With a hybrid atmosphere-ocean coupled model we carried out an experimental forecast of a well documented Madden-Julian Oscillation (MJO) event that was observed during the period of Tropical Ocean Global Atmosphere C...With a hybrid atmosphere-ocean coupled model we carried out an experimental forecast of a well documented Madden-Julian Oscillation (MJO) event that was observed during the period of Tropical Ocean Global Atmosphere Coupled Ocean-Atmosphere Response Experiment (TOGA-COARE). The observed event, originated in the western Indian Ocean around 6 January 1993, moved eastward with a phase speed of about 6.2 m s 1 and reached the dateline around February 1. The hybrid coupled model reasonably forecasts the MJO initiation in the western Indian Ocean, but the predicted MJO event propagates too slow (～ 4.4 m s 1 ). Results from previous observational studies using unprecedented humidity profiles obtained by NASA Aqua/AIRS satellite suggested that two potential physical processes may be responsible for this model caveat. After improving the cumulus parameterization scheme based on the observations, the model is able to forecast the same event one month ahead. Further sensitivity experiment confirms that the speed-up of model MJO propagation is primarily due to the improved convective scheme. Further, air-sea coupling plays an important role in maintaining the intensity of the predicted MJO. The results here suggest that MJO prediction skill is sensitive to model cumulus parameterization and air-sea coupling.展开更多
A 600-year pre-industrial simulation with Bergen Climate Model(BCM)Version 2 is used to investigate the linkage between winter Arctic Oscillation(AO)and the Southeast Asian summer monsoon(SEASM)on the inter-decadal ti...A 600-year pre-industrial simulation with Bergen Climate Model(BCM)Version 2 is used to investigate the linkage between winter Arctic Oscillation(AO)and the Southeast Asian summer monsoon(SEASM)on the inter-decadal timescale.The results indicate an in-phase relationship between the AO and SEASM with periods of approximately 16–32 and 60–80 years.During the positive phase of winter AO,an anomalous surface anti-cyclonic atmosphere circulation appears over North Pacific in winter.The corresponding anomalies in ocean circulation and surface heat flux,particularly the latent and sensible heat flux,resemble a negative Pacific Decadal Oscillation(PDO)-like sea surface temperature(SST)pattern.The AO-associated PDO-like winter SST can persist into summer and can therefore lead to inter-decadal variability of summer monsoon rainfall in East and Southeast Asia.展开更多
A simple approach that considers both internal decadal variability and the effect of anthropogenic forcing is developed to predict the decadal components of global sea surface temperatures (SSTs) for the three decades...A simple approach that considers both internal decadal variability and the effect of anthropogenic forcing is developed to predict the decadal components of global sea surface temperatures (SSTs) for the three decades 2011-2040. The internal decadal component is derived by harmonic wave expansion analyses based on the quasiperiodic evolution of the Pacific Decadal Oscillation (PDO) and the Atlantic Multidecadal Oscillation (AMO), as obtained from observational SST datasets. Furthermore, the external decadal component induced by anthropogenic forcing is assessed with a second-order fit based on the ensemble of projected SSTs in the experiments with multiple coupled climate models associated with the third Coupled Model Intercomparison Project (CMIP3) under the Intergovernmental Panels on Climate Change (IPCC) Special Reports on Emissions Scenario (SRES) A1B. A validation for the years from 2002 to 2010 based on a comparison of the predicted and the observed SST and their spatial correlation, as well as the root mean square error (RMSE), suggests that the approach is reasonable overall. In addition, the predicted results over the 50°S-50°N global band, the Indian Ocean, the western Pacific Ocean, the tropical eastern Pacific Ocean, and the North and the South Atlantic Ocean are presented.展开更多
The internal modes of the North Pacific can lead to climatic oscillations through ocean-atmosphere interactions and induce global climate responses.The best example is the Pacific Decadal Oscillation, but this fails t...The internal modes of the North Pacific can lead to climatic oscillations through ocean-atmosphere interactions and induce global climate responses.The best example is the Pacific Decadal Oscillation, but this fails to explain many climate phenomena. Here, another multidecadal variability over the North Pacific is described, found by analyzing reconstructed data covering the past 140 years. It is named the Pacific Multidecadal Oscillation （PMO）, with anomalously high/low SSTs over the northeastern Pacific, and a quasi-60-year cycle. Related to this low-frequency variability of SST, the global mean temperature and precipitation present significant interdecadal differences. More importantly, the PMO index leads the global mean surface air temperature and SST by one to three years. The Arctic Oscillation pattern and atmospheric circulations are shown to change substantially with the transition of the PMO mode from positive to negative phases. This multidecadal oscillation improves the prospect for a long-term forecast of the global warming trend, since the PMO bears a remarkable relationship with global temperature.展开更多
The decadal variation of the intensity of the interannual opposite connection （seesaw） between the Somali and Australian cross-equatorial flows （CEFs） is investigated. During the period prior to the mid-1960s, and...The decadal variation of the intensity of the interannual opposite connection （seesaw） between the Somali and Australian cross-equatorial flows （CEFs） is investigated. During the period prior to the mid-1960s, and after the early-2000s, the intensity of the interannual seesaw connection is significantly weaker relative to the period between. Such interdecadal shifts in the interannual seesaw intensity bear a resemblance to the decadal shift in ENSO＇s strength, and can be further attributed to the phase transition of the Atlantic Multidecadal Oscillation （AMO）. When the AMO is in a positive phase, the ENSO amplitude reduces and the seesaw strength becomes weakened, and vice versa.The historical simulation outputs of the CMIP5 models are used to verify the connection, and a similar result was obtained. Thus, the notion that the intensity of the interannual opposite connection （seesaw） between the CEFs is modulated by the AMO is robust.展开更多
The drying trend in the South Asian summer monsoon(SASM)area has been a focus of monsoon rainfall studies in the last two decades.However,this study reveals that a signi cant interdecadal change in the SASM rainfall o...The drying trend in the South Asian summer monsoon(SASM)area has been a focus of monsoon rainfall studies in the last two decades.However,this study reveals that a signi cant interdecadal change in the SASM rainfall occurred in approximately the year 2000.Obvious spatial inhomo-geneity was a feature of this change,with increased rainfall over the southern part of the India Pakistan border area that extends from the Arabian Sea,as well as in the western Bay of Bengal.Furthermore,there was decreased rainfall over the southern SASM and the western coast of the Indian Peninsula.Numerical experiments using CAM4 show that global SST changes can induce general changes in the SASM circulation consistent with observations.The tropical Pacific/Indian Ocean SST anomalies dominated the Walker and the regional Hadley circulation changes,respectively,while the descending motion anomalies over the southern SASM were further enhanced by the warmer tropical Atlantic SSTs.Moreover,the spatial inhomogeneity of this interdecadal change in the SASM rainfall needs further study.展开更多
Indian Summer Monsoon Rainfall （ISMR） exhibits a prominent inter-annual variability known as troposphere biennial oscillation.A season of deficient June to September monsoon rainfall in India is followed by warm sea...Indian Summer Monsoon Rainfall （ISMR） exhibits a prominent inter-annual variability known as troposphere biennial oscillation.A season of deficient June to September monsoon rainfall in India is followed by warm sea surface temperature （SST） anomalies over the tropical Indian Ocean and cold SST anomalies over the westem Pacific Ocean.These anomalies persist until the following monsoon,which yields normal or excessive rainfall.Monsoon rainfall in India has shown decadal variability in the form of 30 year epochs of alternately occurring frequent and infrequent drought monsoons since 1841,when rainfall measurements began in India.Decadal oscillations of monsoon rainfall and the well known decadal oscillations in SSTs of the Atlantic and Pacific oceans have the same period of approximately 60 years and nearly the same temporal phase.In both of these variabilities,anomalies in monsoon heat source,such as deep convection,and middle latitude westerlies of the upper troposphere over south Asia have prominent roles.展开更多
Equatorial central Pacific precipitation experienced a prominent decline in the late 1990 s.This change was previously attributed to a La Nina-like mean sea surface temperature(SST)change in the Pacific Ocean associat...Equatorial central Pacific precipitation experienced a prominent decline in the late 1990 s.This change was previously attributed to a La Nina-like mean sea surface temperature(SST)change in the Pacific Ocean associated with a phase switch of the Interdecadal Pacific Oscillation.Here,using a series of model experiments,the authors reveal that the El Nino-related interannual SST anomalies contributed largely to the precipitation decrease over the equatorial central Pacific.This El Nino SST effect was due to the change in the amplitude of El Nino events in the late 1990 s.The 1980-98 decade had more large-amplitude El Nino events than the 1999-2014 decade.The nonlinear precipitation response to SST anomalies resulted in a larger decadal mean precipitation in the 1980-98 decade than in the 1999-2014 decade.The results highlight the importance of El Nino amplitude change in future climate change related to global warming.展开更多
t A frequency-specified empirical orthogonal function （FSEOF） analysis is proposed in this study. The aim of FSEOF is to specify a prescribed-band of frequency in leading principal components with less information l...t A frequency-specified empirical orthogonal function （FSEOF） analysis is proposed in this study. The aim of FSEOF is to specify a prescribed-band of frequency in leading principal components with less information losing at the ends of the data, thus well characterizing the signals of interest. The FSEOF can well capture prescribed variability in leading modes, and has intrinsic merits in resolving frequency-related modes, especially those associated with low frequency oscillations. An application of the FSEOF to the tropical and northern Pacific sea surface temperature shows that this new method can successfully separate Pacific decadal oscillation （PDO） mode from the El Nino-Southern oscillation mode, and clearly detect all regime shifts of PDO in the past century.展开更多
基金supported by NASA Earth Science Program, NSF Climate Dynamics Programthe Japan Agency for Marine-Earth Science and Technology (JAMSTEC), NASA+1 种基金NOAA through their sponsorship of the IPRCsupported by APEC Climate Center (APCC) as a part of APCC international research project
文摘With a hybrid atmosphere-ocean coupled model we carried out an experimental forecast of a well documented Madden-Julian Oscillation (MJO) event that was observed during the period of Tropical Ocean Global Atmosphere Coupled Ocean-Atmosphere Response Experiment (TOGA-COARE). The observed event, originated in the western Indian Ocean around 6 January 1993, moved eastward with a phase speed of about 6.2 m s 1 and reached the dateline around February 1. The hybrid coupled model reasonably forecasts the MJO initiation in the western Indian Ocean, but the predicted MJO event propagates too slow (～ 4.4 m s 1 ). Results from previous observational studies using unprecedented humidity profiles obtained by NASA Aqua/AIRS satellite suggested that two potential physical processes may be responsible for this model caveat. After improving the cumulus parameterization scheme based on the observations, the model is able to forecast the same event one month ahead. Further sensitivity experiment confirms that the speed-up of model MJO propagation is primarily due to the improved convective scheme. Further, air-sea coupling plays an important role in maintaining the intensity of the predicted MJO. The results here suggest that MJO prediction skill is sensitive to model cumulus parameterization and air-sea coupling.
基金supported by the National Basic Research Program of China(Grant No.2012CB955401)the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDA05110203)the Center for Climate Dynamics(Project:Integrated Model-data Approach for Understanding Multidecadal Natural Climate Variability)
文摘A 600-year pre-industrial simulation with Bergen Climate Model(BCM)Version 2 is used to investigate the linkage between winter Arctic Oscillation(AO)and the Southeast Asian summer monsoon(SEASM)on the inter-decadal timescale.The results indicate an in-phase relationship between the AO and SEASM with periods of approximately 16–32 and 60–80 years.During the positive phase of winter AO,an anomalous surface anti-cyclonic atmosphere circulation appears over North Pacific in winter.The corresponding anomalies in ocean circulation and surface heat flux,particularly the latent and sensible heat flux,resemble a negative Pacific Decadal Oscillation(PDO)-like sea surface temperature(SST)pattern.The AO-associated PDO-like winter SST can persist into summer and can therefore lead to inter-decadal variability of summer monsoon rainfall in East and Southeast Asia.
基金supported by the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant Nos.XDA05090406 and XDA05110203)the special projects of the China Meteorological Administration(Grant No.GYHY201006022)contribution to the DecCen and Blue Arc projects funded by the Research Council of Norway and to the Centre for Climate Dynamics at the Bjerknes Centre
文摘A simple approach that considers both internal decadal variability and the effect of anthropogenic forcing is developed to predict the decadal components of global sea surface temperatures (SSTs) for the three decades 2011-2040. The internal decadal component is derived by harmonic wave expansion analyses based on the quasiperiodic evolution of the Pacific Decadal Oscillation (PDO) and the Atlantic Multidecadal Oscillation (AMO), as obtained from observational SST datasets. Furthermore, the external decadal component induced by anthropogenic forcing is assessed with a second-order fit based on the ensemble of projected SSTs in the experiments with multiple coupled climate models associated with the third Coupled Model Intercomparison Project (CMIP3) under the Intergovernmental Panels on Climate Change (IPCC) Special Reports on Emissions Scenario (SRES) A1B. A validation for the years from 2002 to 2010 based on a comparison of the predicted and the observed SST and their spatial correlation, as well as the root mean square error (RMSE), suggests that the approach is reasonable overall. In addition, the predicted results over the 50°S-50°N global band, the Indian Ocean, the western Pacific Ocean, the tropical eastern Pacific Ocean, and the North and the South Atlantic Ocean are presented.
基金supported by the National Natural Science Foundation of China[grant number 41421004],[grant number41130103]
文摘The internal modes of the North Pacific can lead to climatic oscillations through ocean-atmosphere interactions and induce global climate responses.The best example is the Pacific Decadal Oscillation, but this fails to explain many climate phenomena. Here, another multidecadal variability over the North Pacific is described, found by analyzing reconstructed data covering the past 140 years. It is named the Pacific Multidecadal Oscillation （PMO）, with anomalously high/low SSTs over the northeastern Pacific, and a quasi-60-year cycle. Related to this low-frequency variability of SST, the global mean temperature and precipitation present significant interdecadal differences. More importantly, the PMO index leads the global mean surface air temperature and SST by one to three years. The Arctic Oscillation pattern and atmospheric circulations are shown to change substantially with the transition of the PMO mode from positive to negative phases. This multidecadal oscillation improves the prospect for a long-term forecast of the global warming trend, since the PMO bears a remarkable relationship with global temperature.
基金supported by the National Key Basic Research Program of China[grant number 973 Program,2015CB453202]the National Natural Science Foundation of China[grant number 41375085],[grant number 41421004]
文摘The decadal variation of the intensity of the interannual opposite connection （seesaw） between the Somali and Australian cross-equatorial flows （CEFs） is investigated. During the period prior to the mid-1960s, and after the early-2000s, the intensity of the interannual seesaw connection is significantly weaker relative to the period between. Such interdecadal shifts in the interannual seesaw intensity bear a resemblance to the decadal shift in ENSO＇s strength, and can be further attributed to the phase transition of the Atlantic Multidecadal Oscillation （AMO）. When the AMO is in a positive phase, the ENSO amplitude reduces and the seesaw strength becomes weakened, and vice versa.The historical simulation outputs of the CMIP5 models are used to verify the connection, and a similar result was obtained. Thus, the notion that the intensity of the interannual opposite connection （seesaw） between the CEFs is modulated by the AMO is robust.
基金supported by the National Key Research and Development Program of China [grant number2017YFC1502304]the National Natural Science Foundation of China [grant numbers 41675083 and 41522503]the Chinese Academy of Sciences–Peking University Joint Research Program
文摘The drying trend in the South Asian summer monsoon(SASM)area has been a focus of monsoon rainfall studies in the last two decades.However,this study reveals that a signi cant interdecadal change in the SASM rainfall occurred in approximately the year 2000.Obvious spatial inhomo-geneity was a feature of this change,with increased rainfall over the southern part of the India Pakistan border area that extends from the Arabian Sea,as well as in the western Bay of Bengal.Furthermore,there was decreased rainfall over the southern SASM and the western coast of the Indian Peninsula.Numerical experiments using CAM4 show that global SST changes can induce general changes in the SASM circulation consistent with observations.The tropical Pacific/Indian Ocean SST anomalies dominated the Walker and the regional Hadley circulation changes,respectively,while the descending motion anomalies over the southern SASM were further enhanced by the warmer tropical Atlantic SSTs.Moreover,the spatial inhomogeneity of this interdecadal change in the SASM rainfall needs further study.
基金the European Commission(Project INDO-MARECLIM)the Norwegian Research Council(Project INDIA-CLIM)for providing financial support for this study
文摘Indian Summer Monsoon Rainfall （ISMR） exhibits a prominent inter-annual variability known as troposphere biennial oscillation.A season of deficient June to September monsoon rainfall in India is followed by warm sea surface temperature （SST） anomalies over the tropical Indian Ocean and cold SST anomalies over the westem Pacific Ocean.These anomalies persist until the following monsoon,which yields normal or excessive rainfall.Monsoon rainfall in India has shown decadal variability in the form of 30 year epochs of alternately occurring frequent and infrequent drought monsoons since 1841,when rainfall measurements began in India.Decadal oscillations of monsoon rainfall and the well known decadal oscillations in SSTs of the Atlantic and Pacific oceans have the same period of approximately 60 years and nearly the same temporal phase.In both of these variabilities,anomalies in monsoon heat source,such as deep convection,and middle latitude westerlies of the upper troposphere over south Asia have prominent roles.
基金supported by the National Key Research and Development Program of China [grant number2016YFA0600603]the National Natural Science Foundation of China [grant numbers 41775080,41530425,41721004,and 41475081]
文摘Equatorial central Pacific precipitation experienced a prominent decline in the late 1990 s.This change was previously attributed to a La Nina-like mean sea surface temperature(SST)change in the Pacific Ocean associated with a phase switch of the Interdecadal Pacific Oscillation.Here,using a series of model experiments,the authors reveal that the El Nino-related interannual SST anomalies contributed largely to the precipitation decrease over the equatorial central Pacific.This El Nino SST effect was due to the change in the amplitude of El Nino events in the late 1990 s.The 1980-98 decade had more large-amplitude El Nino events than the 1999-2014 decade.The nonlinear precipitation response to SST anomalies resulted in a larger decadal mean precipitation in the 1980-98 decade than in the 1999-2014 decade.The results highlight the importance of El Nino amplitude change in future climate change related to global warming.
基金supported by the National Basic Research Program(Grant No.2013CB430302)the National Program on Global Change and Air-Sea Interaction(Grant Nos. GASI-IPOVAI-04 & GASI-IPOVAI-06)+2 种基金the National Natural Science Foundation of China(Grant Nos.41506025 & 41530961)the Project of State Key Laboratory of Satellite Ocean Environment Dynamics,Second Institute of Oceanography(Grant No.SOEDZZ1504)the project of Second Institute of Oceanography,SOA(Grant No.QNYC201501)
文摘t A frequency-specified empirical orthogonal function （FSEOF） analysis is proposed in this study. The aim of FSEOF is to specify a prescribed-band of frequency in leading principal components with less information losing at the ends of the data, thus well characterizing the signals of interest. The FSEOF can well capture prescribed variability in leading modes, and has intrinsic merits in resolving frequency-related modes, especially those associated with low frequency oscillations. An application of the FSEOF to the tropical and northern Pacific sea surface temperature shows that this new method can successfully separate Pacific decadal oscillation （PDO） mode from the El Nino-Southern oscillation mode, and clearly detect all regime shifts of PDO in the past century.
