准两年振荡及其对东亚大气环流和气候的影响

通过多年资料分析,本文研究了平流层准两年振荡(QBO)的演变特征及其对东亚及西太平洋地区大气环流和气候变化的影响.结果表明,平流层QBO的演变特征是:东风向西风转换最早出现在印度洋赤道地区;西风向东风转换最早出现在美洲和西太平洋赤道地区.中国东部降水量、气温以及西太平洋副高和东亚急流都有准两年周期变化,并同平流层QBO有密切关系;平流层QBO对西太平洋台风活动也有一定影响,QBO的西风位相期西太平洋台风偏少.另外,ENSO对于平流层QBO有明显影响,一般在ENSO发生之后,QBO的西风位相期持续时间缩短.     

Recent advances in studies of the interaction between the East Asian winter and summer monsoons and ENSO cycle

Recent advances in studies on the interaction between the East Asian monsoon and the ENSO cycle are reviewed in this paper. Through the recent studies, not only have the responding features and processes of the East Asian winter and summer monsoon circulation anomalies and summer rainfall anomalies in East Asia to the ENSO cycle during its different stages been understood further, but also have the thermal and dynamic effects of the tropical western Pacific on the ENSO cycle been deeply analyzed from the observational facts and dynamic theories. The results of observational and theoretical studies showed that the dynamical effect of the atmospheric circulation and zonal wind anomalies in the lower troposphere over the tropical western Pacific on the ENSO cycle may be through the excitation of the equatorial oceanic Kelvin wave and Rossby waves in the equatorial Pacific. These studies demonstrated further that the ENSO cycle originates from the tropical western Pacific. Moreover, these recent studies also showed that the atmospheric circulation and zonal wind anomalies over the tropical western Pacific not only result from the air-sea interaction over the tropical western Pacific, but are also greatly influenced by the East Asian winter and summer monsoons. Additionally, the scientific problems in the interaction between the Asian monsoon and the ENSO cycle which should be studied further in the near future are also pointed out in this paper.     

东亚季风的准两年振荡及其与ENSO变率的联系

运用小波分析方法和相关分析对东亚季的准两年振荡的存在及其与ＥＮＳＯ变率的关系进行了研究,结果指出：东亚季风具有显著的准两年振荡特征,但周期与振幅具有明显的年代际变化,同时东亚季风的ＱＢＯ过程与ＥｌＮｉｎｏ事件具有密切的联系;     

Connection of stratospheric QBO with global atmospheric general circulation and tropical SST. Part I: methodology and composite life cycle

The stratospheric quasi-biennial oscillation (QBO) and its association with the interannual variability in the stratosphere and troposphere, as well as in tropical sea surface temperature anomalies (SSTA), are examined in the context of a QBO life cycle. The analysis is based on the ERA40 and NCEP/NCAR reanalyses, radiosonde observations at Singapore, and other observation-based datasets. Both reanalyses reproduce the QBO life cycle and its associated variability in the stratosphere reasonably well, except that some long-term changes are detected only in the NCEP/NCAR reanalysis. In order to separate QBO from variability on other time scales and to eliminate the long-term changes, a scale separation technique [Ensemble Empirical Mode Decomposition (EEMD)] is applied to the raw data. The QBO component of zonal wind anomalies at 30?hPa, extracted using the EEMD method, is defined as a QBO index. Using this index, the QBO life cycle composites of stratosphere and troposphere variables, as well as SSTA, are constructed and examined. The composite features in the stratosphere are generally consistent with previous investigations. The correlations between the QBO and tropical Pacific SSTA depend on the phase in a QBO life cycle. On average, cold (warm) SSTA peaks about half a year after the maximum westerlies (easterlies) at 30?hPa. The connection of the QBO with the troposphere seems to be associated with the differences of temperature anomalies between the stratosphere and troposphere. While the anomalies in the stratosphere propagate downward systematically, some anomalies in the troposphere develop and expand vertically. Therefore, it is possible that the temperature difference between the troposphere and stratosphere may alter the atmospheric stability and tropical deep convection, which modulates the Walker circulation and SSTA in the equatorial Pacific Ocean.     

Sub-seasonal interannual variability associated with the excess and deficit Indian winter monsoon over the Western Himalayas

During the winter season (Dec., Jan., and Feb.; DJF) the western Himalaya (WH) receives one-third of its annual precipitation due to Indian winter monsoon (IWM). The IWM is characterized by eastward-moving synoptic weather systems called western disturbances. Seasonal interannual precipitation variability is positively correlated with monthly interannual variabilities. However, it was found that the monthly interannual variabilities differ. The interannual variability for Jan. is negatively correlated with that for Dec. and Feb. Because the entire seasonal interannual variability is in phase with the El Niño Southern Oscillation, it is interesting to investigate such contrasting behavior. Composite analysis based on extreme wet and dry seasons indicates that Dec. and Feb. precipitation variabilities have a high positive (low negative) correlation with eastern (western) equatorial Pacific warming (cooling), whereas Jan. precipitation variability exhibits negligible correlations. Seasonal mid/upper tropospheric cooling over the Himalayas enhances anomalous cyclonic circulation, which along with suppressed convection over the western equatorial Pacific, shifts the 200-hPa subtropical westerly jet southward over the Himalayas. Due to the upper tropospheric anomalous cyclonic circulation, mass transfer favors anticyclone formation at the mid/lower troposphere, which is enhanced in Jan. due to a warmer mid troposphere and hence decreases precipitation compared with Dec. and Feb. Additionally, a weakening of meridional moisture flux transport from the equatorial Indian Ocean to WH is observed in Jan. Further analysis reveals that mid-tropospheric and surface temperatures over WH also play dominant roles, acting as local forcing where the preceding month’s surface temperature controls the succeeding month’s precipitation.     

东亚夏季风降水年代际变异模态及其与太平洋年代际振荡的关系

利用全球陆地月平均降水资料、英国气象局哈德莱中心的月平均海表温度距平(SSTA)资料及NCEP/NCAR再分析大气环流资料,探讨东亚夏季风降水年代际变率及其与太平洋年代际振荡(PDO)的联系。研究指出:东亚夏季风降水年代际变异模态以及PDO均在1976年前后呈现显著的年代际转折,并且东亚夏季风降水与PDO在年代际尺度上具有较好的相关关系。PDO能够在对流层低层激发出与年代际东亚夏季风环流较为相似的大气环流异常特征,表明东亚夏季风环流的年代际变化可能受大气外强迫因子PDO在对流层低层的外源强迫作用影响,最终导致东亚夏季风降水发生年代际变化。     

赤道西太平洋-印度洋海温异常对亚洲夏季风的影响

本文采用了p-σ五层原始方程模式模拟并研究了赤道西太平洋-印度洋海温距平场对亚洲夏季风的影响,计算了四种不同的海温距平试验方案。试验结果表明赤道西太平洋海温正距平使对流层下层的印度低压明显加强,副高北挺,季风槽加深,同时加强了对流层上层的反气旋环流。赤道西印度洋暖海温的模拟结果与赤道西太平洋暖海温对上述系统的影响相反,而赤道西印度洋冷海温对季风环流的影响与赤道西太平洋暧海温的影响一致。试验进一步表明赤道西太平洋-印度洋海温距平的纬向梯度方向对亚洲夏季风的影响是主要的,这一结论与实际观测结果一致。本文进一步讨论了赤道海温距平对越赤道气流、印度洋赤道东-西纬向环流和非绝热加热场的影响,结果都表明赤道西太平洋海温正距平和赤道西印度洋海温负距平的模拟特征与反El Nino年亚洲夏季环流特征类似,而赤道西印度洋海员正距平的模拟特征与El Nino年亚洲夏季坏流特征类似。     

THE TIMING OF SOUTH-ASIAN HIGH ESTABLISHMENT AND ITS RELATION TO TROPICAL ASIAN SUMMER MONSOON AND PRECIPITATION OVER EAST-CENTRAL CHINA IN SUMMER

The timing of the South Asian High (SAH) establishment over the Indochina Peninsula (IP) from April to May and its relations to the setup of the subsequent tropical Asian summer monsoon and precipitation over eastern-central China in summer are investigated by using NCEP/NCAR daily reanalysis data, outgoing longwave radiation (OLR) data and the daily precipitation data from 753 weather stations in China. It is found that the transitions of the zonal wind vertical shear and convection establishment over tropical Asia are earlier (later) in the years of early (late) establishment of SAH. In the lower troposphere, anti-cyclonic (cyclonic) anomaly circulation dominates the equatorial Indian Ocean. Correspondingly, the tropical Asian summer monsoon establishes earlier (later). Furthermore, the atmospheric circulation and the water vapor transport in the years of advanced SAH establishment are significantly different from the delayed years in Asia in summer. Out-of-phase distribution of precipitation in eastern-central China will appear with a weak (strong) SAH and western Pacific subtropical high, strong (weak) ascending motion in the area south of Yangtze River but weak (strong) ascending motion in the area north of it, and cyclonic (anti-cyclonic) water vapor flux anomaly circulation from the eastern-central China to western Pacific. Accordingly, the timing of the SAH establishment at the upper levels of IP is indicative of the subsequent onset of the tropical Asian summer monsoon and the flood-drought pattern over eastern-central China in summer.     

东亚季风指数及其与大尺度热力环流年际变化关系

将东西向海平面气压差与低纬度高、低层纬向风切变相结合 ,定义了东亚季风指数 ,该季风指数较好地反映了东亚冬、夏季风变化。其中 ,夏季风指数年际异常对西太平洋副热带高压南北位置变化和长江中下游旱涝具有较强的反映能力。分析表明 :东亚夏季风年际变化与印度洋 -西太平洋上空反 Walker环流及夏季越赤道南北半球间的季风环流呈显著正相关关系。在强、弱异常东亚夏季风年份 ,异常的 Walker环流在西太平洋上的辐合 (辐散 )中心在垂直方向不重合 ,高层 ( 2 0 0 h Pa)速度势与东亚夏季风显著相关区域位于西北太平洋上 ,该异常环流的高层的辐合 (辐散 )通过改变低层空气质量而影响夏季 50 0 h Pa西北太平洋副热带高压。采用 SVD分析进一步发现 :与海温耦合的异常 Walker环流在西太平洋上空的上升支表现出南北半球关于赤道非对称结构 ,亚澳季风区受该异常 Walker环流控制。因而 ,东亚季风与热带海气相互作用可直接通过这种纬向非对称的 Walker环流发生联系。     

The propagation characteristics of interannual low-frequency oscillations in the tropical air-sea system

The time series of sea surface temperature (SST), sea level pressure (SLP), zonal wind (U) and total cloudiness (CA), for the period of 1950-1979, over a 8o×8o grid-point latitudinal belt between 32oS and 32oN are made from COADS (Comprehensive Ocean-Atmosphere Data Set). The time harmonic analysis and power spectra analysis show that there exist quasi-biennial oscillation (QBO), three and half years oscillation (SO), five and half years oscillation (FYO) and eleven years oscillation (EYO) in these time series. The main propagation characteristics of these interannual low-frequency oscillations are as follows:(1) The variance analysis of SST shows that there is an active region of QBO and SO (with maximum variance), coming from the southwestern part of the subtropical Pacific, stretching eastward up to the west coast of South America, and then northward to the eastern equatorial Pacific. The QBO and SO disturbances of SST follow the same route and cause the anomaly of SST (El Nino and period of cold water) in the eastern equatorial Pacific.(2) Either the QBO or SO of SST can cause El Nino events, although it is easier when they are situated in the same phase of warm water at the eastern equatorial Pacific. The FYO of SST seems to be a standing oscillation. It plays an important role on the formation of strong El Nino events or strong cold water events.(3) The QBO and SO of U propagate eastward along the equator. The origin of QBO and SO may at least be traced as far as the western Indian Ocean. While they propagate along the equator, it strengthens two times at 90oE and the western Pacific, respectively. Like SST, the FYO of U is somehow a standing oscillation.(4) The Oscillations of U have a good coupling relationship with those of SST, while they propagate. When the QBO and SO of SST move to the east side of the eastern equatorial Pacific, it is the time for the QBO and SO of U to enter into the east part of the western Pacific.It is clear that, when we do research work on the formation of El Nino events, our consideration would not be confined to the tropics, it should cover the subtropical region in the southern Pacific. The features of the circulation and other oceanic states in this area are very important to the El Nino events.     

近百年东亚冬季风与ENSO循环的相互关系及其年代际异常

运用相关及滑动相关的计算技术，讨论了近百年东亚冬季风与ENSO循环的相互关系及其年代际异常。研究指出，东亚冬季风与赤道东太平洋海温的年际关系具有年代际的变化特征；季风与ENSO循环的关系受到季风的QBO以及季风-海洋的年代际背景场配置关系的共同作用；当季风与海洋的背景场处于同样状态时，强冬季风有利于第二年冬季赤道东太平洋的升温，产生El Ni?o事件；当两者的背景场处于反位相状态时，强冬季风对应于第二年冬季的La Ni?a位相。     

东亚-北太平洋偶极型气压场及其与东亚季风年际变化的关系

利用美国NCEP/NCAR的月平均再分析资料,研究东亚-太平洋地区地面气压的耦合模态与东亚副热带季风异常的关系,结果表明:在亚洲大陆和北半球太平洋之间气压场的偶极子模态主要反映了东亚地区东西向气压梯度的异常.从20世纪60年代到70年代中期,东亚-太平洋的这种偶极子表现为蒙古地区气压偏低和太平洋地区气压偏高的特征,而从20世纪70年代后期到90年代,则表现为蒙古地区气压偏高和太平洋地区气压偏低的特征.在偶极子指数值较高的年份,冬季(或夏季)蒙古高压(或蒙古低压)和太平洋阿留申低压(或太平洋副热带高压)较强     

EI Nino现象对东亚夏季风环流影响的初步研究

本文分析了1971—80年发生在南美洲西海岸的EI Nino现象及其对东亚夏季风环流的影响。结果表明,1972和1976年为强的EI Nino年,而1971和1974年为显著的反EI Nino年。还指出,1—6月份南美西海岸的海温与7月份我国东部大部分地区夏季风呈负相关.在EI Nino年,主要环流的特征为:(1)西太平洋副热带高压脊线偏北,强度偏弱.(2)澳大利亚高压位置偏南。(3)赤道缓冲脊强大.ITCZ东伸到太平洋中部。南半球的信风在105°E附近越过赤道之后,于10°N折向东去,流入西太平洋.(4)印度次大陆季风中断.孟湾西南季风直接影响我国东部地区的分量极其有限,在反EI Nino年,上述各系统特征完全相反.我们认为,EI Nino现象的发生,引起夏季风环流系统的变动,最终影响到我国夏季风的强度,这是二者之间遥相关的一种可能过程.      

Modulation of low frequency intraseasonal oscillations of northern summer monsoon by El Nino and Southern Oscillation (ENSO)

Summary In order to improve our understanding of the interannual variability of the 30–50 day oscillations of the northern summer monsoon, we have performed numerical experiments using a 5-level global spectral model (GSM). By intercomparing the GSM simulations of a control summer experiment (E1) and a warm ENSO experiment (E2) we have examined the sensitivity of the low frequency intraseasonal monsoonal modes to changes in the planetary scale component of the monsoon induced by anomalous heating in the equatorial eastern Pacific during a warm ENSO phase.It is found that the anomalous heating in the equatorial eastern Pacific induces circulation changes which correspond to weakening of the time-mean divergent planetary scale circulation in the equatorial western Pacific, weakening of the east-west Walker cell over the western Pacific ocean, weakening of the time-mean Reverse Hadley circulation (RHC) over the summer monsoon region and strengthening of the time-mean divergent circulation and the subtropical jet stream over the eastern Pacific and Atlantic oceans. These changes in the large scale basic flow induced by the anomalous heat source are found to significantly affect the propagation characteristics of the 30–50 day oscillations. It is noticed that the reduction (increase) in the intensity of the time-mean divergent circulation in the equatorial western (eastern) Pacific sectors produces weaker (stronger) low-level convergence as a result of which the amplitude of the eastward propagating 30–50 day divergent wave decreases (increases) in the western (eastern) Pacific sectors in E2. One of the striking aspects is that the eastward propagating equatorial wave arrives over the Indian longitudes more regularly in the warm ENSO experiment (E2). The GSM simulations reveal several small scale east-west cells in the longitudinal belt between 0–130°E in the E1 experiment. On the other hand the intraseasonal oscillations in E2 show fewer east-west cells having longer zonal scales. The stronger suppression of small scale east-west cells in E2 probably accounts for the greater regularity of the 30–50 day oscillations over the Indian longitudes in this case.The interaction between the monsoon RHC and the equatorial 30–50 day waves leads to excitation of northward propagating modes over the Indian subcontinent in both cases. It is found that the zonal wind perturbations migrate northward at a rate of about 0.8° latitude per day in E1 while they have a slightly faster propagation speed of about 1° latitude per day in E2. The low frequency monsoonal modes have smaller amplitude but possess greater regularity in E2 relative to E1. As the wavelet trains of low latitude anomalies progress northward it is found that the giant meridional monsoonal circulation (RHC) undergoes well-defined intraseasonal oscillations. The amplitude of the monsoon RHC oscillations are significantly weaker in E2 as compared to E1. But what is more important is that the RHC is found to oscillate rapidly with a period of 40 days in E1 while it executes slower oscillations of 55 days period in E2. These results support the observational findings of Yasunari (1980) who showed that the cloudiness fluctuations on the 30–60 day time scale over the Indian summer monsoon region are associated with longer periods during El Nino years. The oscillations of the monsoon RHC show an enhancement of the larger scale meridional cells and also a stronger suppression of the smaller scale cells in E2 relative to E1 which seems to account for the slower fluctuations of the monsoon RHC in the warm ENSO experiment. It is also proposed that the periodic arrival of the eastward propagating equatorial wave over the Indian longitudes followed by a stronger inhibition of the smaller meridional scales happen to be the two primary mechanisms that favour steady and regular northward propagation of intraseasonal transients over the Indian subcontinent in the warm ENSO experiment (E2). This study clearly demonstrates that the presence of E1 Nino related summertime SST anomalies and associated convection anomalies in the tropical central and eastern Pacific are favourable criteria for the detection and prediction of low frequency monsoonal modes over India.With 11 Figures     

春季热带南大西洋海表温度异常与夏季亚澳季风区降水异常的联系

利用1979—2019年Hadley中心的海表温度资料、GPCP的降水资料以及NCEP-DOE的再分析资料等,分析了北半球春季热带南大西洋海表温度异常与北半球夏季亚澳季风区降水异常的联系。研究表明,北半球春季热带南大西洋海表温度异常与随后夏季热带西太平洋到南海（澳大利亚东侧海域到热带东印度洋）地区的降水异常为显著负相关（正相关）关系。北半球春季热带南大西洋的海表温度正异常可以引起热带大西洋和热带太平洋间的异常垂直环流,其中异常上升支（下沉支）位于热带大西洋（热带中太平洋）。热带中太平洋的异常下沉气流和低层辐散气流引起热带中西太平洋低层的异常东风,后者有利于热带中东太平洋海表温度出现负异常。通过Bjerknes正反馈机制,热带中东太平洋海表温度异常从北半球春季到夏季得到发展。热带中东太平洋海表温度负异常激发的Rossby波使得北半球夏季热带西太平洋低层出现一对异常反气旋。此时,850 hPa上热带西太平洋到海洋性大陆地区为显著的异常东风,有利于热带西太平洋到南海（澳大利亚东侧海域到热带东印度洋）地区出现异常的水汽辐散（辐合）,导致该地区降水减少（增加）。     

Role of TBO and ENSO scale ocean–atmosphere interaction in the Indo-Pacific region on Asian summer monsoon variability

Interannual variability of the Indian summer monsoon rainfall has two dominant periodicities, one on the quasi-biennial (2–3 year) time scale corresponding to tropospheric biennial oscillation (TBO) and the other on low frequency (3–7 year) corresponding to El Niño Southern Oscillation (ENSO). In the present study, the spatial and temporal patterns of various atmospheric and oceanic parameters associated with the Indian summer monsoon on the above two periodicities were investigated using NCEP/NCAR reanalysis data sets for the period 1950–2005. Influences of Indian and Pacific Ocean SSTs on the monsoon season rainfall are different for both of the time scales. Seasonal evolution and movement of SST and Walker circulation are also different. SST and velocity potential anomalies are southeast propagating on the TBO scale, while they are stationary on the ENSO scale. Latent heat flux and relative humidity anomalies over the Indian Ocean and local Hadley circulation between the Indian monsoon region and adjacent oceans have interannual variability only on the TBO time scale. Local processes over the Indian Ocean determine the Indian Ocean SST in biennial periodicity, while the effect of equatorial east Pacific SST is significant in the ENSO periodicity. TBO scale variability is dependent on the local factors of the Indian Ocean and the Indian summer monsoon, while the ENSO scale processes are remotely controlled by the Pacific Ocean.     

INTERRELATION BETWEEN EAST-ASIAN WINTER MONSOON AND INDIAN/PACIFIC SST WITH THE INTERDECADAL VARIATION*

Investigated statistically is the interrelation between East Asian winter monsoon (EAWM) and SST over sensitive areas of the Indian and Pacific Oceans.with focus on the relation of EAWM to strong ENSO signal area.i.e.,the equatorial eastern Pacific (EEP) SST.Evidence suggests that the EAWM variation is intimately associated not only with the EEP SST but with the equatorial western Pacific "warm pool" and equatorial Indian/northwestern Pacific Kuroshio SST as well:the EAWM and ENSO interact strongly with each other on the interannual time scales,exhibiting pronounced interdecadal variation mainly under the joint effect of the monsoon QBO and the monsoon/SST background field features on an interdecadal basis-when both fields are in the same phase(anti-phase).strong EAWM contributes to EEP SST rise(drop)in the following winter,corresponding to a warm(cold)ENSO cycle;the EAWM QBO causes ENSO cycle to be strong phase-locked with seasonal variation,making the EEP SST rise lasting from April-May to May-June of the next year,which plays an important role in maintaining a warm ENSO phase.     

Propagation and mechanisms of the quasi-biweekly oscillation over the Asian summer monsoon region

The propagation and underlying mechanisms of the boreal summer quasi-biweekly oscillation (QBWO) over the entire Asian monsoon region are investigated, based on ECMWF Interim reanalysis (ERA-Interim) data, GPCP precipitation data, and an atmospheric general circulation model (AGCM). Statistical analyses indicate that the QBWO over the Asian monsoon region derives its main origin from the equatorial western Pacific and moves northwestward to the Bay of Bengal and northern India, and then northward to the Tibetan Plateau (TP) area, with a baroclinic vertical structure. Northward propagation of the QBWO is promoted by three main mechanisms: barotropic vorticity, boundary moisture advection, and surface sensible heating (SSH). It is dominated by the barotropic vorticity effect when the QBWO signals are situated to the south of 20°N. During the propagation taking place farther north toward the TP, the boundary moisture advection and SSH are the leading mechanisms. We use an AGCM to verify the importance of SSH on the northward propagation of the QBWO. Numerical simulations confirm the diagnostic conclusion that the equatorial western Pacific is the source of the QBWO. Importantly, the model can accurately simulate the propagation pathway of the QBWO signals over the Asian monsoon region. Simultaneously, sensitivity experiments demonstrate that the SSH over northern India and the southern slope of the TP greatly contributes to the northward propagation of the QBWO as far as the TP area.     

SOI and QBO signals in the African region

Summary Climatic determinants of summer (Nov-Mar) rainfall over southern Africa are investigated through analysis of sea surface temperatures (SST), outgoing longwage radiation (OLR) and tropospheric wind with respect to the Southern Oscillation Index (SOI) and the stratospheric quasi-biennial oscillation (QBO). Index-to-field correlation maps are presented at various lags for the austral spring and summer seasons to establish the spatial dependence and evolution of coherent, statistically significant features. The SOI signal is reflected in upper-level zonal wind anomalies over the equatorial Atlantic Ocean during spring. SSTs in the central Indian Ocean are significantly negatively correlated with the SOI in summer. On the other hand, OLR correlations are weak over southern Africa in the summer, implying that the SOI signal may not dominate interannual convective variability.QBO correlations with SST are relatively weak, but with 200 hPa zonal winds over the western equatorial Ocean, positive correlations are noted. A standing wave pattern is described in the sub-tropics. The OLR correlation pattern represents a dipole with increased convection over eastern and southern Africa in contrast to reduced convection over Madagascar when the QBO is in west phase.Contingency analyses indicate that the global indices are unreliable predictors in isolation. However the characteristics and domain of influence of SOI and QBO signals are identified and may offer useful inputs to objective multivariate models for different modes of southern African rainfall variability.With 12 Figures     

THE EFFECT OF EQUATORIAL CENTRAL PACIFIC SSTAS ON THE INTERANNUAL VARIATION OF PRECIPITATION OVER SOUTHWEST CHINA DURING SPRING

The interannual variations of rainfall over southwest China (SWC) during spring and its relationship with sea surface temperature anomalies (SSTAs) in the Pacific are analyzed, based on monthly mean precipitation data from 26 stations in SWC between 1961 and 2010, NCEP/NCAR re-analysis data, and Hadley global SST data. Sensitivity tests are conducted to assess the response of precipitation in SWC to SSTAs over two key oceanic domains, using the global atmospheric circulation model ECHAM5. The interannual variation of rainfall over SWC in spring is very significant. There are strong negative (positive) correlation coefficients between the anomalous precipitation over SWC and SSTAs over the equatorial central Pacific (the mid-latitude Pacific) during spring. Numerical simulations show that local rainfall in the northwest of the equatorial central Pacific is suppressed, and a subtropical anticyclone circulation anomaly is produced, while a cyclonic circulation anomaly in the mid-latitude western Pacific occurs, when the equatorial Pacific SSTAs are in a cold phase in spring. Anomalous northerly winds appear in the northeastern part of SWC in the lower troposphere. Precipitation increases over the Maritime Continent of the western equatorial Pacific, while a cyclonic circulation anomaly appears in the northwest of the western equatorial Pacific. A trough over the Bay of Bengal enhances the southerly flow in the south of SWC. The trough also enhances the transport of moisture to SWC. The warm moisture intersects with anomalous cold air over the northeast of SWC, and so precipitation increases during spring. On the interannual time scale, the impacts of the mid-latitude Pacific SSTAs on rainfall in SWC during spring are not significant, because the mid-latitude Pacific SSTAs are affected by the equatorial central Pacific SSTAs; that is, the mid-latitude Pacific SSTAs are a feedback to the circulation anomaly caused by the equatorial central Pacific SSTAs.