利用1979—2012年逐月Hadley中心海表温度、欧洲中期天气预报中心次表层海温、NCEP/NCAR风场再分析资料,对两类中太平洋（CP）El Nino及耦合的大气环流特征进行分析。结果表明,第一类CP El Nino（CP-ⅠEl Nino）增暖中心位于Nino4区且...利用1979—2012年逐月Hadley中心海表温度、欧洲中期天气预报中心次表层海温、NCEP/NCAR风场再分析资料,对两类中太平洋（CP）El Nino及耦合的大气环流特征进行分析。结果表明,第一类CP El Nino（CP-ⅠEl Nino）增暖中心位于Nino4区且关于赤道对称;第二类CP El Nino（CP-ⅡEl Nino）的Nino4区与热带东北太平洋区域（NEP,130-110°W、15-25°N）同位相变化,冬季成熟后形成关于赤道非对称的带状增暖结构。进一步的研究表明,两类CP El Nino次表层结构存在差异：CP-ⅠEl Nino冬季次表层海温异常（SOTA）在中东太平洋与西太平洋呈显著偶极分布;CP-ⅡEl Nino在中、西太平洋位相相反但东太平洋异常较弱,且经向异常主要在赤道及其以北。两类CP El Nino耦合的大气环流特征不同：CP-ⅠEl Nino冬季异常Walker环流上升中心位于赤道上空,经向风向赤道辐合,低纬地区Hadley环流加强;CP-ⅡEl Nino冬季低层向北越赤道气流加强,Walker环流上升中心移到赤道以北,低纬地区Hadley环流减弱。展开更多
利用观测资料及模式结果探讨了EP/CP El Nino事件对华南前汛期(4-6月)降水异常的影响。结果发现,EP和CP型相关的华南前汛期降水异常分布之间存在明显月际差异,表现为4、5月EP(CP)型相关的降水异常以偏多(少)为主;6月则相反,EP(CP)型的...利用观测资料及模式结果探讨了EP/CP El Nino事件对华南前汛期(4-6月)降水异常的影响。结果发现,EP和CP型相关的华南前汛期降水异常分布之间存在明显月际差异,表现为4、5月EP(CP)型相关的降水异常以偏多(少)为主;6月则相反,EP(CP)型的降水呈负(正)异常分布。分析表明,EP型相关的4、5月偏强的副热带高压与850hPa上西北太平洋反气旋异常相配合,有利于水汽从海洋向陆地输送,且两广地区水汽辐合,降水异常偏多;而6月相关的500hPa异常场上对应偏强的东亚大槽,不利于水汽输送,且广东地区处于水汽辐散区,对应降水偏少。CP型相关的4、5月对应500hPa上东亚大槽偏强,不利于水汽往陆地输送,且华南为水汽辐散,降水偏少;6月的500hPa上呈现“+-+”的东亚-太平洋遥相关波列(EAP)型,华南地区为明显的水汽辐合,降水偏多。GFDL模式较好地再现了EP/CP型的4、5月降水异常分布及大气环流形势,但是对6月的模拟存在一定偏差。展开更多
利用1951—2017年NOAA月平均海面温度、NCEP/NCAR的再分析资料以及中国160站月降水观测资料,通过分类合成分析方法研究了东部型(eastern Pacific,EP)和中部型(central Pacific,CP)厄尔尼诺(El Nino)事件当年及次年对山东夏季降水年际变...利用1951—2017年NOAA月平均海面温度、NCEP/NCAR的再分析资料以及中国160站月降水观测资料,通过分类合成分析方法研究了东部型(eastern Pacific,EP)和中部型(central Pacific,CP)厄尔尼诺(El Nino)事件当年及次年对山东夏季降水年际变化的影响。结果表明,两类El Nino发生年,山东夏季降水均较常年显著偏少,但EP El Nino对山东夏季降水的影响强度和范围略弱于CP El Nino:EP El Nino发生年夏季,仅鲁西北部分地区以及胶州湾附近降水较常年显著偏少,而CP El Nino当年夏季山东全区降水较常年显著偏少。EP El Nino和CP El Nino次年对山东夏季降水异常的影响呈反位相,且影响大值区空间位置也完全相反:EP El Nino次年夏季山东东部尤其是半岛地区降水较常年异常偏少(青岛地区最为突出),而CP El Nino次年夏季山东中部和北部尤其是西北部地区降水较常年异常偏多。EP El Nino当年和次年夏季、CP El Nino当年夏季500 hPa高度场异常分布形势不利于西北太平洋副热带高压的北上,850 hPa风场为偏北风和偏东风异常,山东水汽输送条件差,水汽无明显辐合,造成大部分地区降水偏少。CP El Nino次年夏季西北太平洋副热带高压偏强,位置偏西偏北,850 hPa显著西南风场异常,山东中西部水汽辐合明显,这些是降水偏多的重要原因。展开更多
采用1960~2014年西南地区93个站的逐月降水资料以及NCEP/NCAR再分析月平均资料,分析了东部型El Ni?o(EP El Ni?o)和中部型El Ni?o(CP El Ni?o)对我国西南地区冬季降水的不同影响。结果表明, EP El Ni?o年冬季和CP El Ni?o事件中1994/199...采用1960~2014年西南地区93个站的逐月降水资料以及NCEP/NCAR再分析月平均资料,分析了东部型El Ni?o(EP El Ni?o)和中部型El Ni?o(CP El Ni?o)对我国西南地区冬季降水的不同影响。结果表明, EP El Ni?o年冬季和CP El Ni?o事件中1994/1995年、2002/2003年冬季,我国西南地区受异常偏东风影响,获得来自孟加拉湾和南海的水汽供应。同时,西南地区存在明显的幅合上升运动,上升运动异常增强,对流加强,导致西南地区冬季降水偏多;而CP El Ni?o事件中1968/1969年、1977/1978年,2004/2005年、2009/2010年冬季,我国西南地区受异常西北风影响,来自孟加拉湾和南海的水汽减少。同时,西南地区存在明显的幅散下沉运动,上升运动异常减弱,对流减弱,导致西南地区冬季降水偏少。展开更多
The tropical Pacific has begun to experience a new type of El Nio, which has occurred particularly frequently during the last decade, referred to as the central Pacific(CP) El Nio. Various coupled models with differen...The tropical Pacific has begun to experience a new type of El Nio, which has occurred particularly frequently during the last decade, referred to as the central Pacific(CP) El Nio. Various coupled models with different degrees of complexity have been used to make real-time El Nio predictions, but high uncertainty still exists in their forecasts. It remains unknown as to how much of this uncertainty is specifically related to the new CP-type El Nio and how much is common to both this type and the conventional Eastern Pacific(EP)-type El Nio. In this study, the deterministic performance of an El Nio–Southern Oscillation(ENSO) ensemble prediction system is examined for the two types of El Nio. Ensemble hindcasts are run for the nine EP El Nio events and twelve CP El Nio events that have occurred since 1950. The results show that(1) the skill scores for the EP events are significantly better than those for the CP events, at all lead times;(2) the systematic forecast biases come mostly from the prediction of the CP events; and(3) the systematic error is characterized by an overly warm eastern Pacific during the spring season, indicating a stronger spring prediction barrier for the CP El Nio. Further improvements to coupled atmosphere–ocean models in terms of CP El Nio prediction should be recognized as a key and high-priority task for the climate prediction community.展开更多
Aims The Amazon basin plays an important role in the global carbon budget.Interannual climate variability associated with El Nino can affect the Amazon ecosystem carbon balance.In recent years,studies have suggested t...Aims The Amazon basin plays an important role in the global carbon budget.Interannual climate variability associated with El Nino can affect the Amazon ecosystem carbon balance.In recent years,studies have suggested that there are two different types of El Ninos:eastern-Pacific(EP)El Nino and central-Pacific(CP)El Nino.The impacts of two types of El Nino on the Amazon climate and Amazon ecosystem are analyzed in the study.Methods A composite method has been applied to highlight the common features for the EP-and CP-El Nino events using observational data,IPCC-AR4 model output.Potential impacts of the two different types of El Nino on ecosystem carbon sequestration over the Amazon have been investigated using a process-based biogeochemical model,the Biome–BioGeochemical Cycles model(Biome–BGC).Important Findings Below-normal rainfall is observed year round in northern,central and eastern Amazonia during EP-El Nino years.During CP-El Nino years,negative rainfall anomalies are observed in most of the Amazon during the austral summer wet season,while there is average or above-average precipitation in other seasons.EP-and CP-El Nino events produce strikingly different precipitation anomaly pattern in the tropical and subtropical Andes during the austral fall season:wetter conditions prevail during EP-El Nino years and drier conditions during CP-El Nino years.Temperatures are above-average year round throughout tropical South America during EP-El Nino events,especially during austral summer.During CP-El Nino events,average or slightly above-average temperatures prevail in the tropics,but these temperatures are less extreme than EP year’s temperature except in austral fall.These precipitation and temperature anomalies influence ecosystem productivity and carbon sequestration throughout the Amazon.Using the Biome–BGC model,we find that net ecosystem production(NEP)in the EP-El Nino years is below average,in agreement with most previous studies;such results indicate that the Amazon region acts as a net carbon source to the atmosphere during EP-El Nino years.In the CP-El Nino years,NEP does not differ significantly from its climatological value,suggesting that the Amazon forest remains a carbon sink for the atmosphere.Thus,even if CP-El Nino events increase in frequency or amplitude under global warming climate as predicted in some Global Climate Models,the Amazon rainforest may remain a carbon sink to the atmosphere during El Nino years in the near future.展开更多
文摘利用1979—2012年逐月Hadley中心海表温度、欧洲中期天气预报中心次表层海温、NCEP/NCAR风场再分析资料,对两类中太平洋（CP）El Nino及耦合的大气环流特征进行分析。结果表明,第一类CP El Nino（CP-ⅠEl Nino）增暖中心位于Nino4区且关于赤道对称;第二类CP El Nino（CP-ⅡEl Nino）的Nino4区与热带东北太平洋区域（NEP,130-110°W、15-25°N）同位相变化,冬季成熟后形成关于赤道非对称的带状增暖结构。进一步的研究表明,两类CP El Nino次表层结构存在差异：CP-ⅠEl Nino冬季次表层海温异常（SOTA）在中东太平洋与西太平洋呈显著偶极分布;CP-ⅡEl Nino在中、西太平洋位相相反但东太平洋异常较弱,且经向异常主要在赤道及其以北。两类CP El Nino耦合的大气环流特征不同：CP-ⅠEl Nino冬季异常Walker环流上升中心位于赤道上空,经向风向赤道辐合,低纬地区Hadley环流加强;CP-ⅡEl Nino冬季低层向北越赤道气流加强,Walker环流上升中心移到赤道以北,低纬地区Hadley环流减弱。
文摘利用观测资料及模式结果探讨了EP/CP El Nino事件对华南前汛期(4-6月)降水异常的影响。结果发现,EP和CP型相关的华南前汛期降水异常分布之间存在明显月际差异,表现为4、5月EP(CP)型相关的降水异常以偏多(少)为主;6月则相反,EP(CP)型的降水呈负(正)异常分布。分析表明,EP型相关的4、5月偏强的副热带高压与850hPa上西北太平洋反气旋异常相配合,有利于水汽从海洋向陆地输送,且两广地区水汽辐合,降水异常偏多;而6月相关的500hPa异常场上对应偏强的东亚大槽,不利于水汽输送,且广东地区处于水汽辐散区,对应降水偏少。CP型相关的4、5月对应500hPa上东亚大槽偏强,不利于水汽往陆地输送,且华南为水汽辐散,降水偏少;6月的500hPa上呈现“+-+”的东亚-太平洋遥相关波列(EAP)型,华南地区为明显的水汽辐合,降水偏多。GFDL模式较好地再现了EP/CP型的4、5月降水异常分布及大气环流形势,但是对6月的模拟存在一定偏差。
文摘利用1951—2017年NOAA月平均海面温度、NCEP/NCAR的再分析资料以及中国160站月降水观测资料,通过分类合成分析方法研究了东部型(eastern Pacific,EP)和中部型(central Pacific,CP)厄尔尼诺(El Nino)事件当年及次年对山东夏季降水年际变化的影响。结果表明,两类El Nino发生年,山东夏季降水均较常年显著偏少,但EP El Nino对山东夏季降水的影响强度和范围略弱于CP El Nino:EP El Nino发生年夏季,仅鲁西北部分地区以及胶州湾附近降水较常年显著偏少,而CP El Nino当年夏季山东全区降水较常年显著偏少。EP El Nino和CP El Nino次年对山东夏季降水异常的影响呈反位相,且影响大值区空间位置也完全相反:EP El Nino次年夏季山东东部尤其是半岛地区降水较常年异常偏少(青岛地区最为突出),而CP El Nino次年夏季山东中部和北部尤其是西北部地区降水较常年异常偏多。EP El Nino当年和次年夏季、CP El Nino当年夏季500 hPa高度场异常分布形势不利于西北太平洋副热带高压的北上,850 hPa风场为偏北风和偏东风异常,山东水汽输送条件差,水汽无明显辐合,造成大部分地区降水偏少。CP El Nino次年夏季西北太平洋副热带高压偏强,位置偏西偏北,850 hPa显著西南风场异常,山东中西部水汽辐合明显,这些是降水偏多的重要原因。
文摘采用1960~2014年西南地区93个站的逐月降水资料以及NCEP/NCAR再分析月平均资料,分析了东部型El Ni?o(EP El Ni?o)和中部型El Ni?o(CP El Ni?o)对我国西南地区冬季降水的不同影响。结果表明, EP El Ni?o年冬季和CP El Ni?o事件中1994/1995年、2002/2003年冬季,我国西南地区受异常偏东风影响,获得来自孟加拉湾和南海的水汽供应。同时,西南地区存在明显的幅合上升运动,上升运动异常增强,对流加强,导致西南地区冬季降水偏多;而CP El Ni?o事件中1968/1969年、1977/1978年,2004/2005年、2009/2010年冬季,我国西南地区受异常西北风影响,来自孟加拉湾和南海的水汽减少。同时,西南地区存在明显的幅散下沉运动,上升运动异常减弱,对流减弱,导致西南地区冬季降水偏少。
基金supported by the National Program for Support of Top-notch Young Professionalsthe National Natural Science Foundation of China (Grant No. 41576019)J.-Y. YU was supported by the US National Science Foundation (Grant No. AGS-150514)
文摘The tropical Pacific has begun to experience a new type of El Nio, which has occurred particularly frequently during the last decade, referred to as the central Pacific(CP) El Nio. Various coupled models with different degrees of complexity have been used to make real-time El Nio predictions, but high uncertainty still exists in their forecasts. It remains unknown as to how much of this uncertainty is specifically related to the new CP-type El Nio and how much is common to both this type and the conventional Eastern Pacific(EP)-type El Nio. In this study, the deterministic performance of an El Nio–Southern Oscillation(ENSO) ensemble prediction system is examined for the two types of El Nio. Ensemble hindcasts are run for the nine EP El Nio events and twelve CP El Nio events that have occurred since 1950. The results show that(1) the skill scores for the EP events are significantly better than those for the CP events, at all lead times;(2) the systematic forecast biases come mostly from the prediction of the CP events; and(3) the systematic error is characterized by an overly warm eastern Pacific during the spring season, indicating a stronger spring prediction barrier for the CP El Nio. Further improvements to coupled atmosphere–ocean models in terms of CP El Nio prediction should be recognized as a key and high-priority task for the climate prediction community.
文摘Aims The Amazon basin plays an important role in the global carbon budget.Interannual climate variability associated with El Nino can affect the Amazon ecosystem carbon balance.In recent years,studies have suggested that there are two different types of El Ninos:eastern-Pacific(EP)El Nino and central-Pacific(CP)El Nino.The impacts of two types of El Nino on the Amazon climate and Amazon ecosystem are analyzed in the study.Methods A composite method has been applied to highlight the common features for the EP-and CP-El Nino events using observational data,IPCC-AR4 model output.Potential impacts of the two different types of El Nino on ecosystem carbon sequestration over the Amazon have been investigated using a process-based biogeochemical model,the Biome–BioGeochemical Cycles model(Biome–BGC).Important Findings Below-normal rainfall is observed year round in northern,central and eastern Amazonia during EP-El Nino years.During CP-El Nino years,negative rainfall anomalies are observed in most of the Amazon during the austral summer wet season,while there is average or above-average precipitation in other seasons.EP-and CP-El Nino events produce strikingly different precipitation anomaly pattern in the tropical and subtropical Andes during the austral fall season:wetter conditions prevail during EP-El Nino years and drier conditions during CP-El Nino years.Temperatures are above-average year round throughout tropical South America during EP-El Nino events,especially during austral summer.During CP-El Nino events,average or slightly above-average temperatures prevail in the tropics,but these temperatures are less extreme than EP year’s temperature except in austral fall.These precipitation and temperature anomalies influence ecosystem productivity and carbon sequestration throughout the Amazon.Using the Biome–BGC model,we find that net ecosystem production(NEP)in the EP-El Nino years is below average,in agreement with most previous studies;such results indicate that the Amazon region acts as a net carbon source to the atmosphere during EP-El Nino years.In the CP-El Nino years,NEP does not differ significantly from its climatological value,suggesting that the Amazon forest remains a carbon sink for the atmosphere.Thus,even if CP-El Nino events increase in frequency or amplitude under global warming climate as predicted in some Global Climate Models,the Amazon rainforest may remain a carbon sink to the atmosphere during El Nino years in the near future.
