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1.
MJO对我国东部春季降水影响的分析 总被引：12，自引：0，他引：12
利用澳大利亚气象局的MJO(Madden-Julian Oscillation)指数,通过位相合成及对比分析研究了MJO对我国东部春季降水的影响.研究表明,当MJO传播至中东印度洋时,我国长江中下游地区的春季降水为正异常,当其进一步东传至中南半岛-印尼群岛一带时,我国华南地区的春季降水为正异常,而在其他活动阶段不利于我国东部的春季降水.对比分析表明,MJO的活动主要通过引起大尺度环流异常、对流层中低层涡度及水汽输送的异常,进而对我国东部春季降水产生明显的影响. 相似文献
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利用再分析资料分析了MJO（Madden-Julian Oscillation）不同位相对春季中国东部降水的影响。结果表明：MJO处于位相3时对应长江及其以南地区降水增多,处于位相7时该区域降水减小。当热带MJO对流从位相1东传至位相4,与其相伴的北向辐散辐合流会在印度东北部—长江及副热带西北太平洋地区的对流层中低层产生明显的辐合异常,且在MJO位相3时中国东部的辐合异常达到最大。从Rossby波源角度分析,这种辐合异常会增强对流层中低层气旋性环流,导致MJO处于位相3时长江流域及其以南地区降水增多。同时,利用现代次季节和季节预报业务系统探讨了MJO与降水的关系对降水预报技巧的影响,发现预报降水和再分析产品的相关系数在MJO处于位相3和7时有所增加。 相似文献
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POSSIBLE IMPACTS OF MADDEN-JULIAN OSCILLATION ON THE SEVERE RAIN-SNOW WEATHER IN CHINA DURING NOVEMBER 2009 总被引：4，自引：2，他引：2
Possible relationships between MJO and the severe rain-snow weather in Eastern China during November of 2009 are analyzed and results show that a strong MJO process is one of the strong impact factors.MJO is very active over the Indian Ocean in November 2009.Especially,it maintains 9 days in MJO phase 3,just corresponding to the two strongest rain-snow processes.Composites of MJO events show that when the MJO convective center is located over the Indian Ocean,the probability of rainfall is significantly increased and the temperature is lower than normal in eastern China,which is consistent with the situation in November of 2009.Atmospheric circulation anomalies of mid-and higher-latitudes can be influenced by the tropical MJO convection forcing and this influence could be realized by teleconnection.When the MJO is over the Indian Ocean,it is favorable for the maintenance of a circulation pattern of two ridges versus one trough at mid-and higher-latitudes.Meanwhile,the western Pacific subtropical high is stronger and more westward than normal,and a significant convective belt appears over eastern East Asia.All these circulation anomalies shown in the composite result also appeared in the observations in November 2009,which indicates the general features of relationships between the MJO and the circulation anomalies over the extratropics.Besides the zonal circulation anomalies,the MJO convection can also lead to meridional circulation anomalies.When the MJO convection is located over the Indian Ocean,the western Pacific is dominated by anomalous descending motion,and the eastern East Asia is controlled by strong convergence and ascending motion.Therefore,an anomalous meridional circulation is formed between the tropics and middle latitudes,enhancing the northward transportation of low-level moisture.It is potentially helpful to understanding and even forecasting such kind of rain-snow weather anomalies as that in November 2009 using MJO. 相似文献
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Impacts of the MJO on Winter Rainfall and Circulation in China 总被引：10，自引：0，他引：10
Impacts of the MJO on winter rainfall and circulation in China are investigated using a real-time multivariate MJO index.Composite results using the daily rainfall anomalies and "rainy day" anomalies according to eight different MJO phases show that the MJO has considerable influence on winter rainfall in China. Rainfall anomalies show systematic and substantial changes(enhanced/suppressed) in the Yangtze River Basin and South China with the eastward propagation of the MJO convective center from the Indian Ocean to the western Pacific.When the MJO is in phase 2 and 3(MJO convective center is located over the Indian Ocean),rainfall probability is significantly enhanced.While in phase 6 and 7(MJO convective center is over the western Pacific),rainfall probability is significantly reduced. MJO in winter influences the rainfall in China mainly through modulating the circulation in the subtropics and mid-high latitudes.For the subtropics,MJO influences the northward moisture transport coming from the Bay of Bengal and the South China Sea by modulating the southern trough of the Bay of Bengal and the western Pacific subtropical high.For the mid-high latitudes,the propagation of the low frequency perturbations associated with the eastward-propagating MJO convection modulate the circulation in the mid-high latitudes,e.g.the East Asian winter monsoon and the low trough over central Asia. 相似文献
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我国夏季降水与全球气温场的关系 总被引：2，自引：1，他引：2
用蒙特卡罗的相关方法研究我国夏季大尺度降水与全球气温场关系，发现我国夏季大尺度降水与全球气温场有密切相关，以同期相关为最密切；除与热带西太平洋、东太平洋等海域有密切相关外，还与欧洲东部、北美洲东北部以及东亚等内陆地区的不同季节气温场有关系。研究还表明，印度洋地区春季气温和北美洲北部及北太平洋西南部夏季气温偏高时，长江中下游夏季易涝。且它们与长江中下游夏季降水的相关均有阶段性，相关密切程度随时间有所增强。 相似文献
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中国东部夏季降水与东亚垂直环流结构及其预测试验 总被引：2，自引：1，他引：1
本文在分析中国东部夏季降水的时空分布特征基础上, 从东亚高、中、低层大尺度环流异常着手, 选取对中国东部夏季降水异常有显著影响的大气环流预报因子, 分别应用逐步回归和最优子集回归法两种统计降尺度方法, 以动力气候模式CAM3.1预报输出的大气环流预报因子为基础, 以中国东部夏季降水的典型空间分布型为预报对象, 建立动力与统计相结合的中国东部夏季降水预测模型, 并对1981～2000年的中国东部夏季降水进行回报试验。结果表明: 中国东部夏季降水具有4类典型的空间分布型式, 且具有显著的准2年和年代际尺度振荡周期; 东亚高、中、低层大气环流异常的特定配置, 对东部夏季降水的空间分布型有显著影响; 使用两种降尺度方案建立的动力与统计相结合的预测模型对中国东部夏季降水异常具有一定的预报技巧, 可以在一定程度上提高动力模式对中国东部夏季降水的预报效果。 相似文献
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热带印度洋MJO活动对孟加拉湾西南夏季风季节内振荡的影响 总被引：1，自引：0，他引：1
通过对1979—2008年热带太平洋30—60 d振荡(Madden-Julian Oscillation,MJO)指数、美国国家环境预报中心再分析资料和日本气象厅降水资料的分析,发现热带东印度洋MJO强度和传播状况影响孟加拉湾西南夏季风季节内振荡及相关低频环流、对流和降水分布。当热带东印度洋MJO在春末夏初较活跃时,孟加拉湾西南季风季节内振荡活动在4—8月比其不活跃时提前约20 d(约1/2个周期),其对于孟加拉湾西南季风季节内振荡的影响可持续整个季风期,使西南季风的季节内振荡不仅酝酿期和活跃期提前发生,季风期有所延长,季节内振荡也更强。西南季风季节内振荡具有明显的北传和东传特征,北传沿孟加拉湾通道从赤道向副热带推进,而东传则沿10°—20°N从孟加拉湾向东传至南海地区。春末夏初时热带东印度洋MJO的异常状况,正是通过对西南季风季节内振荡东传和北传的影响,进而对孟加拉湾西南季风季节内振荡在季风期的酝酿、维持和活跃产生作用,这种作用同时体现在强度和时间上。孟加拉湾西南夏季风季节内振荡强度与热带东印度洋MJO在4月21日—5月5日的活动呈现显著负相关,当热带东印度洋MJO在春末夏初较活跃时,孟加拉湾西南夏季风季节内振荡的强度较大,在5—8月经历3次季节内振荡波动,低频对流场和环流场在1—3位相(孟加拉湾西南夏季风季节内振荡为正位相)和4—6位相(负位相)时呈反位相特征,这是由MJO低频对流的东传及在孟加拉湾和南海这两个通道上的北传引起的。从印度半岛到菲律宾群岛的降水在1—3位相和4—6位相上分别为正异常和负异常,其中,在第2位相(孟加拉湾西南季风季节内振荡波峰)和第5位相(孟加拉湾西南季风季节内振荡波谷)时分别为降水最大正异常和最大负异常。反之,在热带印度洋MJO在春末夏初不活跃年时,孟加拉湾西南夏季风季节内振荡活动较弱,强度偏弱且振荡也不规律。 相似文献
9.
春夏东亚大气环流年代际转折的影响及其可能机理 总被引：2，自引：0，他引：2
本文通过多变量联合经验正交分解(MV-EOF)方法揭示了近30年(1979~2010年) 春季和夏季东亚大气环流所发生的年代际转折及其与中国南方降水年代际季节反相变化的内在联系,探讨了局地性大气热源年代际变化影响东亚大气环流年代际转折的可能机理.结果表明:(1)东亚大气环流春季第一模态和夏季第二模态在90年代中期都发生了明显的年代际转折;(2)与春季大气环流第一模态和夏季大气环流第二模态年代际转折相对应的是中国南方降水明显的年代际季节反相变化,即春季降水年代际减少,夏季降水年代际增多;(3)春季青藏高原和夏季贝加尔湖地区大气热源年代际变化对东亚大气环流年代际转折有一定贡献,是造成中国南方降水年代际季节反相变化的直接原因;(4)春季青藏高原大气热源的年代际减弱,使得高原东南侧的西南风减弱,导致中国南方上空水汽输送不足,春季降水减少.夏季贝加尔湖大气热源偶极型分布由“南负北正”转变为“南正北负”,由此在贝湖上空激发高压异常,使得夏季雨带北进受阻而停滞南方,造成中国南方夏季降水增多. 相似文献
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Simulation of the Effects of the Preceding SST Anomalies over the Tropical Eastern Pacific on Precipitation to the South of the Yangtze River in June 
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下载免费PDF全文 Numerical experiments are performed to simulate the response of the atmospheric circulation and pre-cipitation over East China in June to the sea surface temperature（SST）anomalies over the tropical eastern Pacific（TEP）from preceding September to June by using an atmospheric general circulation model （AGCM）.We constructed composite positive/negative SST anomalies（P-SSTAs/N-SSTAs）based on the observational SST anomalies over the TEP from September 1997 to June 1998.The results show that：（1） the response of the precipitation in the Yangtze River basin and its southern area（YRBS）to El Nino with different durations varies with the maximum amplitude of the precipitation anomalies appearing when the imposed duration is from November to next June,and the minimum appearing when the SST anomalies is only imposed in June.The anomalies of the precipitation are reduced when the duration of the forcing SST anomalies over the TEP is shortened and the positive SST anomalies in the preceding autumn tend to cause significantly more rainfall in the YRBS.This is in agreement with previous diagnostic analysis results.（2）The simulated precipitation anomalies over the YRBS are always obviously positive under strong or weak positive SST anomalies over the TEP.The intensity of the precipitation anomalies increases with increasing intensity of the SST anomalies in the experiments.The simulation results are consistent with the observations during the warm SST events,suggesting reasonable modeling results.（3）When negative SST anomalies in the TEP are put into the model,the results are different from those of the diagnostic analysis of La Nina events.Negative precipitation anomalies in YRBS could be reproduced only when the negative SST anomalies are strong enough. 相似文献
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Increased evidence has shown the important role of Atlantic sea surface temperature (SST) in modulating the El Niño–Southern Oscillation (ENSO). Persistent anomalies of summer Madden–Julian Oscillation (MJO) act to link the Atlantic SST anomalies (SSTAs) to ENSO. The Atlantic SSTAs are strongly correlated with the persistent anomalies of summer MJO, and possibly affect MJO in two major ways. One is that an anomalous cyclonic (anticyclonic) circulation appears over the tropical Atlantic Ocean associated with positive (negative) SSTA in spring, and it intensifies (weakens) the Walker circulation. Equatorial updraft anomaly then appears over the Indian Ocean and the eastern Pacific Ocean, intensifying MJO activity over these regions. The other involves a high pressure (low pressure) anomaly associated with the North Atlantic SSTA tripole pattern that is transmitted to the mid- and low-latitudes by a circumglobal teleconnection pattern, leading to strong (weak) convective activity of MJO over the Indian Ocean. The above results offer new viewpoints about the process from springtime Atlantic SSTA signals to summertime atmospheric oscillation, and then to the MJO of tropical atmosphere affecting wintertime Pacific ENSO events, which connects different oceans. 相似文献
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应用广西壮族自治区国家气象站降水,NCEP/NCAR逐日再分析资料,NOAA逐日向外长波辐射(OLR)等逐日资料,NOAA-CPC热带大气季节内振荡(MJO)指数等,使用经验正交函数分解方法分析了广西冬季降水的气候特征;用功率谱、带通滤波、相关分析和滞后线性回归等方法,以及定义MJO相关降水事件,研究了广西冬季降水异常偏多年的降水低频特征及其与MJO的联系。(1)广西冬季降水特征以全区一致型分布为主;冬季降水异常偏多年份的逐日降水具有14~26 d的低频周期。(2) MJO强对流在赤道印度洋东部发展并东传到西太平洋热带地区时,广西可出现冬季持续强降水。(3)当MJO异常对流在印度洋东部热带地区产生,中南半岛地区到华南地区上空为异常低频偏南和偏西南气流,有利于降水形成;当印度洋东部热带地区为MJO对流抑制区,华南地区上空为异常低频偏东气流控制,不利于降水产生。(4)华南地区上空大气环流的异常是由热带印度洋地区的MJO对流激发的Rossby波列造成。 相似文献
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This paper investigates the contrasts between strong and weak Madden-Julian
Oscillation (MJO) activity over the equatorial western Pacific during winter using the NCEP
reanalysis data. It is shown that the MJO over the equatorial western Pacific in winter shows
significant interannual and interdecadal variabilities. During the winters with strong MJO
activity, an anomalous cyclonic circulation lies east of the Philippines, strong anomalous
easterlies control the equatorial eastern Pacific, and anomalous westerlies extend from the
Indian Ocean to the western Pacific in the lower troposphere, which strengthens the
convergence and convection over the equatorial western Pacific. The moisture convergence in
the lower troposphere is also enhanced over the western Pacific, which is favorable to the
activity of MJO. Eastward propagation is a significant feature of the MJO, though there is
some westward propagation. The space-time spectral power and center period of the MJO are
higher during strong MJO activity winters. The anomalous activity of MJO is closely related to
the sea surface temperature (SST) and East Asian winter monsoon (EAWM). During strong MJO
activity winters, there are positive/negative anomalies at high/low latitudes in both sea
level pressure and 500 hPa geopotential height, and the temperature is lower over the central
part of the Chinese mainland, which indicates a strong EAWM. China experiences more rainfall
between the Yellow and Yangtze Rivers, but less rainfall south of the Yangtze River. The SSTA
is negative near the Taiwan Island due to the impact of strong EAWM and shows a La Ni?a
pattern anomaly over the eastern Pacific. During the weak MJO activity winters, the situation
is reversed. 相似文献
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The summer monsoon rainfall over India exhibits strong intraseasonal variability. Earlier studies have identified Madden Julian Oscillation (MJO) as one of the most influencing factors of the intraseasonal variability of the monsoon rainfall. In this study, using India Meteorological Department (IMD) high resolution daily gridded rainfall data and Wheeler?CHendon MJO indices, the intra-seasonal variation of daily rainfall distribution over India associated with various Phases of eastward propagating MJO life cycle was examined to understand the mechanism linking the MJO to the intraseasonal variability. During MJO Phases of 1 and 2, formation of MJO associated positive convective anomaly over the equatorial Indian Ocean activated the oceanic tropical convergence zone (OTCZ) and the resultant changes in the monsoon circulation caused break monsoon type rainfall distribution. Associated with this, negative convective anomalies over monsoon trough zone region extended eastwards to date line indicating weaker than normal northern hemisphere inter tropical convergence zone (ITCZ). The positive convective anomalies over OTCZ and negative convective anomalies over ITCZ formed a dipole like pattern. Subsequently, as the MJO propagated eastwards to west equatorial Pacific through the maritime continent, a gradual northward shift of the OTCZ was observed and negative convective anomalies started appearing over equatorial Indian Ocean. During Phase 4, while the eastwards propagating MJO linked positive convective anomalies activated the eastern part of the ITCZ, the northward propagating OTCZ merged with monsoon trough (western part of the ITCZ) and induced positive convective anomalies over the region. During Phases 5 and 6, the dipole pattern in convective anomalies was reversed compared to that during Phases 1 and 2. This resulted active monsoon type rainfall distribution over India. During the subsequent Phases (7 and 8), the convective and lower tropospheric anomaly patterns were very similar to that during Phase 1 and 2 except for above normal convective anomalies over equatorial Indian Ocean. A general decrease in the rainfall was also observed over most parts of the country. The associated dry conditions extended up to northwest Pacific. Thus the impact of the MJO on the monsoon was not limited to the Indian region. The impact was rather felt over larger spatial scale extending up to Pacific. This study also revealed that the onset of break and active events over India and the duration of these events are strongly related to the Phase and strength of the MJO. The break events were relatively better associated with the strong MJO Phases than the active events. About 83% of the break events were found to be set in during the Phases 7, 8, 1 and 2 of MJO with maximum during Phase 1 (40%). On the other hand, about 70% of the active events were set in during the MJO Phases of 3 to 6 with maximum during Phase 4 (21%). The results of this study indicate an opportunity for using the real time information and skillful prediction of MJO Phases for the prediction of break and active conditions which are very crucial for agriculture decisions. 相似文献
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Possible Impacts of the Arctic Oscillation on the Interdecadal Variation of Summer Monsoon Rainfall in East Asia 总被引：18，自引：5，他引：18
The influences of the wintertime AO (Arctic Oscillation) on the interdecadal variation of summer monsoon rainfall in East Asia were examined. An interdecadal abrupt change was found by the end of the 1970s in the variation of the AO index and the leading principal component time series of the summer rainfall in East Asia, The rainfall anomaly changed from below normal to above normal in central China, the southern part of northeastern China and the Korean peninsula around 1978. However,the opposite interdecadal variation was found in the rainfall anomaly in North China and South China.The interdecadal variation of summer rainfall is associated with the weakening of the East Asia summer monsoon circulation. It is indicated that the interdecadal variation of the AO exerts an influence on the weakening of the monsoon circulation. The recent trend in the AO toward its high-index polarity during the past two decades plays important roles in the land-sea contrast anomalies and wintertime precipitation anomaly. The mid- and high-latitude regions of the Asian continent are warming, while the low-latitude regions are cooling in winter and spring along with the AO entering its high-index polarity after the late 1970s. In the meantime, the precipitation over the Tibetan Plateau and South China is excessive, implying an increase of soil moisture. The cooling tendency of the land in the southern part of Asia will persist until summer because of the memory of soil moisture. So the warming of the Asian continent is relatively slow in summer. Moreover, the Indian Ocean and Pacific Ocean which are located southward and eastward of the Asian land, are warming from winter to summer. This suggests that the contrast between the land and sea is decreased in summer. The interdecadal decrease of the land-sea heat contrast finally leads to the weakening of the East Asia summer monsoon circulation. 相似文献
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The 2016 summer floods in China and associated physical mechanisms: A comparison with 1998 下载免费PDF全文
下载免费PDF全文 Yuan Yuan Hui Gao Weijing Li Yanju Liu Lijuan Chen Bin Zhou Yihui Ding 《Acta Meteorologica Sinica》2017,31(2):261-277
The characteristics of droughts and floods in China during the summers (May–August) of 2016 and 1998 were compared in great detail, together with the associated atmospheric circulations and external-forcing factors. Following results are obtained. (1) The precipitation was mostly above normal in China in summer 2016, with two main rainfall belts located in the Yangtze River valley (YRV) and North China. Compared with 1998, a similar rainfall belt was located over the YRV, with precipitation 100% and more above normal. However, the seasonal processes of Meiyu were different. A typical “Secondary Meiyu” occurred in 1998, whereas dry conditions dominated the YRV in 2016. (2) During May–July 2016, the Ural high was weaker than normal, but it was stronger than normal in 1998. This difference resulted from fairly different distributions of sea surface temperature anomalies (SSTAs) over the North Atlantic Ocean during the preceding winter and spring of the two years. (3) Nonetheless, tropical and subtropical circulation systems were much more similar in May–July of 2016 and 1998. The circulation systems in both years were characterized by a stronger than normal and more westward-extending western Pacific subtropical high (WPSH), a weaker than normal East Asian summer monsoon (EASM), and anomalous convergence of moisture flux in the mid and lower reaches of the YRV. These similar circulation anomalies were attributed to the similar tropical SSTA pattern in the preceding seasons, i.e., the super El Niño and strong warming in the tropical Indian Ocean. (4) Significant differences in the circulation pattern were observed in August between the two years. The WPSH broke up in August 2016, with its western part being combined with the continental high and persistently dominating eastern China. The EASM suddenly became stronger, and dry conditions prevailed in the YRV. On the contrary, the EASM was weaker in August 1998 and the “Secondary Meiyu” took place in the YRV. The Madden–Julian Oscillation (MJO) was extremely active in August 2016 and stayed in western Pacific for 25 days. It triggered frequent tropical cyclone activities and further influenced the significant turning of tropical and subtropical circulations in August 2016. In contrast, the MJO was active over the tropical Indian Ocean in August 1998, conducive to the maintenance of a strong WPSH. Alongside the above oceanic factors and atmospheric circulation anomalies, the thermal effect of snow cover over the Qinghai–Tibetan Plateau from the preceding winter to spring in 2016 was much weaker than that in 1998. This may explain the relatively stronger EASM and more abundant precipitation in North China in 2016 than those in 1998. 相似文献
18.
Summary Due to the strong variation of the Asian monsoon, many countries in Asia often suffer from serious natural disasters. Droughts and floods appear in East China frequently related to the large anomalies of the two branches of East Asian monsoon. Based on rainfall data recorded by 336 Chinese stations in the 1980s, two distinctly opposite rainfall types over East China in summer (JJA) are discovered. Correspondly, 850 hPa anomalous wind fields in the Eastern Hemisphere are also possessed by two types of converse patterns in spring (MAM) and summer (JJA). The onset time and intensity of the Somali jet and the two branches of Southeast and Indian monsoon are quite different. Furthermore, in the 500 hPa geopotential height anomaly fields in spring and summer, the variations of the previous general atmospheric circulation (in spring) are closely correlated to the two kinds of conversely distributed rainfall in summer. These two types of rainfall are also related to two types of conversely distributed sea surface temperature anomaly (SSTA) in the equatorial Pacific and Indian Oceans. To investigate model capabilities refelecting the above observed features, eight numerical experiments are carried out using the IAP 2-L AGCM, with observed monthly mean global SSTs as external forcing and observed atmospheric data on February 15 as initial conditions. The simulated distributions of rainfall anomalies over East China in summer are in good accordance with observations. With conversely distributed SSTAs in the equatorial Pacific, the simulated 850 hPa anomalous wind fields and the 500 hPa geopotential height anomalies are also conversely distributed, and are closely related to the two types of simulated rainfall anomalies over East China. The cross equatorial wind varies in strength, space and time. The simulated distributions of anomalous 500 hPa geopotential height in spring and the anomalous wind at 850 hPa in spring and summer are quite similar to observations.With 10 Figures 相似文献
19.
热带大气季节内振荡对西南地区东部夏季降水的影响及其可能机制 总被引：3，自引：2，他引：1
利用1979~2013年6~8月的西南地区东部20个台站日降水量资料、逐日MJO(Madden-Julian Oscillation)指数、全球OLR(Outgoing Longwave Radiation)逐日格点资料以及NCEP/NCAR再分析日资料,采用合成分析和线性回归等方法,对夏季MJO不同位相活动影响西南地区东部夏季降水的原因及其可能机制进行了初步分析。研究表明,MJO与西南地区东部夏季降水之间存在着显著的关系,当MJO处于第4(第6)位相时,由于西太平洋副高位置偏南(偏北)、向西南地区东部的水汽输送偏多(偏少),在异常上升(下沉)气流影响下,西南地区东部夏季降水偏多(偏少)。MJO影响西南地区东部夏季降水的可能原因是:当MJO处于第4位相时,赤道东印度洋地区上空大气释放凝结潜热,其激发东北向传播的异常波动,进而影响东亚环流,使得西南地区东部出现夏季降水偏多的环流形势,西南地区东部夏季降水增多;但在第6位相时,西太平洋地区上空对流释放的凝结潜热,其激发PJ(太平洋-日本)型Rossby波列,出现不利于西南地区东部夏季降水的环流形势,西南地区东部夏季降水偏少。 相似文献
20.
内蒙古夏季降水变率的优势模态及其环流特征 总被引：3，自引：1，他引：2
本文基于1961～2013年的中国气象局降水资料以及NCEP/NCAR再分析资料,针对内蒙古地区夏季降水,利用经验正交函数分解法（EOF）和合成分析法,考察了年际尺度上内蒙古地区夏季降水分布的不同类型,并分析其前两个模态的典型环流形势以及相关的春夏季节转换特征。内蒙古夏季降水在年际尺度上主要分为整体一致型和东西反向型。整体一致型模态以贝加尔湖北侧和南侧对流层中上层环流的反位相变化、源于伊朗北部-中亚地区的中纬度遥相关型波列以及东亚地区“东高西低”或“西高东低”的环流形势为主要特征。而东西反向型模态以东欧平原-乌拉尔山东侧-内蒙古东部及东北地区为异常中心的波状环流以及东亚沿岸中高纬地区偶极子环流异常（“北高南低”或“北低南高”）为主要特征。这两种夏季降水模态的正负位相分别对应着亚洲中高纬环流春夏季节转换提前和滞后的情形。这些结论有助于进一步认识内蒙古地区夏季降水异常及其典型环流特征,从而为其预测提供参考依据。 相似文献