In recent years,there has been an increasing need for climate information across diverse sectors of society.This demand has arisen from the necessity to adapt to and mitigate the impacts of climate variability and cha...In recent years,there has been an increasing need for climate information across diverse sectors of society.This demand has arisen from the necessity to adapt to and mitigate the impacts of climate variability and change.Likewise,this period has seen a significant increase in our understanding of the physical processes and mechanisms that drive precipitation and its variability across different regions of Africa.By leveraging a large volume of climate model outputs,numerous studies have investigated the model representation of African precipitation as well as underlying physical processes.These studies have assessed whether the physical processes are well depicted and whether the models are fit for informing mitigation and adaptation strategies.This paper provides a review of the progress in precipitation simulation overAfrica in state-of-the-science climate models and discusses the major issues and challenges that remain.展开更多
Climate models are essential for understanding past,present,and future changes in atmospheric circulation,with circulation modes providing key sources of seasonal predictability and prediction uncertainties for both g...Climate models are essential for understanding past,present,and future changes in atmospheric circulation,with circulation modes providing key sources of seasonal predictability and prediction uncertainties for both global and regional climates.This study assesses the performance of models participating in phase 6 of the Coupled Model Intercomparison Project in simulating interannual variability modes of Northern Hemisphere 500-hPa geopotential height during winter and summer,distinguishing predictable(potentially predictable on seasonal or longer timescales)and unpredictable(intraseasonal and essentially unpredictable at long range)components,using reanalysis data and a variance decomposition method.Although most models effectively capture unpredictable modes in reanalysis,their ability to reproduce dominant predictable modes-specifically the Pacific-North American pattern,Arctic Oscillation,and Western Pacific Oscillation in winter,and the East Atlantic and North Atlantic Oscillations in summer-varies notably.An optimal ensemble is identified to distinguish(a)predictable-external modes,dominated by external forcing,and(b)predictable-internal modes,associated with slow internal variability,during the historical period(1950-2014)and the SSP5-8.5 scenario(2036-2100).Under increased radiative forcing,the leading winter/summer predictable-external mode exhibits a more uniform spatial distribution,remarkably larger trend and annual variance,and enhanced height-sea surface temperature(SST)covariance under SSP5-8.5 compared to historical conditions.The dominant winter/summer predictable-internal modes also exhibit increased variance and height-SST covariance under SSP5-8.5,along with localized changes in spatial configuration.Minimal changes are observed in spatial distribution or variance for dominant winter/summer unpredictable modes under SSP5-8.5.This study,from a predictive perspective,deepens our understanding of model uncertainties and projected changes in circulations.展开更多
Despite its significant societal and scientific importance,projected changes in the characteristics of intraseasonal oscillations(ISOs)associated with Indian summer monsoon rainfall under increased greenhouse gas conc...Despite its significant societal and scientific importance,projected changes in the characteristics of intraseasonal oscillations(ISOs)associated with Indian summer monsoon rainfall under increased greenhouse gas concentrations remain largely unexplored.This study utilizes downscaled and bias-corrected historical simulations and projections from 17 CMIP6 models to investigate the future evolution of ISOs.Our findings reveal a twofold increase in ISO variability over India in the far future under the very high emissions scenario,raising critical concerns about its adverse socioeconomic impacts.Our analysis suggests that the increased magnitude of precipitation anomalies associated with northwardpropagating ISOs may intensify active monsoon spells,potentially triggering extreme rainfall events.Additionally,the phase speed of these northward-propagating ISOs over the Bay of Bengal is projected to accelerate owing to weakened air-sea coupling and feedback.This acceleration reduces the northwest-southeast tilt of the precipitation band,altering the spatial structure of the ISOs.Concurrently,the strengthening of circulation-precipitation feedback and warming of the Indian Ocean are projected to enhance the phase speed of monsoon ISOs,leading to more frequent active spells.This study underscores the critical role of regional ocean-atmosphere feedback in shaping future ISO characteristics,highlighting the urgent need for improved understanding and prediction of these changes in the context of a warming climate.展开更多
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
Global climate change is a pressing environmental challenge.Climate-induced migration highlights the severe impact of unsuitable climatic conditions.However,current research methods are limited in their ability to ass...Global climate change is a pressing environmental challenge.Climate-induced migration highlights the severe impact of unsuitable climatic conditions.However,current research methods are limited in their ability to assess climate suitability for residents in high-altitude areas.In this study,we assess climate suitability across the Qinghai-Xizang Plateau from 1979 to 2018 and project future changes using four different Shared Socioeconomic Pathway(SSP)climate scenarios by constructing the Climate Suitability Index(CSI).The findings reveal a notable increase in CSI from 0.32 to 0.36 from 1979 to 2018.The primary factors contributing to the increased climate suitability are increasing annual mean precipitation(61.42%)and decreasing solar radiation(17.22%)from 1979 to 2018.Furthermore,the study forecasts a continued enhancement of climate suitability across all SSP scenarios,with SSP585 demonstrating the greatest improvement,followed by SSP370,SSP245,and SSP126.Although low oxygen levels at high altitudes remain a challenge,the overall improvement in climate suitability offers hope for people living at high altitudes to cope with climate change.展开更多
基金the World Climate Research Programme(WCRP),Climate Variability and Predictability(CLIVAR),and Global Energy and Water Exchanges(GEWEX)for facilitating the coordination of African monsoon researchsupport from the Center for Earth System Modeling,Analysis,and Data at the Pennsylvania State Universitythe support of the Office of Science of the U.S.Department of Energy Biological and Environmental Research as part of the Regional&Global Model Analysis(RGMA)program area。
文摘In recent years,there has been an increasing need for climate information across diverse sectors of society.This demand has arisen from the necessity to adapt to and mitigate the impacts of climate variability and change.Likewise,this period has seen a significant increase in our understanding of the physical processes and mechanisms that drive precipitation and its variability across different regions of Africa.By leveraging a large volume of climate model outputs,numerous studies have investigated the model representation of African precipitation as well as underlying physical processes.These studies have assessed whether the physical processes are well depicted and whether the models are fit for informing mitigation and adaptation strategies.This paper provides a review of the progress in precipitation simulation overAfrica in state-of-the-science climate models and discusses the major issues and challenges that remain.
基金supported by the National Natural Science Foundation of China(Grant Nos.U2342210 and 42275043)the National Institute of Natural Hazards,Ministry of Emergency Management of China(Grant Nos.J2223806,ZDJ2024-25 and ZDJ2025-34)。
文摘Climate models are essential for understanding past,present,and future changes in atmospheric circulation,with circulation modes providing key sources of seasonal predictability and prediction uncertainties for both global and regional climates.This study assesses the performance of models participating in phase 6 of the Coupled Model Intercomparison Project in simulating interannual variability modes of Northern Hemisphere 500-hPa geopotential height during winter and summer,distinguishing predictable(potentially predictable on seasonal or longer timescales)and unpredictable(intraseasonal and essentially unpredictable at long range)components,using reanalysis data and a variance decomposition method.Although most models effectively capture unpredictable modes in reanalysis,their ability to reproduce dominant predictable modes-specifically the Pacific-North American pattern,Arctic Oscillation,and Western Pacific Oscillation in winter,and the East Atlantic and North Atlantic Oscillations in summer-varies notably.An optimal ensemble is identified to distinguish(a)predictable-external modes,dominated by external forcing,and(b)predictable-internal modes,associated with slow internal variability,during the historical period(1950-2014)and the SSP5-8.5 scenario(2036-2100).Under increased radiative forcing,the leading winter/summer predictable-external mode exhibits a more uniform spatial distribution,remarkably larger trend and annual variance,and enhanced height-sea surface temperature(SST)covariance under SSP5-8.5 compared to historical conditions.The dominant winter/summer predictable-internal modes also exhibit increased variance and height-SST covariance under SSP5-8.5,along with localized changes in spatial configuration.Minimal changes are observed in spatial distribution or variance for dominant winter/summer unpredictable modes under SSP5-8.5.This study,from a predictive perspective,deepens our understanding of model uncertainties and projected changes in circulations.
文摘Despite its significant societal and scientific importance,projected changes in the characteristics of intraseasonal oscillations(ISOs)associated with Indian summer monsoon rainfall under increased greenhouse gas concentrations remain largely unexplored.This study utilizes downscaled and bias-corrected historical simulations and projections from 17 CMIP6 models to investigate the future evolution of ISOs.Our findings reveal a twofold increase in ISO variability over India in the far future under the very high emissions scenario,raising critical concerns about its adverse socioeconomic impacts.Our analysis suggests that the increased magnitude of precipitation anomalies associated with northwardpropagating ISOs may intensify active monsoon spells,potentially triggering extreme rainfall events.Additionally,the phase speed of these northward-propagating ISOs over the Bay of Bengal is projected to accelerate owing to weakened air-sea coupling and feedback.This acceleration reduces the northwest-southeast tilt of the precipitation band,altering the spatial structure of the ISOs.Concurrently,the strengthening of circulation-precipitation feedback and warming of the Indian Ocean are projected to enhance the phase speed of monsoon ISOs,leading to more frequent active spells.This study underscores the critical role of regional ocean-atmosphere feedback in shaping future ISO characteristics,highlighting the urgent need for improved understanding and prediction of these changes in the context of a warming climate.
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funded by the Second Tibetan Plateau Scientific Expedition and Research(STEP)program(Grant No.2019QZKK0608).
文摘Global climate change is a pressing environmental challenge.Climate-induced migration highlights the severe impact of unsuitable climatic conditions.However,current research methods are limited in their ability to assess climate suitability for residents in high-altitude areas.In this study,we assess climate suitability across the Qinghai-Xizang Plateau from 1979 to 2018 and project future changes using four different Shared Socioeconomic Pathway(SSP)climate scenarios by constructing the Climate Suitability Index(CSI).The findings reveal a notable increase in CSI from 0.32 to 0.36 from 1979 to 2018.The primary factors contributing to the increased climate suitability are increasing annual mean precipitation(61.42%)and decreasing solar radiation(17.22%)from 1979 to 2018.Furthermore,the study forecasts a continued enhancement of climate suitability across all SSP scenarios,with SSP585 demonstrating the greatest improvement,followed by SSP370,SSP245,and SSP126.Although low oxygen levels at high altitudes remain a challenge,the overall improvement in climate suitability offers hope for people living at high altitudes to cope with climate change.
