This study unveils the evolution of two major early signals in the North Pacific atmosphere-ocean system that heralded abnormal high-pressure blockings and cold-vortex activities across Northeast China, based on an an...This study unveils the evolution of two major early signals in the North Pacific atmosphere-ocean system that heralded abnormal high-pressure blockings and cold-vortex activities across Northeast China, based on an analysis of the configurations of major modes including the polar vortex, the North Pacific Oscillation （NPO）, and SST in the preceding winter and spring and atmospheric low-frequency disturbances in Northeast China. We analyzed these aspects to understand the atmosphere ocean physical coupling processes characterized by the two early signals, and here we explain the possible mechanisms through which dipole circulation anomalies affect the summer low-temperature processes in Northeast China. We further analyzed the interdecadal variation background and associated physical processes of the two early signals.展开更多
The linkage between the Asian-Pacific oscillation （APO） and the precipitation over central eastern China in spring is preliminarily addressed by use of the observed data. Results show that they correlate very well, ...The linkage between the Asian-Pacific oscillation （APO） and the precipitation over central eastern China in spring is preliminarily addressed by use of the observed data. Results show that they correlate very well, with the positive （negative） phase of APO tending to increase （decrease） the precipitation over central eastern China. Such a relationship can be explained by the atmospheric circulation changes over Asia and the North Pacific in association with the anomalous APO. A positive phase of APO, characterized by a positive anomaly over Asia and a negative anomaly over the North Pacific in the upper-tropospheric temperature, corresponds to decreased low-level geopotential height （H） and increased high-level H over Asia, and these effects are concurrent with increased low-level H and decreased high-level H over the North Pacific. Meanwhile, an anticyclonic circulation anomaly in the upper troposphere and a cyclonic circulation anomaly in the lower troposphere are introduced in East Asia, and the low-level southerly wind is strengthened over central eastern China. These changes provide advantageous conditions for enhanced precipitation over central eastern China. The situation is reversed in the negative phase of APO, leading to reduced precipitation in this region.展开更多
Under the background of global warming, summer （JJA） low temperature events in Northeast China had not occurred for about 15 yr since 1994, but one such event took place in 2009. By using the NCEP/NCAR reanalysis da...Under the background of global warming, summer （JJA） low temperature events in Northeast China had not occurred for about 15 yr since 1994, but one such event took place in 2009. By using the NCEP/NCAR reanalysis data, the 100-yr station temperature data at Harbin and Changchun, and the Hadley Center sea surface temperature （SST） data, this paper intends to reveal the cause, circulation background, and influencing factors of this event. Analysis of both horizontal and vertical circulations of a low-value system over Northeast China in summer 2009 during the low temperature event shows that anomalous activities of the Northeast China cold vortex （NECV） played the most direct role. A decadal cooling trend of - 0.8℃ （10 yr）-1 over 1999-2008 at Changchun and Harbin was found, which is obviously out-of-phase with the linear warming trend （0.2℃ （10 yr）-1） over 1961-2000 for Northeast China in response to the global warming. The previous winter North Pacific polar vortex （NPPV） area index, significantly positively related to the observed summer temperatures of Harbin and Changchun, was also in a significantly declining tendency. These provide favorable decadal backgrounds for the 2009 low temperature event. Different from the average anomaly field of 500-hPa height for summer 1994-2008 in Northeast China, in the summer of 2009, the Arctic Oscillation （AO） showed a strong negative phase distribution, and significant negative height anomalies dominated Northeast Asia, Aleutian Islands, and North Atlantic. Furthermore, the negative phase of North Pacific Oscillation （NPO） in the winter of 2008 was obviously strong, and it maintained in the spring of 2009. Meanwhile, the SSTA in the equatorial eastern-central Pacific Ocean in the winter of 2008 showed a La Nina phase, but the strength of the La Nina weakened obviously in the spring of 2009. The abnormally strong activities of NECV in June and July of 2009 were related to the disturbances of stationary waves that replaced the original ultra-long waves over the North Pacific region in April and May 2009. The singular value decomposition （SVD） and harmonic analysis results suggest that the anomalous phase of NPO is an important precursor for summer temperature variations over Northeast China, and also a stable planetary-scale component that can be extracted from the atmospheric circulation in addition to the chaotic components on the synoptic scale.展开更多
明末清初中国社会动荡加剧,王朝更迭,伴随着华北地区较为明显的年代际气候变化。本研究使用CESM-LME(CESM Last Millennium Ensemble)模拟数据,结合重建证据,对明末清初华北夏季降水年代际气候变化特征和原因进行了分析。重建证据显示,1...明末清初中国社会动荡加剧,王朝更迭,伴随着华北地区较为明显的年代际气候变化。本研究使用CESM-LME(CESM Last Millennium Ensemble)模拟数据,结合重建证据,对明末清初华北夏季降水年代际气候变化特征和原因进行了分析。重建证据显示,1644年华北夏季降水发生由少到多的年代际转变,中国东部夏季降水呈“南旱北涝”的变化格局。CESM-LME集合试验成员012能够模拟出这样的年代际转变,但模拟的变化幅度偏弱且转变发生时间略晚。模拟显示,北太平洋出现类PDO(Pacific Decadal Oscillation,太平洋年代际振荡)正位相的海温年代际异常,引起日本海附近低压异常。同时,热带太平洋呈现类拉尼娜型海温异常,使得菲律宾以东洋面对流增强、降水增加,通过北传罗斯贝波激发类东亚-太平洋遥相关,导致西北太平洋副热带高压增强西伸和日本海附近异常低压的加强。对应于这样的环流异常,华北有北风异常,长江以南有南风异常,华北地区南部水汽辐合增强,有异常的上升运动,华北夏季降水年代际增多,并伴随着东亚副热带西风急流的向南移动。伴随华北夏季降水年代际转变,华北土地承载力提高,社会系统逐渐恢复和稳定。展开更多
基金supported by the National Natural Science Foundation of China (Grant Nos. 41175083 and 41275096)the Special Fund for Meteorological Scientific Research in the Public Interest (Grant Nos. GYHY201006020,GYHY201106016,and GYHY201106015)
文摘This study unveils the evolution of two major early signals in the North Pacific atmosphere-ocean system that heralded abnormal high-pressure blockings and cold-vortex activities across Northeast China, based on an analysis of the configurations of major modes including the polar vortex, the North Pacific Oscillation （NPO）, and SST in the preceding winter and spring and atmospheric low-frequency disturbances in Northeast China. We analyzed these aspects to understand the atmosphere ocean physical coupling processes characterized by the two early signals, and here we explain the possible mechanisms through which dipole circulation anomalies affect the summer low-temperature processes in Northeast China. We further analyzed the interdecadal variation background and associated physical processes of the two early signals.
基金supported by the National Basic Research Program of China (2009CB421407)the Special Fund for Public Welfare Industry(meteorology)(GYHY200906018)the National Natural Science Foundation of China(90711004 and 40921003)
文摘The linkage between the Asian-Pacific oscillation （APO） and the precipitation over central eastern China in spring is preliminarily addressed by use of the observed data. Results show that they correlate very well, with the positive （negative） phase of APO tending to increase （decrease） the precipitation over central eastern China. Such a relationship can be explained by the atmospheric circulation changes over Asia and the North Pacific in association with the anomalous APO. A positive phase of APO, characterized by a positive anomaly over Asia and a negative anomaly over the North Pacific in the upper-tropospheric temperature, corresponds to decreased low-level geopotential height （H） and increased high-level H over Asia, and these effects are concurrent with increased low-level H and decreased high-level H over the North Pacific. Meanwhile, an anticyclonic circulation anomaly in the upper troposphere and a cyclonic circulation anomaly in the lower troposphere are introduced in East Asia, and the low-level southerly wind is strengthened over central eastern China. These changes provide advantageous conditions for enhanced precipitation over central eastern China. The situation is reversed in the negative phase of APO, leading to reduced precipitation in this region.
基金Supported by the National Natural Science Foundation of China(41175083,41275096,and40705036)National Science and Technology Support Program of China(2009BAC51B04 and 2007BAC29B01)China Meteorological Administration Special Public Welfare Research Fund(GYHY 20106020 and 201106016)
文摘Under the background of global warming, summer （JJA） low temperature events in Northeast China had not occurred for about 15 yr since 1994, but one such event took place in 2009. By using the NCEP/NCAR reanalysis data, the 100-yr station temperature data at Harbin and Changchun, and the Hadley Center sea surface temperature （SST） data, this paper intends to reveal the cause, circulation background, and influencing factors of this event. Analysis of both horizontal and vertical circulations of a low-value system over Northeast China in summer 2009 during the low temperature event shows that anomalous activities of the Northeast China cold vortex （NECV） played the most direct role. A decadal cooling trend of - 0.8℃ （10 yr）-1 over 1999-2008 at Changchun and Harbin was found, which is obviously out-of-phase with the linear warming trend （0.2℃ （10 yr）-1） over 1961-2000 for Northeast China in response to the global warming. The previous winter North Pacific polar vortex （NPPV） area index, significantly positively related to the observed summer temperatures of Harbin and Changchun, was also in a significantly declining tendency. These provide favorable decadal backgrounds for the 2009 low temperature event. Different from the average anomaly field of 500-hPa height for summer 1994-2008 in Northeast China, in the summer of 2009, the Arctic Oscillation （AO） showed a strong negative phase distribution, and significant negative height anomalies dominated Northeast Asia, Aleutian Islands, and North Atlantic. Furthermore, the negative phase of North Pacific Oscillation （NPO） in the winter of 2008 was obviously strong, and it maintained in the spring of 2009. Meanwhile, the SSTA in the equatorial eastern-central Pacific Ocean in the winter of 2008 showed a La Nina phase, but the strength of the La Nina weakened obviously in the spring of 2009. The abnormally strong activities of NECV in June and July of 2009 were related to the disturbances of stationary waves that replaced the original ultra-long waves over the North Pacific region in April and May 2009. The singular value decomposition （SVD） and harmonic analysis results suggest that the anomalous phase of NPO is an important precursor for summer temperature variations over Northeast China, and also a stable planetary-scale component that can be extracted from the atmospheric circulation in addition to the chaotic components on the synoptic scale.
