There is increasing evidence of the possible role of extratropical forcing in the evolution of ENSO. The Southern Hemi- sphere Annular Mode （SAM） is the dominant mode of atmospheric circulation in the Southern Hemis...There is increasing evidence of the possible role of extratropical forcing in the evolution of ENSO. The Southern Hemi- sphere Annular Mode （SAM） is the dominant mode of atmospheric circulation in the Southern Hemisphere extratropics. This study shows that the austral summer （December-January-February; DJF） SAM may also influence the amplitude of ENSO decay during austral autumn （March-April-May; MAM）. The mechanisms associated with this SAM-ENSO relationship can be briefly summarized as follows： The SAM is positively （negatively） correlated with SST in the Southern Hemisphere middle （high） latitudes. This dipole-like SST anomaly pattern is referred to as the Southern Ocean Dipole （SOD）. The DJF SOD, caused by the DJF SAM, could persist until MAM and then influence atmospheric circulation, including trade winds, over the Nifio3.4 area. Anomalous trade winds and SST anomalies over the Nifio3.4 area related to the DJF SAM are further developed through the Bjerkness feedback, which eventually results in a cooling （warming） over the Nifio3.4 area followed by the positive （negative） DJF SAM.展开更多
The increasing trend of the Southern Annular Mode （SAM） in recent decades has influenced climate change in the Southem Hemisphere （SH）.How the SAM will respond increased greenhouse gas concentrations in the future...The increasing trend of the Southern Annular Mode （SAM） in recent decades has influenced climate change in the Southem Hemisphere （SH）.How the SAM will respond increased greenhouse gas concentrations in the future remains uncertain.Understanding the variability of the SAM in the past under a colder climate such as during the Last Glacial Maximum （LGM） might provide some understanding of the response of the SAM under a future warmer climate.We analyzed the changes in the SAM during the LGM in comparison to pre-industrial （PI） simulations using five coupled ocean-atmosphere models （CCSM,FGOALS,IPSL,MIROC,HadCM） from the second phase of the Paleoclimate Modelling Intercomparison Project （PMIP2）.In CCSM,MIROC,IPSL,and FGOALS,the variability of the simulated SAM appears to be reduced in the LGM compared to the PI simulations,with a decrease in the standard deviation of the SAM index.Overall,four out of the five models suggest a weaker SAM amplitude in the LGM consistent with a weaker SH polar vortex and westerly winds found in some proxy records and model analyses.The weakening of the SAM in the LGM was associated with an increase in the vertical propagation of Rossby waves in southern high latitudes.展开更多
The relationships of variations of sea surface temperature anomalies (SSTA) in the South Pacificwith ENSO and Southern Hemisphere Annular Mode (SAM) are examined in the present article byemploying the NCEP-NCAR reanal...The relationships of variations of sea surface temperature anomalies (SSTA) in the South Pacificwith ENSO and Southern Hemisphere Annular Mode (SAM) are examined in the present article byemploying the NCEP-NCAR reanalysis from 1951 to 2006. Two principal modes of South Pacific SSTA areobtained using the EOF (Empirical Orthogonal Function) analysis for austral winter (June, July and August).Our results suggest that EOF1 is closely related with ENSO and EOF2 links to SAM. The EOF1 varieslargely on an interannual and EOF2 on a decadal scale. The time series of coefficients of EOF1 is highlycorrelated simultaneously with Nino3 index. However, the time series of coefficients of EOF2 issignificantly correlated with the March-April-May mean SAM index. Both the EOF1 and EOF2 are found insignificant correlation to summer precipitation over China. With higher-than-normal SSTs in the easternSouth Pacific and simultaneously lower SSTs in the western South Pacific in June-July-August, thesummertime rainfall is found to be less than normal in northern China. As displayed in EOF2 of SSTA, inyears with lower-than-normal SSTs in mid-latitude southern and equatorial eastern Pacific andhigher-than-normal SSTs in the equatorial middle Pacific in March-April-May, the summer precipitation inAugust tends to be more than normal in regions south of Yangtze River.展开更多
The Southern Hemisphere （SH） annular mode （SAM） is the dominant mode of atmospheric circulation in the SH extratropics. The SAM regulates climate in many regions due to its large spatial scale. Exploration of the ...The Southern Hemisphere （SH） annular mode （SAM） is the dominant mode of atmospheric circulation in the SH extratropics. The SAM regulates climate in many regions due to its large spatial scale. Exploration of the climatic impacts of the SAM is a new research field that has developed rapidly in recent years. This paper reviews studies of the climatic impact of the SAM on the SH and the Northern Hemisphere （NH）, emphasizing linkages between the SAM and climate in China. Studies relating the SAM to climate change are also discussed. A general survey of these studies have been systematically investigated. On interannual shows that signals of the SAM in the SH climate scales, the SAM can influence the position of storm tracks and the vertical circulation, and modulate the dynamic and thermodynamic driving effects of the surface wind on the underlying surface, thus influencing the SH air-sea-ice coupled system. These influences generally show zonally symmetrical characteristics, but with local features. On climate change scales, the impacts of the SAM on SH climate change show a similar spatial distribution to those on interannual scales. There are also meaningful results on the relationship between the SAM and the NH climate. The SAM is known to affect the East Asian, West African, and North American summer monsoons, as well as the winter monsoon in China. Air-sea interaction plays an important role in these connections in terms of the storage of the SAM signal and its propagation from the SH to the NH. However, compared with the considerable knowledge of the impact of the SAM on the SH climate, the response of the NH climate to the SAM deserves further study, including both a deep understanding of the propagation mechanism of the SAM signal from the SH to the NH and the establishment of a seasonal prediction model based on the SAM.展开更多
As leading modes of the planetary-scale atmospheric circulation in the extratropics, the Northern Hemisphere(NH)annular mode(NAM) and Southern Hemisphere(SH) annular mode(SAM) are important components of global circul...As leading modes of the planetary-scale atmospheric circulation in the extratropics, the Northern Hemisphere(NH)annular mode(NAM) and Southern Hemisphere(SH) annular mode(SAM) are important components of global circulation, and their variabilities substantially impact the climate in mid-high latitudes. A 35-yr(1979-2013) simulation by the climate system model developed at the Chinese Academy of Meteorological Sciences(CAMS-CSM) was carried out based on observed sea surface temperature and sea ice data. The ability of CAMS-CSM in simulating horizontal and vertical structures of the NAM and SAM, relation of the NAM to the East Asian climate, and temporal variability of the SAM is examined and validated against the observational data. The results show that CAMS-CSM captures the zonally symmetric and out-of-phase variations of sea level pressure anomaly between the midlatitudes and polar zones in the extratropics of the NH and SH. The model has also captured the equivalent barotropic structure in tropospheric geopotential height and the meridional shifts of the NH and SH jet systems associated with the NAM and SAM anomalies. Furthermore, the model is able to reflect the variability of northern and southern Ferrel cells corresponding to the NAM and SAM anomalies. The model reproduces the observed relationship of the boreal winter NAM with the East Asian trough and air temperature over East Asia. It also captures the upward trend of the austral summer SAM index during recent decades. However, compared with the observation, the model shows biases in both the intensity and center locations of the NAM's and SAM's horizontal and vertical structures. Specifically, it overestimates their intensities.展开更多
基金supported by the National Key Research and Development Project[grant number 2020YFA0608902]the Natural Science Foundation of Guangdong Province[grant number 2023A1515010889].
基金supported by the China Special Fund for Meteorological Research in the Public Interest (Grant No.GYHY201506032)an NSFC project (Grant No.41405086)and a National Key R&D Program of China (Grant No.2016YFA0601801)
文摘There is increasing evidence of the possible role of extratropical forcing in the evolution of ENSO. The Southern Hemi- sphere Annular Mode （SAM） is the dominant mode of atmospheric circulation in the Southern Hemisphere extratropics. This study shows that the austral summer （December-January-February; DJF） SAM may also influence the amplitude of ENSO decay during austral autumn （March-April-May; MAM）. The mechanisms associated with this SAM-ENSO relationship can be briefly summarized as follows： The SAM is positively （negatively） correlated with SST in the Southern Hemisphere middle （high） latitudes. This dipole-like SST anomaly pattern is referred to as the Southern Ocean Dipole （SOD）. The DJF SOD, caused by the DJF SAM, could persist until MAM and then influence atmospheric circulation, including trade winds, over the Nifio3.4 area. Anomalous trade winds and SST anomalies over the Nifio3.4 area related to the DJF SAM are further developed through the Bjerkness feedback, which eventually results in a cooling （warming） over the Nifio3.4 area followed by the positive （negative） DJF SAM.
基金supported by the "Investigation of Climate Change Mechanism by Observation and Simulation of Polar Climate Change for the Past and Present" project (PE14010) of the KOPRIthe Special Project of Basic Science and Technology (2011FY120300)+1 种基金the Korea Meteorological Administration Research and Development Program under Grant CATER 2012-3061 (PN13010)supported by the Jiangsu Collaborative Innovation Center for Climate Change
文摘The increasing trend of the Southern Annular Mode （SAM） in recent decades has influenced climate change in the Southem Hemisphere （SH）.How the SAM will respond increased greenhouse gas concentrations in the future remains uncertain.Understanding the variability of the SAM in the past under a colder climate such as during the Last Glacial Maximum （LGM） might provide some understanding of the response of the SAM under a future warmer climate.We analyzed the changes in the SAM during the LGM in comparison to pre-industrial （PI） simulations using five coupled ocean-atmosphere models （CCSM,FGOALS,IPSL,MIROC,HadCM） from the second phase of the Paleoclimate Modelling Intercomparison Project （PMIP2）.In CCSM,MIROC,IPSL,and FGOALS,the variability of the simulated SAM appears to be reduced in the LGM compared to the PI simulations,with a decrease in the standard deviation of the SAM index.Overall,four out of the five models suggest a weaker SAM amplitude in the LGM consistent with a weaker SH polar vortex and westerly winds found in some proxy records and model analyses.The weakening of the SAM in the LGM was associated with an increase in the vertical propagation of Rossby waves in southern high latitudes.
基金Natural Science Foundation of China(41105056,41175062)"Qinglan"Project of Jiangsu Province for Activating Research TeamsPriority Academic Program Development of Jiangsu Province Higher Education Institutions
文摘The relationships of variations of sea surface temperature anomalies (SSTA) in the South Pacificwith ENSO and Southern Hemisphere Annular Mode (SAM) are examined in the present article byemploying the NCEP-NCAR reanalysis from 1951 to 2006. Two principal modes of South Pacific SSTA areobtained using the EOF (Empirical Orthogonal Function) analysis for austral winter (June, July and August).Our results suggest that EOF1 is closely related with ENSO and EOF2 links to SAM. The EOF1 varieslargely on an interannual and EOF2 on a decadal scale. The time series of coefficients of EOF1 is highlycorrelated simultaneously with Nino3 index. However, the time series of coefficients of EOF2 issignificantly correlated with the March-April-May mean SAM index. Both the EOF1 and EOF2 are found insignificant correlation to summer precipitation over China. With higher-than-normal SSTs in the easternSouth Pacific and simultaneously lower SSTs in the western South Pacific in June-July-August, thesummertime rainfall is found to be less than normal in northern China. As displayed in EOF2 of SSTA, inyears with lower-than-normal SSTs in mid-latitude southern and equatorial eastern Pacific andhigher-than-normal SSTs in the equatorial middle Pacific in March-April-May, the summer precipitation inAugust tends to be more than normal in regions south of Yangtze River.
基金Supported by the National Basic Research and Development(973)Program of China(2013CB430200)National Natural Science Foundation of China(41030961)China Meteorological Administration Special Public Welfare Research Fund(GYHY201306031)
文摘The Southern Hemisphere （SH） annular mode （SAM） is the dominant mode of atmospheric circulation in the SH extratropics. The SAM regulates climate in many regions due to its large spatial scale. Exploration of the climatic impacts of the SAM is a new research field that has developed rapidly in recent years. This paper reviews studies of the climatic impact of the SAM on the SH and the Northern Hemisphere （NH）, emphasizing linkages between the SAM and climate in China. Studies relating the SAM to climate change are also discussed. A general survey of these studies have been systematically investigated. On interannual shows that signals of the SAM in the SH climate scales, the SAM can influence the position of storm tracks and the vertical circulation, and modulate the dynamic and thermodynamic driving effects of the surface wind on the underlying surface, thus influencing the SH air-sea-ice coupled system. These influences generally show zonally symmetrical characteristics, but with local features. On climate change scales, the impacts of the SAM on SH climate change show a similar spatial distribution to those on interannual scales. There are also meaningful results on the relationship between the SAM and the NH climate. The SAM is known to affect the East Asian, West African, and North American summer monsoons, as well as the winter monsoon in China. Air-sea interaction plays an important role in these connections in terms of the storage of the SAM signal and its propagation from the SH to the NH. However, compared with the considerable knowledge of the impact of the SAM on the SH climate, the response of the NH climate to the SAM deserves further study, including both a deep understanding of the propagation mechanism of the SAM signal from the SH to the NH and the establishment of a seasonal prediction model based on the SAM.
基金Supported by the National Natural Science Foundation of China(41775084 and 41405102)National Key Research and Development Program of China(2018YFC1505706)Basic Research Special Project of Chinese Academy of Meteorological Sciences(2019Z008)
文摘As leading modes of the planetary-scale atmospheric circulation in the extratropics, the Northern Hemisphere(NH)annular mode(NAM) and Southern Hemisphere(SH) annular mode(SAM) are important components of global circulation, and their variabilities substantially impact the climate in mid-high latitudes. A 35-yr(1979-2013) simulation by the climate system model developed at the Chinese Academy of Meteorological Sciences(CAMS-CSM) was carried out based on observed sea surface temperature and sea ice data. The ability of CAMS-CSM in simulating horizontal and vertical structures of the NAM and SAM, relation of the NAM to the East Asian climate, and temporal variability of the SAM is examined and validated against the observational data. The results show that CAMS-CSM captures the zonally symmetric and out-of-phase variations of sea level pressure anomaly between the midlatitudes and polar zones in the extratropics of the NH and SH. The model has also captured the equivalent barotropic structure in tropospheric geopotential height and the meridional shifts of the NH and SH jet systems associated with the NAM and SAM anomalies. Furthermore, the model is able to reflect the variability of northern and southern Ferrel cells corresponding to the NAM and SAM anomalies. The model reproduces the observed relationship of the boreal winter NAM with the East Asian trough and air temperature over East Asia. It also captures the upward trend of the austral summer SAM index during recent decades. However, compared with the observation, the model shows biases in both the intensity and center locations of the NAM's and SAM's horizontal and vertical structures. Specifically, it overestimates their intensities.
