monsoon commencement.Our findings underscore the critical influence of evolving ENSO characteristics on climate anomalies such as monsoon commencement,offering potential insights for short-term climate prediction.
基金supported by the National Key Research and Development Program of China (Grant No.2022YFF0802004)the Excellent Youth Natural Science Foundation of Jiangsu Province (BK20230061)+1 种基金the Joint Open Project of KLME&CIC-FEMD (Grant No.KLME202501)Jiangsu Innovation Research Group (Grant No.JSSCTD 202346)。
文摘The Zebiak–Cane(ZC) model, renowned as a coupled ocean-atmosphere model specifically designed to simulate and predict El Ni??o-Southern Oscillation(ENSO), is an indispensable tool for ENSO studies. However, the original ZC model exhibits certain biases in reproducing the ENSO–related sea surface temperature anomalies and heating anomalies, limiting its broader applicability. To improve the accuracy of ENSO simulation, we propose a modified ZC model based on Xie et al.(2015), named the MZC_XJH model, through refining the heating parameterization scheme. The performance in simulating the nonlinear SST–precipitation relationship in the MZC_XJH model is firstly elaborated. Then, we investigate the impacts of three key atmospheric parameters on ENSO simulation by conducting experiments with the MZC_XJH model. Through assessing the performance in simulating five fundamental ENSO metrics(amplitude, periodicity,seasonality, diversity, and skewness), we uncover that the sensitivities of simulated ENSO behaviors to different parameters are distinct. Moreover, we explain why a particular parameter greatly affects some simulated ENSO behaviors while others exert minor influence. We also reveal that the nonlinear effect due to the covariation of multi-parameters on ENSO simulation warrants careful consideration when tuning multi-parameters synchronously. Lastly, we present an updated version of the MZC_XJH model, in which some biases have been mitigated but some remain obvious. Although there are no universally optimal parameters that would ensure flawless performance in simulating every aspect of ENSO, this study provides a valuable reference for tuning atmospheric parameters in the MZC_XJH model, rendering the MZC_XJH model applicable to some research objectives.
基金supported by the National Natural Science Foundation of China[grant numbers 41975087,U2242212,and 41975085]supported by the National Natural Science Foundation of China[grant number U2242212]。
文摘Based on reanalysis data from 1979 to 2021,this study explores the spatial distribution of the Southern Indian Ocean Dipole(SIOD)and its individual and synergistic effects with the El Niño-Southern Oscillation(ENSO)on summer precipitation in China.The inverse phase spatial distribution of sea surface temperature anomalies(SSTAs)in the southwest and northeast of the southern Indian Ocean is defined as the SIOD.Positive SIOD events(positive SSTAs in the southwest,negative SSTAs in the northeast)are associated with La Niña events(Central Pacific(CP)type),while negative SIOD events(negative SSTAs in the southwest,positive SSTAs in the northeast)are associated with El Niño events(Eastern Pacific(EP)type).Both SIOD and ENSO have certain impacts on summer precipitation in China.Precipitation in the Yangtze River basin decreases,while precipitation in southern China increases during pure positive SIOD(P_PSIOD)events.During pure negative SIOD(P_NSIOD)events,the changes in precipitation are exactly the opposite of those during P_PSIOD events,which may be due to differences in the cross-equatorial flow in the southern Indian Ocean,particularly in low-level Australian cross-equatorial flow.When positive SIOD and CP-type La Niña events occur simultaneously(PSIOD+La_Niña),precipitation increases in the Yangtze-Huaihe River basin,while it decreases in northern China.When negative SIOD and EP-type El Niño events occur simultaneously(NSIOD+El_Niño),precipitation in the Yangtze-Huaihe River basin is significantly lower than during P_NSIOD events.This is caused by differences in water vapor originating from the Pacific Ocean during different events.
文摘Since Blanford(1884)first linked Himalayan snowfall to subsequent Indian summer monsoon(ISM)rainfall,the potential for long-range forecasting has been recognized.Key advances followed:discovery of the Southern Oscillation(Walker,1925;Walker and Bliss,1932);identification of the Pacific-North American pattern(Wallace and Gutzler,1981);and Bjerknes’(1969)seminal study of ENSO as a predictable climate driver.Foundational theory—including equatorial wave dynamics(Matsuno,1966;Webster,1972;Gill,1980).
