Based on global monthly average data set of sea surface temperature (SST) during 1950 - 1992 and global monthly average 500 hPa height during 1930- 1997 offered by NCARINCEP, the feature of SST anomaly in the Atlantic...Based on global monthly average data set of sea surface temperature (SST) during 1950 - 1992 and global monthly average 500 hPa height during 1930- 1997 offered by NCARINCEP, the feature of SST anomaly in the Atlantic and its relation with summer precipitation over the Northeast China are analyzed. The results show that, the second eigenvector of the SST’s empirical orthogonal expanssion in winter season over the North Atlantic suggests that dist-ibution of SST anomaly has unusual meridional difference; The location of its center is basically identical to center of significant correlation region be- tween summer precipitation over the Northeast China and winter SST in the Atlantic. When winter SST in the North Atlantic is hot in south and cold in north, the blocking situation is stronger in the middle- high latitude. Correspondingly, the blocking high pressure in the northern North Pacific is also getting stronger, the westerlies circulation index in East Asia in next summer would be lower,as a result,more precipitation in the summer would be experienced over Northeast China and vice versa.展开更多
Based on the NCEP/NCAR reanalysis global SST, 500-hPa geopotential height, 850-hPa wind monthly mean data and summer precipitation from 80 observation stations of Northeast China for the period 1961-2000, the summer p...Based on the NCEP/NCAR reanalysis global SST, 500-hPa geopotential height, 850-hPa wind monthly mean data and summer precipitation from 80 observation stations of Northeast China for the period 1961-2000, the summer precipitation field of Northeast China was decomposed by using the principal component analysis method, then the relationships between the first three precipitation leading modes and the global SSTA in preceding seasons were studied, and the responses of the 500-hPa atmospheric circulation in East Asia to the preceding winter SSTA in north Pacific and its influence on the summer precipitation in Northeast China were probed. The results show that the SSTA, especially the ENSO event in preceding seasons has really very important influence on the occurrence of the whole coincident precipitation episode in Northeast China, and relates to the precipitation episodes of the reverse variation in south-north and in west-east direction closely. The north Pacific SST anomalies in preceding winters are associated with the summer precipitation in Northeast China through its influence on the western Pacific subtropical high and the East Asia subtropical monsoon in summer. Therefore, taking the global SSTA distribution in preceding seasons, especially the ENSO event, as the precursor signal to predict the precipitation anomaly in Northeast China has good reliability and definite indicative significance.展开更多
A statistical downscaling approach based on multiple-linear-regression(MLR) for the prediction of summer precipitation anomaly in southeastern China was established,which was based on the outputs of seven operational ...A statistical downscaling approach based on multiple-linear-regression(MLR) for the prediction of summer precipitation anomaly in southeastern China was established,which was based on the outputs of seven operational dynamical models of Development of a European Multi-model Ensemble System for Seasonal to Interannual Prediction(DEMETER) and observed data.It was found that the anomaly correlation coefficients(ACCs) spatial pattern of June-July-August(JJA) precipitation over southeastern China between the seven models and the observation were increased significantly;especially in the central and the northeastern areas,the ACCs were all larger than 0.42(above 95% level) and 0.53(above 99% level).Meanwhile,the root-mean-square errors(RMSE) were reduced in each model along with the multi-model ensemble(MME) for some of the stations in the northeastern area;additionally,the value of RMSE difference between before and after downscaling at some stations were larger than 1 mm d-1.Regionally averaged JJA rainfall anomaly temporal series of the downscaling scheme can capture the main characteristics of observation,while the correlation coefficients(CCs) between the temporal variations of the observation and downscaling results varied from 0.52 to 0.69 with corresponding variations from-0.27 to 0.22 for CCs between the observation and outputs of the models.展开更多
Using NCEP/NCAR reanalysis data and monthly precipitation over 160 conventional stations in China, analyses of moisture transport characteristics and corresponding precipitation variation in the east part of China in ...Using NCEP/NCAR reanalysis data and monthly precipitation over 160 conventional stations in China, analyses of moisture transport characteristics and corresponding precipitation variation in the east part of China in summer are made, and studies are carried out on possible influence on moisture transport and precipitation in summer by the variation of Antarctic Oscillation (AAO). The results show that the abnormal variation of the AAO affected the summer precipitation in China significantly. The variation of AAO can cause the variation of intension and location of Northwestern Pacific High, which in turn cause the variation of summer monsoon rainfall in the eastern China.展开更多
Based on Reanalysis datasets from National Centers for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) and summer rainfall datasets from China National Climate Center (NCC), by using tren...Based on Reanalysis datasets from National Centers for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) and summer rainfall datasets from China National Climate Center (NCC), by using trend analysis and composite analysis methods, the relationship between the reduction of summer precipitation in North China and northern hemispheric circulation changes was investigated. The results show that summer rainfall in North China had a significant decreasing tendency, especially true since 1965 in which an abrupt change occurred. The northern hemisphere atmospheric circulation at 500 hPa had a remarkable change after 1965, from outstanding meridional circulation to outstanding zonal circulation, leading to upper trough activity to decrease, resulting in the rainfall weather processes caused by upward motion behind trough significantly to reduce. At 500 hPa in Mongolian region, air temperature decreased, resulting in lower troposphere pressure to increase, leading to low pressure activity significantly to decrease and rainfall weather processes influencing North China to reduce. At the same time, the decreased air temperature in 500 hPa would caused the upper troposphere geopotential height to reduce, resulting in high–altitude jet southerly location, the East Asian summer monsoon to weaken, then it was difficult for water vapor transport to cross the Yangtze River valley and reach the North China region, with a southerly summer monsoon rainfall zone. The summer precipitation reduction in North China had a good correlation with the northern hemispheric circulation changes.展开更多
The spring atmospheric heat source(AHS)over the Tibetan Plateau(TP)has been suggested to affect the Asian summer monsoon and summer precipitation over South China.However,its influence on the summer precipitation in N...The spring atmospheric heat source(AHS)over the Tibetan Plateau(TP)has been suggested to affect the Asian summer monsoon and summer precipitation over South China.However,its influence on the summer precipitation in Northeast China(NEC)remains unknown.The connection between spring TP AHS and subsequent summer precipitation over NEC from 1961 to 2020 is analyzed in this study.Results illustrate that stronger spring TP AHS can enhance subsequent summer NEC precipitation,and higher soil moisture in the Yellow River Valley-North China region(YRVNC)acts as a bridge.During spring,the strong TP AHS could strengthen the transportation of water vapor to East China and lead to excessive rainfall in the YRVNC.Thus,soil moisture increases,which regulates local thermal conditions by decreasing local surface skin temperature and sensible heat.Owing to the memory of soil moisture,the lower spring sensible heat over the YRVNC can last until mid-summer,decrease the land–sea thermal contrast,and weaken the southerly winds over the East Asia–western Pacific region and convective activities over the South China Sea and tropical western Pacific.This modulates the East Asia–Pacific teleconnection pattern,which leads to a cyclonic anomaly and excessive summer precipitation over NEC.展开更多
Sea surface temperature anomaly(SSTA)is a major signal for prediction of summer precipitation in East Asia.The relationship between SSTA in the tropical oceans and summer precipitation in East Asia has been documented...Sea surface temperature anomaly(SSTA)is a major signal for prediction of summer precipitation in East Asia.The relationship between SSTA in the tropical oceans and summer precipitation in East Asia has been documented in many studies.However,the relationship between SSTA and late summer(July–August)precipitation(JAP)over Northeast China(NEC)on the interannual timescale has received little attention.In this study,we examine the relationship between Indian Ocean Basin warming(IOBW)anomalies in spring and the JAP in NEC since the early1960 s.A significant positive correlation is found between the spring IOBW index and JAP over NEC.The positive spring IOBW anomaly is followed by an anomalous anticyclone from Northwest Pacific to the Korean Peninsula.This anomalous anticyclone favors a significantly strong and northward western Pacific subtropical high(WPSH),which facilitates anomalous southerly winds over NEC and the transport of more water vapor into this region.Further analysis indicates that the spring IOBW anomalies have important impacts on the vertical air motion in the tropics and subtropics during the summer.Significant anomalous upward(downward)motion covering Indonesia(Northwest Pacific to the southern Korean Peninsula)occurs when the IOBW is in its positive phase,which favors the northward movement of the WPSH in late summer and more precipitation over NEC in July–August.Modulation of the atmospheric circulation by this mechanism further influences the JAP over NEC.展开更多
The variations of regional mean daily precipitation extreme (RMDPE) events in central China and associated circulation anomalies during June, July, and August (JJA) of 1961-2010 are investigated by using daily in-...The variations of regional mean daily precipitation extreme (RMDPE) events in central China and associated circulation anomalies during June, July, and August (JJA) of 1961-2010 are investigated by using daily in-situ precipitation observations and the NCEP/NCAR reanalysis data. The precipitation data were collected at 239 state-level stations distributed throughout the provinces of Henan, Hubei, and Hunan. During 1961-2010, the 99th percentile threshold for RMDPE is 23.585 mm day-1. The number of RMDPE events varies on both interannual and interdecadal timescales, and increases significantly after the mid 1980s. The RMDPE events happen most frequently between late June and mid July, and are generally associated with anomalous baroclinic tropospheric circulations. The supply of moisture to the southern part of central China comes in a stepping way from the outer-region of an abnormal anticyclone over the Bay of Bengal and the South China Sea. Fluxes of wave activity generated over the northeastern Tibetan Plateau converge over central China, which favors the genesis and maintenance of wave disturbances over the region. RMDPE events typically occur in tandem with a strong heating gradient formed by net heating in central China and the large-scale net cooling in the surrounding area. The occurrence of RMDPE events over central China is tied to anomalous local cyclonic circulations, topographic forcing over the northeast Tibetan Plateau, and anomalous gradients of diabatic heating between central China and the surrounding areas.展开更多
为改进华北夏季降水异常的预测能力、寻找前期异常信号的监测预测指标,本文利用1961-2020年华北、华南夏季降水资料,美国环境预报中心和大气科学研究中心(National Centers for Environmental Prediction/National Center for Atmospher...为改进华北夏季降水异常的预测能力、寻找前期异常信号的监测预测指标,本文利用1961-2020年华北、华南夏季降水资料,美国环境预报中心和大气科学研究中心(National Centers for Environmental Prediction/National Center for Atmospheric Research,NCEP/NCAR)的再分析环流资料、向外长波辐射资料(Outgoing Longwave Radiation,OLR),采用相关、合成和环流异常回归重构等方法,分析了华南前汛期(5-6月)降水异常与华北夏季(7-8月)降水异常的联系。结果表明:(1)华北夏季(7-8月)降水异常通常与华南前汛期(5-6月)降水异常呈反位相关系,即如果华南前汛期降水偏多,对应华北夏季降水就会偏少,反之亦然。华南前汛期降水异常可以作为华北夏季降水异常监测预测的一个前期指标。东亚夏季风造成对流层低层水汽输送异常和北半球夏季热带低频信号传播造成对流层中低层环流异常是两地降水呈反位相变化的联系机制。(2)在水汽输送方面,如果5-6月东亚副热带夏季风偏强,即东亚西南南风(SSW)显著偏强,华南水汽来源会偏少,造成华南前汛期(5-6月)降水异常偏少。到7-8月,印度夏季风显著偏强、东亚副热带夏季风进一步增强,华北水汽来源显著偏多,造成华北夏季(7-8月)降水异常偏多。反之,华南前汛期(5-6月)降水异常偏多,华北夏季(7-8月)降水异常偏少。(3)在动力环流方面,如果5-6月,热带印度洋低频信号活跃、西北太平洋低频信号不活跃,伴随印度洋低频信号向东北方向传播,在850 hPa层华南沿海附近形成反气旋性环流异常,对流减弱,造成华南前汛期(5-6月)降水偏少。到7-8月,热带印度洋低频信号仍然十分活跃,原来位于华南沿海的反气旋性环流异常向东北方向传播到长江下游至东部海上,反气旋北侧的华北地区为气旋性环流,对流偏强;另一方面,伴随低频扰动在对流层中高层向高纬传播,会形成沿高空西风急流传播的扰动波列,扰动位置相对固定,在贝加尔湖附近为负距平、朝鲜半岛附近为正距平,造成贝加尔湖高空槽加深、副热带高压在朝鲜半岛附近加强,形成“东高西低”的阻挡形势,有利于华北产生上升运动。即华北夏季对流上升运动增强,造成华北夏季(7-8月)降水偏多。反之,华南前汛期(5-6月)降水偏多,华北夏季(7-8月)降水偏少。(4)华南前汛期降水异常对华北夏季降水异常有很好的指示意义。但在有些年份关系并不好,这可能是因为这种关系还受到其他因子如海温变化、热带环流、青藏高原以及中高纬环流变化的调节与影响。展开更多
文摘Based on global monthly average data set of sea surface temperature (SST) during 1950 - 1992 and global monthly average 500 hPa height during 1930- 1997 offered by NCARINCEP, the feature of SST anomaly in the Atlantic and its relation with summer precipitation over the Northeast China are analyzed. The results show that, the second eigenvector of the SST’s empirical orthogonal expanssion in winter season over the North Atlantic suggests that dist-ibution of SST anomaly has unusual meridional difference; The location of its center is basically identical to center of significant correlation region be- tween summer precipitation over the Northeast China and winter SST in the Atlantic. When winter SST in the North Atlantic is hot in south and cold in north, the blocking situation is stronger in the middle- high latitude. Correspondingly, the blocking high pressure in the northern North Pacific is also getting stronger, the westerlies circulation index in East Asia in next summer would be lower,as a result,more precipitation in the summer would be experienced over Northeast China and vice versa.
文摘Based on the NCEP/NCAR reanalysis global SST, 500-hPa geopotential height, 850-hPa wind monthly mean data and summer precipitation from 80 observation stations of Northeast China for the period 1961-2000, the summer precipitation field of Northeast China was decomposed by using the principal component analysis method, then the relationships between the first three precipitation leading modes and the global SSTA in preceding seasons were studied, and the responses of the 500-hPa atmospheric circulation in East Asia to the preceding winter SSTA in north Pacific and its influence on the summer precipitation in Northeast China were probed. The results show that the SSTA, especially the ENSO event in preceding seasons has really very important influence on the occurrence of the whole coincident precipitation episode in Northeast China, and relates to the precipitation episodes of the reverse variation in south-north and in west-east direction closely. The north Pacific SST anomalies in preceding winters are associated with the summer precipitation in Northeast China through its influence on the western Pacific subtropical high and the East Asia subtropical monsoon in summer. Therefore, taking the global SSTA distribution in preceding seasons, especially the ENSO event, as the precursor signal to predict the precipitation anomaly in Northeast China has good reliability and definite indicative significance.
基金supported by the special Fund for Public Welfare Industry (Meteorology) (Grant No. GYHY200906018)the National Basic Research Program of China (Grant Nos. 2010CB950304 and 2009CB421406)the Knowl-edge Innovation Program of the Chinese Academy of Sciences (Grant No. KZCX2-YW-QN202)
文摘A statistical downscaling approach based on multiple-linear-regression(MLR) for the prediction of summer precipitation anomaly in southeastern China was established,which was based on the outputs of seven operational dynamical models of Development of a European Multi-model Ensemble System for Seasonal to Interannual Prediction(DEMETER) and observed data.It was found that the anomaly correlation coefficients(ACCs) spatial pattern of June-July-August(JJA) precipitation over southeastern China between the seven models and the observation were increased significantly;especially in the central and the northeastern areas,the ACCs were all larger than 0.42(above 95% level) and 0.53(above 99% level).Meanwhile,the root-mean-square errors(RMSE) were reduced in each model along with the multi-model ensemble(MME) for some of the stations in the northeastern area;additionally,the value of RMSE difference between before and after downscaling at some stations were larger than 1 mm d-1.Regionally averaged JJA rainfall anomaly temporal series of the downscaling scheme can capture the main characteristics of observation,while the correlation coefficients(CCs) between the temporal variations of the observation and downscaling results varied from 0.52 to 0.69 with corresponding variations from-0.27 to 0.22 for CCs between the observation and outputs of the models.
基金Under the auspices of the National Natural Science Foundation of China (No. 40233037)
文摘Using NCEP/NCAR reanalysis data and monthly precipitation over 160 conventional stations in China, analyses of moisture transport characteristics and corresponding precipitation variation in the east part of China in summer are made, and studies are carried out on possible influence on moisture transport and precipitation in summer by the variation of Antarctic Oscillation (AAO). The results show that the abnormal variation of the AAO affected the summer precipitation in China significantly. The variation of AAO can cause the variation of intension and location of Northwestern Pacific High, which in turn cause the variation of summer monsoon rainfall in the eastern China.
文摘Based on Reanalysis datasets from National Centers for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) and summer rainfall datasets from China National Climate Center (NCC), by using trend analysis and composite analysis methods, the relationship between the reduction of summer precipitation in North China and northern hemispheric circulation changes was investigated. The results show that summer rainfall in North China had a significant decreasing tendency, especially true since 1965 in which an abrupt change occurred. The northern hemisphere atmospheric circulation at 500 hPa had a remarkable change after 1965, from outstanding meridional circulation to outstanding zonal circulation, leading to upper trough activity to decrease, resulting in the rainfall weather processes caused by upward motion behind trough significantly to reduce. At 500 hPa in Mongolian region, air temperature decreased, resulting in lower troposphere pressure to increase, leading to low pressure activity significantly to decrease and rainfall weather processes influencing North China to reduce. At the same time, the decreased air temperature in 500 hPa would caused the upper troposphere geopotential height to reduce, resulting in high–altitude jet southerly location, the East Asian summer monsoon to weaken, then it was difficult for water vapor transport to cross the Yangtze River valley and reach the North China region, with a southerly summer monsoon rainfall zone. The summer precipitation reduction in North China had a good correlation with the northern hemispheric circulation changes.
基金supported by the Open Research Fund of TPESER(Grant No.TPESER202205)the Second Tibetan Plateau Scientific Expedition and Research Program(Grant No.2019QZKK0101)。
文摘The spring atmospheric heat source(AHS)over the Tibetan Plateau(TP)has been suggested to affect the Asian summer monsoon and summer precipitation over South China.However,its influence on the summer precipitation in Northeast China(NEC)remains unknown.The connection between spring TP AHS and subsequent summer precipitation over NEC from 1961 to 2020 is analyzed in this study.Results illustrate that stronger spring TP AHS can enhance subsequent summer NEC precipitation,and higher soil moisture in the Yellow River Valley-North China region(YRVNC)acts as a bridge.During spring,the strong TP AHS could strengthen the transportation of water vapor to East China and lead to excessive rainfall in the YRVNC.Thus,soil moisture increases,which regulates local thermal conditions by decreasing local surface skin temperature and sensible heat.Owing to the memory of soil moisture,the lower spring sensible heat over the YRVNC can last until mid-summer,decrease the land–sea thermal contrast,and weaken the southerly winds over the East Asia–western Pacific region and convective activities over the South China Sea and tropical western Pacific.This modulates the East Asia–Pacific teleconnection pattern,which leads to a cyclonic anomaly and excessive summer precipitation over NEC.
基金Supported by the National Key Research and Development Program of China(2018YFA0606301)National Natural Science Foundation of China(41875093,41705074,and 41530531).
文摘Sea surface temperature anomaly(SSTA)is a major signal for prediction of summer precipitation in East Asia.The relationship between SSTA in the tropical oceans and summer precipitation in East Asia has been documented in many studies.However,the relationship between SSTA and late summer(July–August)precipitation(JAP)over Northeast China(NEC)on the interannual timescale has received little attention.In this study,we examine the relationship between Indian Ocean Basin warming(IOBW)anomalies in spring and the JAP in NEC since the early1960 s.A significant positive correlation is found between the spring IOBW index and JAP over NEC.The positive spring IOBW anomaly is followed by an anomalous anticyclone from Northwest Pacific to the Korean Peninsula.This anomalous anticyclone favors a significantly strong and northward western Pacific subtropical high(WPSH),which facilitates anomalous southerly winds over NEC and the transport of more water vapor into this region.Further analysis indicates that the spring IOBW anomalies have important impacts on the vertical air motion in the tropics and subtropics during the summer.Significant anomalous upward(downward)motion covering Indonesia(Northwest Pacific to the southern Korean Peninsula)occurs when the IOBW is in its positive phase,which favors the northward movement of the WPSH in late summer and more precipitation over NEC in July–August.Modulation of the atmospheric circulation by this mechanism further influences the JAP over NEC.
基金Supported by the National Natural Science Foundation of China(41330425)China Meteorological Administration Special Public Welfare Research Fund(GYHY201406024)
文摘The variations of regional mean daily precipitation extreme (RMDPE) events in central China and associated circulation anomalies during June, July, and August (JJA) of 1961-2010 are investigated by using daily in-situ precipitation observations and the NCEP/NCAR reanalysis data. The precipitation data were collected at 239 state-level stations distributed throughout the provinces of Henan, Hubei, and Hunan. During 1961-2010, the 99th percentile threshold for RMDPE is 23.585 mm day-1. The number of RMDPE events varies on both interannual and interdecadal timescales, and increases significantly after the mid 1980s. The RMDPE events happen most frequently between late June and mid July, and are generally associated with anomalous baroclinic tropospheric circulations. The supply of moisture to the southern part of central China comes in a stepping way from the outer-region of an abnormal anticyclone over the Bay of Bengal and the South China Sea. Fluxes of wave activity generated over the northeastern Tibetan Plateau converge over central China, which favors the genesis and maintenance of wave disturbances over the region. RMDPE events typically occur in tandem with a strong heating gradient formed by net heating in central China and the large-scale net cooling in the surrounding area. The occurrence of RMDPE events over central China is tied to anomalous local cyclonic circulations, topographic forcing over the northeast Tibetan Plateau, and anomalous gradients of diabatic heating between central China and the surrounding areas.
文摘为改进华北夏季降水异常的预测能力、寻找前期异常信号的监测预测指标,本文利用1961-2020年华北、华南夏季降水资料,美国环境预报中心和大气科学研究中心(National Centers for Environmental Prediction/National Center for Atmospheric Research,NCEP/NCAR)的再分析环流资料、向外长波辐射资料(Outgoing Longwave Radiation,OLR),采用相关、合成和环流异常回归重构等方法,分析了华南前汛期(5-6月)降水异常与华北夏季(7-8月)降水异常的联系。结果表明:(1)华北夏季(7-8月)降水异常通常与华南前汛期(5-6月)降水异常呈反位相关系,即如果华南前汛期降水偏多,对应华北夏季降水就会偏少,反之亦然。华南前汛期降水异常可以作为华北夏季降水异常监测预测的一个前期指标。东亚夏季风造成对流层低层水汽输送异常和北半球夏季热带低频信号传播造成对流层中低层环流异常是两地降水呈反位相变化的联系机制。(2)在水汽输送方面,如果5-6月东亚副热带夏季风偏强,即东亚西南南风(SSW)显著偏强,华南水汽来源会偏少,造成华南前汛期(5-6月)降水异常偏少。到7-8月,印度夏季风显著偏强、东亚副热带夏季风进一步增强,华北水汽来源显著偏多,造成华北夏季(7-8月)降水异常偏多。反之,华南前汛期(5-6月)降水异常偏多,华北夏季(7-8月)降水异常偏少。(3)在动力环流方面,如果5-6月,热带印度洋低频信号活跃、西北太平洋低频信号不活跃,伴随印度洋低频信号向东北方向传播,在850 hPa层华南沿海附近形成反气旋性环流异常,对流减弱,造成华南前汛期(5-6月)降水偏少。到7-8月,热带印度洋低频信号仍然十分活跃,原来位于华南沿海的反气旋性环流异常向东北方向传播到长江下游至东部海上,反气旋北侧的华北地区为气旋性环流,对流偏强;另一方面,伴随低频扰动在对流层中高层向高纬传播,会形成沿高空西风急流传播的扰动波列,扰动位置相对固定,在贝加尔湖附近为负距平、朝鲜半岛附近为正距平,造成贝加尔湖高空槽加深、副热带高压在朝鲜半岛附近加强,形成“东高西低”的阻挡形势,有利于华北产生上升运动。即华北夏季对流上升运动增强,造成华北夏季(7-8月)降水偏多。反之,华南前汛期(5-6月)降水偏多,华北夏季(7-8月)降水偏少。(4)华南前汛期降水异常对华北夏季降水异常有很好的指示意义。但在有些年份关系并不好,这可能是因为这种关系还受到其他因子如海温变化、热带环流、青藏高原以及中高纬环流变化的调节与影响。