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1.
用60 a Hadley气候中心的月平均海温资料,用EOF分析重构了4月份印度洋海温的一致变化型异常,并以此驱动IAP9层大气环流模式,分别研究了海温异常初期适应阶段、异常当月和气候平均夏季3种时间尺度下大气高度场响应的传播和分布特征.研究发现,初期适应阶段,高度场响应的垂直传播约需4d,且受控于整层无辐散约束;冷暖位相高度响应的水平传播路径差异较大,表现出明显的非对称性.海温异常当月,冷位相会激发出全球纬向Rossby波;而暖位相则激发出两半球洋面上2个大圆波列,且均有显著正压性.对气候平均夏季的北半球冷相位,高度响应表现为太平洋上空的3条异常纬带;对暖相位则表现为太平洋和大西洋上空的2个大圆波列.而南半球的高度场对冷位相响应主要表现为2波结构的绕极驻波,暖相位激发出环球的同心异常纬带. 相似文献
2.
北太平洋中纬度负海温异常对副热带高压影响的数值试验 总被引：3，自引：2，他引：3
利用中国科学院大气物理研究所的T42L9全球大气环流模式，研究了1993年夏季北太平洋中纬度海温异常对西太平洋副热带高压的影响。数值试验结果表明：（1）中纬度地区负距平海温异常对其南侧太平洋副热带高压的形态和脊线位置都有影响，负距平海温异常试验的500hPa副热带高压的形态明显比气候平均海温试验更接近于NCEP资料实况，对流层中下层副热带高压脊线的平均位置也比气候平均海温试验要偏南，与实况比也更接近了；（2）在500hPa上，北太平洋中纬度负距平海温异常在其南侧产生的高度扰动使副热带高压向南偏移，而在其北侧产生的高度扰动则沿北太平洋中高纬度、北美中高纬度、北大西洋和欧洲南部以及地中海和北非地区的大圆路径传播，并影响和改变整个北半球大气环流的变化。1993年夏季北太平洋中纬度异常的低海温可能是该年盛夏6、7月北太平洋副热带高压位置异常偏南的重要原因之一。 相似文献
3.
利用欧洲中期天气预报中心ECMWF(European Center for Medium-range Weather Forecast)逐日再分析资料(ERA40),通过经验正交函数(empirical orthogonal function,EOF)分解发现,冬季北太平洋东部风暴轴有着显著的年际变化特征:第一变化模态为在气候平均位置南北相反的偶极子变化型,第二变化模态为在气候平均位置处一致增强或减弱的变化型,第三变化模态为三极子的变化型。进一步的回归分析发现:当东部风暴轴南压(北抬)时,同期冬季是一种厄尔尼诺(拉尼娜)年海温异常空间分布型,中纬度北太平洋海区以及赤道中、东海区,冬季冷(暖)异常的洋面上是异常低压(高压),对流层中层是太平洋—北美型(Pacific-North American Pattern,PNA)遥相关的正(负)位相;当东部风暴轴增强(减弱)时,同期冬季黑潮区海温偏暖(偏冷),对流层中层表现为西太平洋型(West Pacific Pattern,WP)遥相关的正(负)位相;当东部风暴轴呈现西北—东南+-+(-+-)相间三极子的分布时,同期冬季巴布亚新几内亚附近海温异常偏暖(冷),夏威夷附近海温异常偏冷(暖),冬季冷(暖)异常的洋面上是异常低(高)压,对流层中层表现出类似PNA正(负)位相。EOF分解各模态所对应时间系数与阿留申低压(Aleutian Low,AL)指数、PNA指数、Nino3指数、WP指数、黑潮海温(Kuroshio Current,KC)指数之间存在显著的相关,这些证明了东部风暴轴与同期大气环流及SST异常之间的联系。 相似文献
4.
太平洋年代际振荡冷、暖背景下ENSO循环的特征 总被引：12，自引：1，他引：11
利用英国气象局哈德莱中心的月平均海温距平资料、美国Scripps海洋研究所联合环境分析中心(JEDAC)的海表和次表层海温观测资料以及NCEP/NCAR再分析资料,研究了太平洋年代际振荡(PDO)不同背景下ENSO循环的特征.结果表明,PDO为ENSO循环提供了一个年代际气候背景,在PDO的暖位相时期,El Nino事件发生的频率较高,强度较强;反之,在PDO的冷位相时期,La Nina事件发生的频率较高,强度较强.而且在不同的太平洋年代际振荡背景下,ENSO循环表现出不同的特征.在PDO冷位相时期,发生El Nino(La Nina)事件时,正(负)的SOTA从西太平洋沿温跃层向东传播,正(负)的SSTA从赤道东太平洋向西扩展到中太平洋,ENSO事件先在赤道东太平洋爆发.在PDO的暖位相时期,发生El Nino(La Nina)事件时,正(负)的SOTA首先出现在赤道中太平洋,然后沿温跃层向东传播,正(负)的SSTA从赤道中太平洋向东扩展到东太平洋,ENSO事件首先在中太平洋爆发.这为ENSO预测提供了新的线索. 相似文献
5.
我国华南3月份降水年代际变化的特征 总被引：5，自引：2，他引：3
利用1951～2005年华南3月份降水资料、太平洋年代际振荡(PDO)指数以及NCEP再分析资料,对华南3月份降水年代际变化特征、及其对应的大尺度环流以及与PDO的关系进行了分析。结果表明,华南3月份降水存在显著的年代际变化特征,并且Mann-Kendal突变检验表明华南3月份降水在1978年左右发生年代际突变,从之前的降水偏少转变为降水偏多。我国华南3月份降水与PDO有着显著的相关。进一步研究表明,在年代际降水偏少时期,PDO处于负位相(北太平洋海温偏高,中东太平洋海温偏低),北太平洋海平面气压场和高度场偏高,亚洲大陆海平面气压场和高度场偏低,赤道西太平洋到赤道东印度洋附近的海平面气压场偏低,赤道辐合带附近地区的高度场偏低,东亚对流层大气偏暖,西太平洋副热带高压偏东,东亚高空急流偏北,东亚Hadley环流偏弱。在年代际降水偏多时期,PDO处于正位相,情况则与降水偏少时期相反。 相似文献
6.
利用1961—2013年NCEP/NCAR再分析资料和Had ISST月平均海表面温度资料,分析了夏半年热带太平洋中部型海温异常与热带印度洋海盆模(Indian Ocean Basin M ode,IOBM)的特征,并研究了不同位相配置时二者对同期中国东部气候的共同影响。结果表明:1)太平洋中部型海温异常指数与印度洋海盆模指数几乎相互独立。太平洋中部型海温异常与IOBM同位相变化(记为PPNN事件)和反位相变化(记为PNNP事件)时,热带印太地区海温异常分别呈三级型和偶极型分布。2)不同位相配置对中国东部地区降水异常的影响及其影响机制存在显著差异:当发生PPNN事件时,水汽从海洋性大陆(Maritime Continent,MC)地区向江淮流域输送;热带海温异常引起大气产生Gill型响应,维持了中国东部的环流异常;M C地区通过经向三圈异常垂直环流引起江淮流域降水异常增多。发生PNNP事件时,Gill型环流响应中心西移,长江流域降水偏少,水汽辐散;同时MC地区对流层低层准定常Rossby波能传播也有利于长江流域扰动的维持。这些结果对深刻认识中国东部地区夏半年降水异常成因和印度洋/太平洋海温异常不同分布的作用具有重要意义。 相似文献
7.
利用1948—2010年NCEP/NCAR逐月位势高度再分析资料、美国国家海洋局提供的1948—2010年逐月海温再分析资料,分别定义了1 000—500 hPa和500—200 hPa厚度,利用EOF、SVD等方法研究了北半球对流层厚度时空演变特征及其与大气环流和海面温度的关系。结果表明,冬季平均厚度EOF第一模态均具有北太平洋及附近高纬度亚洲大陆地区与北美大陆高纬地区反位相变化的特点,而夏季第一模态则是北半球范围内较一致的位相分布;冬、夏季平均厚度EOF第二模态均突出体现了欧亚大陆及附近地区与北半球其他地区反位相变化的特点;冬、夏季厚度场的变化形势与大气环流及海面温度具有密切联系。 相似文献
8.
利用1951—2008年东北地区夏季平均气温资料,分析了东北地区近58 a来东北地区夏季气温的变化趋势和突变特征,结果表明,东北夏季气温存在明显年代际变化的阶段性特征和总体增暖的趋势。对我国东北夏季气温与太平洋海温的相关分析表明,太平洋年代际振荡(PDO)由冷位相转为暖位相后,我国东北夏季气温与同期赤道中东太平洋海温相关减弱、与黑潮区海温相关增强,我国东北夏季气温与前期各季太平洋海温相关分布差异很大,海温关键区及相关强度都有所改变,这种相关关系的转变可能是造成近几年来利用太平洋海温预测我国东北夏季气温不确定性的原因之一。 相似文献
9.
选用 1 95 1～ 1 996年中国 1 6 0站逐月降水资料 ,太平洋逐月平均网格点海温资料( 1 0°S～ 5 0°N,1 2 0～ 80°E) ,逐月大尺度环流指数资料 ,分析并探讨造成 1 996年南方洪涝的环流特征、气候背景及海温影响机制。结果表明 :大气环流指数与前期太平洋海温场有明显的遥相关关系。冬、春季海温的冷暖变化程度 ,可预示后期 7月各环流系统的趋势变化 ,环流系统指数自身演变存在较明显的年代际变化规律 ,1 996年南方洪涝就是在这种气候背景下形成的。海温冷暖变化影响大气环流系统的这种演变关系 ,对南方洪涝的短期气候预测具有一定的指示意义。 相似文献
10.
（１）利用大气对流层中部无辐散层的存在,垂直积分热力学方程,并对整个对流层的距平加热场作解析近似的描写,联立涡度方程,得到最非绝热地转的２５０ｈＰａ距平流函数方程。它的形式酷似正压涡度方程。（２）讨论了罗斯贝波列的谱平均相速和群速。证明了气候平均高度场的闭合中心,就是中高纬度大气低频振子。其两侧位相变化相反,它的能源主要来自ＣＩＳＫ凝结正反馈或海温的感热。（３）导出了低频相关射线公式,它表明低频射 相似文献
11.
Temporal and Spatial Characteristics of Intraseasonal Oscillations in the Meridional Wind Field over the Subtropical Northern Pacific 总被引：1，自引：0，他引：1 
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下载免费PDF全文 Based on the NCEP/NCAR reanalysis I daily data from 1958 to 2002, climatic characteristics of the 30-60-day intraseasonal oscillations (ISOs) of the zonal wind (u), meridional wind (v), and geopotential height (h) over global areas and especially the ISO of v over the subtropical northern Pacific are analyzed using the space-time spectrum analysis and wavelet transform methods. The results show that the ISO of v is very different from those of u and h, with the former representing the meridional low-frequency disturbances, which are the most active in the subtropics and mid-high latitudes, but very weak in the tropics. In the subtropical Northern Hemisphere, the energies of the ISOs of u and h are both concentrated on the waves with wave number of 1 and periods of 30-60 days, while the main energy of the ISO of v is concentrated on the waves with wave numbers of 4-6 and periods of 30-60 and 70-90 days. The westward propagating energies for the 30-60-day oscillations of u, v, and h are all stronger than the eastward propagating energies in the subtropics. In addition, the ISO of v is the strongest (weakest) in summer (winter) over the subtropics of East Asia and northwestern Pacific, while the situation is reversed over the subtropical northeastern Pacific, revealing a "seesaw" of the ISO intensity with seasons over the subtropics from the northwestern to northeastern Pacific. In the subtropical northwestern Pacific, the interannual and interdecadal changes of the ISO for v at 850 hPa indicate that its activities are significantly strong during 1958 1975, while obviously weak during 1976-1990, and are the strongest during 1991-2000, and its spectral energy is obviously abnormal but ruleless during the ENSO periods. However, in the 2 7-yr bandpass filtering series, the interannual changes of the v ISO over the subtropical northwestern Pacific contain distinct ENSO signals. And in the 9-yr low-pass filtering series, the v ISO changes over the subtropical northwestern Pacific are significantly out of phase with the changes of the Ni(n)o -3.4 SST, whereas the v ISO changes in the subtropical northeastern Pacific are significantly in phase with the changes of the Ni(n)o-3.4 SST. 相似文献
12.
本文利用1951—1980年逐季的平均值资料(共120个季)讨论了北方涛动和与其相联系的北太平洋海温与北半球海平面气压场、500hPa位势高度场遥相关的基本结构,并与南方涛动和赤道东太平洋海温的结果进行了对比分析.发现北太平洋Namias海区和加利福尼亚海流区海温的变化与北方涛动具有很密切的联系;北方涛动和这两个海区的海温同北半球中高纬度大气环流特别是PNA型和NAO型环流异常存在明显的遥相关关系;南方涛动和赤道太平洋海温同WP型或NPO型环流异常关系比较密切,而与PNA型和NAO型的关系不如北方涛动和Namias海区及加利福尼亚海流区海温的显著. 相似文献
13.
A NUMERICAL STUDY OF SHORT-RANGE CLIMATIC OSCILLATION WITH VARIOUS TIME SCALES FORCED BY EL NINO DURING THE NORTHERN SUMMER 下载免费PDF全文
下载免费PDF全文 The normal mode method is adopted to decompose the differences between simulations with SST(seasurface temperature)anomahes over centra-eastern Pacific and normal SST by use of a nine-layer global spec-tral model in order to investigate short-range climatic oscillation with various time scales forced by ElNino during the northern summer.Investigation shows that El Nino may have the following influence onatmosphere on various space-time scales.Extra-long wave components of Rossby mode forced by convectiveanomaly over equatorial western Pacific resulting from El Nino produce climatic oscillation on monthly(sea-sonal)time scale in middle-high latitudes of Southern and Northern Hemispheres;extra-long wave componentsof Kelvin mode forced by SST anomalies propagate along the equator,resulting in 30—60 day oscillation oftropical and subtropical atmosphere;and its long waves move eastward with westerly,resulting in quasi-biweekoscillation. 相似文献
14.
东亚夏季风的年际到年代际变化及其与全球大气环流和海表温度的联系 总被引：23，自引：1，他引：23
The East Asian summer monsoon (EASM) underwent an interdecadal variation with interannual variations during the period from 1958 to 1997, its index tended to decline from a higher stage in the mid-1960＇s until it reached a lower stage after 1980＇s. Correlation analysis reveals that EASM is closely related with the global atmospheric circulation and sea surface temperature (SST). The differences between the weak and strong stage of EASM shows that, the summer monsoon circulation over East Asia and North Africa is sharply weakened, in the meantime, the westerlies in high latitudes and the trade--wind over the tropical ocean are also changed significantly. Over the most regions south of the northern subtropics, both air temperature in the lower troposphere and SST tended to rise compared with the strong stage of EASM. It is also revealed that the ocean-atmosphere interaction over the western Pacific and Indian Ocean plays a key role in interannual to interdecadal variation of EASM, most probably, the subtropical Indian Ocean is more important. On the other hand, the ENSO event is less related to EASM at least during the concerned period. 相似文献
15.
本文利用中国近五百年旱涝等级资料，用典型相关的方法重建了15世纪以来的南方涛动指数（SOI）和北太平洋海温（SST）场。在SOI的重建中校准了1913—1973年校准期方差的40%，在1852—1912年的独立验证期验证了方差的20%；在北太平洋SST的重建中校准的方差较高，其中赤道东太平洋SST的校准方差达60%，在近100年的定性检验中效果也很好。说明用中国历史时期的旱涝资料能够在一定程度上重建出历史时期的ENSO事件。通过对15世纪以来SO和SST重建值的分析发现，ENSO事件不但具有明显的周期性，而且还有250年左右的阶段性变化。SO和SST不仅存在2—7年公认的周期，而且历史上SO还有10.6年、赤道东太平洋SST还有25—28.5年及100年左右与太阳活动有关的周期、进一步分析还得出，18，19世纪及20世纪前期SO低指数事件发生相对较少，15世纪后期、16、17世纪及20世纪后期SO低指数事件发生较多；且历史上的低指数多发期与气候上的冷期一致，而低指数少发期则与气候上的暖期一致；气候上的干旱（湿润）期则与东太平洋长期偏冷（暖）、西太平洋长期偏暖（冷）相对应。 相似文献
16.
Prediction of the Pacific sea surface temperature (SST) anomaly in the coming decades is a challenge as the SST anomaly changes over time due to natural and anthropogenic climate forcing. The climate changes in the mid-1970s and late-1990s were related to the decadal Pacific SST variability. The changes in the mid-1970s were associated with the positive phase of decadal El Niño-Southern Oscillation (ENSO)-like SST variation, and the changes in the late-1990s were related to its negative phase. However, it is not clear whether this decadal SST variability is related to any external forcing. Here, we show that the effective solar radiation (ESR), which includes the net solar radiation and the effects of volcanic eruption, has modulated this decadal ENSO-like oscillation. The eastern Pacific warming (cooling) associated with this decadal ENSO-like oscillation over the past 139 years is significantly related to weak (strong) ESR. The weak ESR with strong volcanic eruption is found to strengthen the El Niño, resulting in an El Niño-like SST anomaly on the decadal time scale. The strong eruptions of the El Chicho’n (1982) and Pinatubo (1991) volcanoes reduced the ESR during the 1980s and 1990s, respectively. The radiation reduction weakened the Walker circulation due to the “ocean thermostat” mechanism that generates eastern Pacific warming associated with a decadal El Niño-like SST anomaly. This mechanism has been confirmed by the millennium run of ECHO-G model, in which the positive eastward gradient of SST over the equatorial Pacific was simulated under the weak ESR forcing on the decadal time scale. We now experience a reversal of the trend in the ESR. The strong solar radiation and lack of strong volcanic eruptions over the past 15 years have resulted in strong ESR, which should enhance the Walker circulation, leading to a La Niña-like SST anomaly. 相似文献
17.
新疆北部雨季降水对ENSO的响应 总被引：1，自引：0，他引：1
分析研究了新疆北部地区近50年（1951－2000年）全年各月降水的气候分布特征和各季降水的年际变化规律，重点揭示了北疆多雨季节（4－7月）及各月降水量对赤道东太平洋的海温SST和南方涛动指数SOI的显著响应关系，并用前期SST和SOI作为预报因子，建立了北疆地区雨季降水量的预报方程，该方程对北疆地区雨季降水量的长期预报有重要的应用价值。 相似文献
18.
Large-Scale Temperature Changes across the Southern Andes: 20th-Century Variations in the Context of the Past 400 Years 总被引：4，自引：0，他引：4
Ricardo Villalba Antonio Lara José A. Boninsegna Mariano Masiokas Silvia Delgado Juan C. Aravena Fidel A. Roig Andrea Schmelter Alexia Wolodarsky Alberto Ripalta 《Climatic change》2003,59(1-2):177-232
Long-term trends of temperature variations across the southern Andes (37–55° S) are examined using a combination of instrumental and tree-ring records. A critical appraisal of surface air temperature from station records is presented for southern South America during the 20th century. For the interval 1930–1990, three major patterns in temperature trends are identified. Stations along the Pacific coast between 37 and 43° S are characterized by negative trends in mean annual temperature with a marked cooling period from 1950 to the mid-1970s. A clear warming trend is observed in the southern stations (south of 46°S), which intensifies at higher latitudes. No temperature trends are detected for the stations on the Atlantic coast north of 45° S. In contrast to higher latitudes in the Northern Hemisphere where annual changes in temperature are dominated by winter trends, both positive and negative trends in southern South America are due to mostly changes in summer (December to February) temperatures. Changes in the Pacific Decadal Oscillation (PDO) around 1976 are felt in summer temperatures at most stations in the Pacific domain, starting a period with increased temperature across the southern Andes and at higher latitudes.Tree-ring records from upper-treeline were used to reconstruct past temperature fluctuations for the two dominant patterns over the southern Andes. These reconstructions extend back to 1640 and are based on composite tree-ring chronologies that were processed to retain as much low-frequency variance as possible. The resulting reconstructions for the northern and southern sectors of the southern Andes explain 55% and 45% ofthe temperature variance over the interval 1930–1989, respectively. Cross-spectral analysis of actual and reconstructed temperatures over the common interval 1930–1989, indicates that most of the explained varianceis at periods >10 years in length. At periods >15 years, the squaredcoherency between actual and reconstructed temperatures ranges between 0.6 and 0.95 for both reconstructions. Consequently, these reconstructions are especially useful for studying multi-decennial temperature variations in the South American sector of the Southern Hemisphere over the past 360 years. As a result, it is possible to show that the temperatures during the 20thcentury have been anomalously warm across the southern Andes. The mean annual temperatures for the northern and southern sectors during the interval 1900–1990 are 0.53 °C and 0.86 °C above the1640–1899 means, respectively. These findings placed the current warming in a longer historical perspective, and add new support for the existence of unprecedented 20th century warming over much of the globe. The rate of temperature increase from 1850 to 1920 was the highest over the past 360 years, a common feature observed in several proxy records from higher latitudes in the Northern Hemisphere.Local temperature regimes are affected by changes in planetary circulation, with in turn are linked to global sea surface temperature (SST) anomalies. Therefore, we explored how temperature variations in the southern Andes since 1856 are related to large-scale SSTs on the South Pacific and South Atlantic Oceans. Spatial correlation patterns between the reconstructions and SSTs show that temperature variations in the northern sector of the southern Andes are strongly connected with SST anomalies in the tropical and subtropical Pacific. This spatial correlation pattern resembles the spatial signature of the PDO mode of SST variability over the South Pacific and is connected with the Pacific-South American (PSA) atmospheric pattern in the Southern Hemisphere. In contrast, temperature variations in the southern sector of the southern Andes are significantly correlated with SST anomalies over most of the South Atlantic, and in less degree, over the subtropical Pacific. This spatial correlation field regressed against SST resembles the `Global Warming' mode of SST variability, which in turn, is linked to the leading mode of circulation in the Southern Hemisphere. Certainly, part of the temperature signal present in the reconstructions can be expressed as a linear combination of four orthogonal modes of SST variability. Rotated empirical orthogonal function analysis, performed on SST across the South Pacific and South Atlantic Oceans, indicate that four discrete modes of SST variability explain a third, approximately, of total variance in temperature fluctuations across the southern Andes. 相似文献
19.
Decadal-scale climate variability in the tropical and North Pacific during the 1970s and 1980s: observations and model results 总被引：32，自引：3，他引：32
N E Graham 《Climate Dynamics》1994,10(3):135-162
An abrupt change in the large-scale boreal winter circulation pattern over the North Pacific was observed during the mid-1970s. Most notably, this change was marked by a southward shift and intensification of the Aleutian Low and prevailing westerlies over the mid-latitude central and eastern Pacific. Associated changes in diverse North Pacific climatological, hydrological, and biological variables have been noted by numerous researchers. Intriguingly, the timing of these changes in the extra-tropical circulation was coincident with a shift in the background state of the coupled ocean-atmosphere system over the tropical Pacific. These changes include increases in SST over broad regions of the central and eastern tropical Pacific and an eastward displacement of the region of persistent convection in the western Pacific. This paper presents a variety of observed data and model results to describe the climate shift, and to understand some of the links within the coupled climate system that produced it. Five main findings are emphasized: (1) evidence of abrupt, simultaneous, and apparently related changes can be found in many fields and in many model results; the climate shift is not an artifact, (2) over the tropical Pacific the climate change represents a shift in the state of the coupled ocean-atmosphere system, some aspects of which resemble features associated with El Niño episodes. However, the shift in state is not well characterized as due to a change in the frequency of intensity of El Ni~no episodes; it is better described as a change in background mean state, (3) when forced with observed SSTs, both a very simple atmospheric model and a full general circulation model (GCM) qualitatively simulate aspects of the decadal-scale shift over the tropical Pacific, (4) when forced with observed surface wind stress, two ocean models of the tropical Pacific, in which surface heat fluxes are parameterized as Newtonian damping, reproduce some aspects of the near-equatorial decadal SST signal. However, the models do not reproduce the large changes in SST observed at higher latitudes of the tropical Pacific, suggesting that altered surface heat fluxes dominated in producing these changes, and (5) an important new finding of this study is the success of a GCM in reproducing important aspects of the observed mid-1970s shift in winter northern hemisphere circulation. Comparative analyses of the observed and GCM simulated circulation suggest the altered patterns of tropical Pacific SST and convection were important in forcing the changes in the mid-latitude circulation, a finding corroborated by recent GCM experiments. 相似文献
20.
June-Yi Lee MinHo Kwon Kyung-Sook Yun Seung-Ki Min In-Hong Park Yoo-Geun Ham Emilia Kyung Jin Joo-Hong Kim Kyong-Hwan Seo WonMoo Kim So-Young Yim Jin-Ho Yoon 《Asia-Pacific Journal of Atmospheric Sciences》2017,53(2):257-272
Changma, which is a vital part of East Asian summer monsoon (EASM) system, plays a critical role in modulating water and energy cycles in Korea. Better understanding of its long-term variability and change is therefore a matter of scientific and societal importance. It has been indicated that characteristics of Changma have undergone significant interdecadal changes in association with the mid-1970s global-scale climate shift and the mid-1990s EASM shift. This paper reviews and revisits the characteristics on the long-term changes of Changma focusing on the underlying mechanisms for the changes. The four important features are manifested mainly during the last few decades: 1) mean and extreme rainfalls during Changma period from June to September have been increased with the amplification of diurnal cycle of rainfall, 2) the dry spell between the first and second rainy periods has become shorter, 3) the rainfall amount as well as the number of rainy days during August have significantly increased, probably due to the increase in typhoon landfalls, and 4) the relationship between the Changma rainfall and Western Pacific Subtropical High on interannual time scale has been enhanced. The typhoon contribution to the increase in heavy rainfall is attributable to enhanced interaction between typhoons and midlatitude baroclinic environment. It is noted that the change in the relationship between Changma and the tropical sea surface temperature (SST) over the Indian, Pacific, and Atlantic Oceans is a key factor in the long-term changes of Changma and EASM. Possible sources for the recent mid-1990s change include 1) the tropical dipole-like SST pattern between the central Pacific and Indo-Pacific region (the global warming hiatus pattern), 2) the recent intensification of tropical SST gradients among the Indian Ocean, the western Pacific, and the eastern Pacific, and 3) the tropical Atlantic SST warming. 相似文献