How predictable is the northern hemisphere summer upper-tropospheric circulation?

The retrospective forecast skill of three coupled climate models (NCEP CFS, GFDL CM2.1, and CAWCR POAMA 1.5) and their multi-model ensemble (MME) is evaluated, focusing on the Northern Hemisphere (NH) summer upper-tropospheric circulation along with surface temperature and precipitation for the 25-year period of 1981–2005. The seasonal prediction skill for the NH 200-hPa geopotential height basically comes from the coupled models’ ability in predicting the first two empirical orthogonal function (EOF) modes of interannual variability, because the models cannot replicate the residual higher modes. The first two leading EOF modes of the summer 200-hPa circulation account for about 84% (35.4%) of the total variability over the NH tropics (extratropics) and offer a hint of realizable potential predictability. The MME is able to predict both spatial and temporal characteristics of the first EOF mode (EOF1) even at a 5-month lead (January initial condition) with a pattern correlation coefficient (PCC) skill of 0.96 and a temporal correlation coefficient (TCC) skill of 0.62. This long-lead predictability of the EOF1 comes mainly from the prolonged impacts of El Niño-Southern Oscillation (ENSO) as the EOF1 tends to occur during the summer after the mature phase of ENSO. The second EOF mode (EOF2), on the other hand, is related to the developing ENSO and also the interdecadal variability of the sea surface temperature over the North Pacific and North Atlantic Ocean. The MME also captures the EOF2 at a 5-month lead with a PCC skill of 0.87 and a TCC skill of 0.67, but these skills are mainly obtained from the zonally symmetric component of the EOF2, not the prominent wavelike structure, the so-called circumglobal teleconnection (CGT) pattern. In both observation and the 1-month lead MME prediction, the first two leading modes are accompanied by significant rainfall and surface air temperature anomalies in the continental regions of the NH extratropics. The MME’s success in predicting the EOF1 (EOF2) is likely to lead to a better prediction of JJA precipitation anomalies over East Asia and the North Pacific (central and southern Europe and western North America).     

Equatorial pacific SSTA-related decadal variations of potential predictability of ENSO and interannual climate

Summary Based on analysis of NCEP reanalysis data and SST indices of the recent 50 years, decadal changes of the potential predictability of ENSO and interannual climate anomalies were investigated. Autocorrelation of Nino3 SST anomalies (SSTA) and correlation between atmospheric anomalies fields and Nino3 SSTA exhibit obvious variation in different decades, which indicates that Nino3 SSTA-related potential predictability of ENSO and interannual climate anomalies has significant decadal changes. Time around 1977 is not only a shift point of climate on the interdecadal time scale but also a catastrophe point of potential predictability of ENSO and interannual climate. As a whole, ENSO and the PNA pattern in boreal winter are more predictable in 1980s than in 1960s and 1970s, while the Nino3 SSTA-related potential predictability of the Indian monsoon and the East Asian Monsoon is lower in 1980s than in 1960s and 1970s. Received October 19, 1999 Revised December 30, 1999     

A timescale decomposed threshold regression downscaling approach to forecasting South China early summer rainfall

A timescale decomposed threshold regression(TSDTR) downscaling approach to forecasting South China early summer rainfall(SCESR) is described by using long-term observed station rainfall data and NOAA ERSST data. It makes use of two distinct regression downscaling models corresponding to the interannual and interdecadal rainfall variability of SCESR.The two models are developed based on the partial least squares(PLS) regression technique, linking SCESR to SST modes in preceding months on both interannual and interdecadal timescales. Specifically, using the datasets in the calibration period 1915–84, the variability of SCESR and SST are decomposed into interannual and interdecadal components. On the interannual timescale, a threshold PLS regression model is fitted to interannual components of SCESR and March SST patterns by taking account of the modulation of negative and positive phases of the Pacific Decadal Oscillation(PDO). On the interdecadal timescale, a standard PLS regression model is fitted to the relationship between SCESR and preceding November SST patterns. The total rainfall prediction is obtained by the sum of the outputs from both the interannual and interdecadal models. Results show that the TSDTR downscaling approach achieves reasonable skill in predicting the observed rainfall in the validation period 1985–2006, compared to other simpler approaches. This study suggests that the TSDTR approach,considering different interannual SCESR-SST relationships under the modulation of PDO phases, as well as the interdecadal variability of SCESR associated with SST patterns, may provide a new perspective to improve climate predictions.     

1月份两类ENSO的海气环流模态分析

本文对1950～2001年1月份的大气风场和大洋流场做了联合复EOF（Empirical Orthogonal Function）分解,用以探讨1月份两类ENSO（El Ni?o-Southern Oscillation）的海气环流及耦合情况,所得结果主要有:该分解第1、2模态空间场分别相应于东部型、中部型ENSO,前者在赤道太平洋东部和中部都有海温动力异常,并以东部异常最强,后者仅在中部存在此异常,两模态的时间系数都与ENSO有很好相关,为此第1、2模态可分别称为东部型、中部型ENSO的风场流场（异常）模态。东部型ENSO模态具有3～6年的年际变化和13～14年的年代际变化,中部型则有明显的7年年际变化和12、17年的年代际变化,两者中约13年的周期与冬季北太平洋NPGO（North Pacific Gyre Oscillation）的周期相同。东、中部型El Ni?o期间,沃克环流上升支分别从印尼东移至赤道西、中太平洋,并有所减弱;南、北支哈得莱环流则分别位于日界线以东及该线附近,且均有所加强,从而使南、北太平洋副热带高压偏强;而在5°S的南美沿岸则分别有垂直运动上升和下沉异常。在海气耦合上,两类ENSO模态在赤道中太平洋均存在西风异常与海洋赤道Kelvin波和Rossby波的波包解耦合,而海温动力异常对大气的影响则都起到负反馈作用,从而有利于ENSO的维持和稳定。     

不同年代际背景下南半球冬季马斯克林高压影响因子的比较

利用NCEP/NCAR与ERA-40再分析资料分析了南半球冬季(JJA)马斯克林高压的年际和年代际变化特征,并重点讨论了不同年代际背景下影响马斯克林高压年际变化因子的变化。结果表明,冬季(JJA)马斯克林高压的强度在1976年前后发生了显著的年代际转折,1976年以前强度偏弱,1976年以后强度明显增强。进一步分析显示,影响马斯克林高压年际变化的因子同样也发生了年代际转折。在1976年以前,冬季马斯克林高压与印度洋局地海温和南极涛动(Ant Arctic Oscillation,AAO)表现出显著的相关性;而在1976年以后,冬季马斯克林高压与ENSO和AAO表现出显著的相关性。同时,印度洋局地海温与马斯克林高压的相关性减弱,而ENSO与马斯克林高压的相关性则显著增强。     

Interannual and interdecadal variabilities in the Pacific in an MRI coupled GCM

Interannual and interdecadal variabilities in the Pacific are investigated with a coupled atmosphere-ocean GCM developed at MRI, Japan. The model is run for 70 years with flux adjustments. The model shows interannual variability in the tropical Pacific which has several typical characteristics shared with the observed ENSO. A basin-scale feature of the principal SST variation for the ENSO time scale shows negative correlation in the central North Pacific with the tropical SST, similar to that of the observed one. Associated variation of the model atmosphere indicates an intensification of the Aleutian Low and a PNA-like teleconnection pattern as a response to the tropical warm SST anomaly. The ENSO time scale variability in the midlatitude ocean consists of the westward propagation of the subsurface temperature signal and the temperature variation within the shallow mixed layer forced by the anomalous atmospheric heat fluxes. For the interdecadal time scale, variation of the SST is simulated realistically with a geographical pattern similar to that for the ENSO time scale, but it has a larger relative amplitude in the northern Pacific. For the atmosphere, spatial structure of the variation in the interdecadal time scale is also similar to that in the ENSO time scale, but has smaller amplitude in the northern Pacific. Long oceanic spin-up time (>∼10 y) in the mid-high latitude, however, makes oceanic response in the interdecadal time scale larger than that in the ENSO time scale. The lagged-regression analysis for the ocean temperature variation relative to the wind stress variation indicates that interdecadal variation of the ocean subsurface at the mid-high latitudes is considered as enhanced ocean gyre spin-up process in response to the atmospheric circulation change at the mid-high latitudes, remotely forced by the interdecadal variation of the tropical SST. Received: 6 November 1995 / Accepted: 19 April 1996     

Seasonal prediction and predictability of the Asian winter temperature variability

Efforts have been made to appreciate the extent to which we can predict the dominant modes of December–January–February (DJF) 2 m air temperature (TS) variability over the Asian winter monsoon region with dynamical models and a physically based statistical model. Dynamical prediction was made on the basis of multi-model ensemble (MME) of 13 coupled models with the November 1 initial condition for 21 boreal winters of 1981/1982–2001/2002. Statistical prediction was performed for 21 winters of 1981/1982–2001/2002 in a cross-validated way and for 11 winters of 1999/2000–2009/2010 in an independent verification. The first four observed modes of empirical orthogonal function analysis of DJF TS variability explain 69 % of the total variability and are statistically separated from other higher modes. We identify these as predictable modes, because they have clear physical meaning and the MME reproduces them with acceptable criteria. The MME skill basically originates from the models’ ability to capture the predictable modes. The MME shows better skill for the first mode, represented by a basin-wide warming trend, and for second mode related to the Arctic Oscillation. However, the statistical model better captures the third and fourth modes, which are strongly related to El Niño and Southern Oscillation (ENSO) variability on interannual and interdecadal timescales, respectively. Independent statistical forecasting for the recent 11-year period further reveals that the first and fourth modes are highly predictable. The second and third modes are less predictable due to lower persistence of boundary forcing and reduced potential predictability during the recent years. In particular, the notable decadal change in the monsoon–ENSO relationship makes the statistical forecast difficult.     

Current status of ENSO prediction skill in coupled ocean–atmosphere models

The overall skill of ENSO prediction in retrospective forecasts made with ten different coupled GCMs is investigated. The coupled GCM datasets of the APCC/CliPAS and DEMETER projects are used for four seasons in the common 22 years from 1980 to 2001. As a baseline, a dynamic-statistical SST forecast and persistence are compared. Our study focuses on the tropical Pacific SST, especially by analyzing the NINO34 index. In coupled models, the accuracy of the simulated variability is related to the accuracy of the simulated mean state. Almost all models have problems in simulating the mean and mean annual cycle of SST, in spite of the positive influence of realistic initial conditions. As a result, the simulation of the interannual SST variability is also far from perfect in most coupled models. With increasing lead time, this discrepancy gets worse. As one measure of forecast skill, the tier-1 multi-model ensemble (MME) forecasts of NINO3.4 SST have an anomaly correlation coefficient of 0.86 at the month 6. This is higher than that of any individual model as well as both forecasts based on persistence and those made with the dynamic-statistical model. The forecast skill of individual models and the MME depends strongly on season, ENSO phase, and ENSO intensity. A stronger El Niño is better predicted. The growth phases of both the warm and cold events are better predicted than the corresponding decaying phases. ENSO-neutral periods are far worse predicted than warm or cold events. The skill of forecasts that start in February or May drops faster than that of forecasts that start in August or November. This behavior, often termed the spring predictability barrier, is in part because predictions starting from February or May contain more events in the decaying phase of ENSO.     

冬季赤道太平洋不同类型海温异常表征指数的再构建

利用1963—2013年Hadley中心月平均海表温度资料,以及NCEP/NCAR再分析资料,根据两类厄尔尼诺事件发生时北半球冬季赤道太平洋地区海温异常的不同空间分布特征,即赤道中太平洋CP型和东太平洋EP型海温异常空间分布,从寻找与之相似的空间型角度出发,设计了一组新的海温异常指数I_(CP)和I_(EP)。与以往ENSO指数相比,新指数组I_(CP)和I_(EP)不仅表示了空间上相互独立的海温异常分布,而且在相同的研究时段内,因时间域上相互独立而能更好地表征和区分两类El Ni?o/La Ni?a事件。据此,采用该新指数组探讨了与中部型和东部型海温异常事件相关的热带太平洋的主要海气耦合特征。结果表明,与传统的东部型El Ni?o事件发生时最大暖海温中心位于赤道东太平洋地区不同,中部型El Ni?o事件,异常增暖中心位于赤道中太平洋。中部型时异常Walker环流的上升支向西偏移,异常降水集中于热带中太平洋,不似东部型时异常限定于赤道东太平洋地区。不论哪类事件,海洋性大陆均可受到影响,即CP或EP型El Ni?o发生时,海洋性大陆区域降水偏少。但比较而言,中部型ENSO对海洋性大陆区域的影响更大。     

Interdecadal changes in interannual variability of the global monsoon precipitation and interrelationships among its subcomponents

The interdecadal and the interannual variability of the global monsoon (GM) precipitation over the area which is chosen by the definition of Wang and Ding (Geophys Res Lett 33: L06711, 2006) are investigated. The recent increase of the GM precipitation shown in previous studies is in fact dominant during local summer. It is evident that the GM monsoon precipitation has been increasing associated with the positive phase of the interdecadal Pacific oscillation in recent decades. Against the increasing trend of the GM summer precipitation in the Northern Hemisphere, its interannual variability has been weakened. The significant change-point for the weakening is detected around 1993. The recent weakening of the interannual variability is related to the interdecadal changes in interrelationship among the GM subcomponents around 1993. During P1 (1979–1993) there is no significant interrelationship among GM subcomponents. On the other hand, there are significant interrelationships among the Asian, North American, and North African summer monsoon precipitations during P2 (1994–2009). It is noted that the action center of the interdecadal changes is the Asian summer (AS) monsoon system. It is found that during P2 the Western North Pacific summer monsoon (WNPSM)-related variability is dominant but during P1 the ENSO-related variability is dominant over the AS monsoon region. The WNPSM-related variability is rather related to central-Pacific (CP) type ENSO rather than the eastern-Pacific (EP) type ENSO. Model experiments confirm that the CP type ENSO forcing is related to the dominant WNPSM-related variability and can be responsible for the significant interrelationship among GM subcomponents.     

Interdecadal variability of the ENSO teleconnection to the wintertime North Pacific

The El Niño/Southern Oscillation (ENSO) strongly influences the large-scale atmospheric circulation over the extratropical North Pacific during boreal winter, which has an important impact on North American winter climate. This study analyses the interdecadal variability of the ENSO teleconnection to the wintertime extratropical North Pacific, over the period 1900–2010, using a range of observationally derived datasets and an ensemble of atmospheric model simulations. The observed teleconnection strength is found to vary substantially over the 20th century. Specifically, 31-year periods in the early-century (1912–1942), mid-century (1946–1976) and the late-century (1980–2010) are identified in the observations when the ENSO teleconnection to the North Pacific circulation are found to be particularly strong, weak and strong respectively. The ENSO teleconnection to the North Pacific in the atmospheric model ensemble is weak in the mid-century period and substantially stronger in the late-century, closely following the variability in the observed ENSO-North Pacific teleconnection. In the early-century, however, the atmospheric model also exhibits a weak teleconnection to the North Pacific, unlike in observations. In a subset of the model realisations that exhibit similar ENSO-North Pacific teleconnection as in observations during the early-century period there are large differences in extratropical circulation but not in equatorial Pacific precipitation anomalies, in contrast to the late-century period. This suggests that the high correlation in the early century period is largely due to internal extratropical variability. The important implications of these results for seasonal predictability and the assessment of seasonal forecasting systems are discussed.

     

Ocean–atmosphere Teleconnections Play a Key Role in the Interannual Variability of Seasonal Gross Primary Production in China

Since the 1950s, the terrestrial carbon uptake has been characterized by interannual variations, which are mainly determined by interannual variations in gross primary production (GPP). Using an ensemble of seven-member TRENDY (Trends in Net Land–Atmosphere Carbon Exchanges) simulations during 1951–2010, the relationships of the interannual variability of seasonal GPP in China with the sea surface temperature (SST) and atmospheric circulations were investigated. The GPP signals that mostly relate to the climate forcing in terms of Residual Principal Component analysis (hereafter, R-PC) were identified by separating out the significant impact from the linear trend and the GPP memory. Results showed that the seasonal GPP over China associated with the first R-PC1 (the second R-PC2) during spring to autumn show a monopole (dipole or tripole) spatial structure, with a clear seasonal evolution for their maximum centers from springtime to summertime. The dominant two GPP R-PC are significantly related to Sea Surface Temperature (SST) variability in the eastern tropical Pacific Ocean and the North Pacific Ocean during spring to autumn, implying influences from the El Ni?o–Southern Oscillation (ENSO) and the Pacific Decadal Oscillation (PDO). The identified SST and circulation factors explain 13%, 23% and 19% of the total variance for seasonal GPP in spring, summer and autumn, respectively. A clearer understanding of the relationships of China’s GPP with ocean–atmosphere teleconnections over the Pacific and Atlantic Ocean should provide scientific support for achieving carbon neutrality targets.     

Pacific decadal oscillation and variability of the Indian summer monsoon rainfall

Recent studies have furnished evidence for interdecadal variability in the tropical Pacific Ocean. The importance of this phenomenon in causing persistent anomalies over different regions of the globe has drawn considerable attention in view of its relevance in climate assessment. Here, we examine multi-source climate records in order to identify possible signatures of this longer time scale variability on the Indian summer monsoon. The findings indicate a coherent inverse relationship between the inter-decadal fluctuations of Pacific Ocean sea surface temperature (SST) and the Indian monsoon rainfall during the last century. A warm (cold) phase of the Pacific interdecadal variability is characterized by a decrease (increase) in the monsoon rainfall and a corresponding increase (decrease) in the surface air temperature over the Indian subcontinent. This interdecadal relationship can also be confirmed from the teleconnection patterns evident from long-period sea level pressure (SLP) dataset. The SLP anomalies over South and Southeast Asia and the equatorial west Pacific are dynamically consistent in showing an out-of-phase pattern with the SLP anomalies over the tropical central-eastern Pacific. The remote influence of the Pacific interdecadal variability on the monsoon is shown to be associated with prominent signals in the tropical and southern Indian Ocean indicative of coherent inter-basin variability on decadal time scales. If indeed, the atmosphere–ocean coupling associated with the Pacific interdecadal variability is independent from that of the interannual El Niño-Southern Oscillation (ENSO), then the climate response should depend on the evolutionary characteristics of both the time scales. It is seen from our analysis that the Indian monsoon is more vulnerable to drought situations, when El Niño events occur during warm phases of the Pacific interdecadal variability. Conversely, wet monsoons are more likely to prevail, when La Niña events coincide during cold phases of the Pacific interdecadal variability.     

The retrospective prediction of ENSO from 1881 to 2000 by a hybrid coupled model: (II) Interdecadal and decadal variations in predictability

In this study, the retrospective predictions of ENSO (El Niño and Southern Oscillation) were performed for the period from 1881 to 2000 using a hybrid coupled model, which is an ocean general circulation model coupled to a linear statistical atmospheric model, and using a newly developed initialization scheme of SST assimilation by Ensemble Kalman Filter. With the retrospective predictions of the past 120 years, some important issues of ENSO predictability (measured by correlation and RMSE skills of NINO3 sea surface temperature anomaly index) were studied including decadal/interdecadal variations in ENSO predictability and the mechanisms responsible for these variations. Emphasis was placed on investigating the relationship between ENSO predictability and various characteristics of ENSO system such as the signal strength, the irregularity of periodicity, the noise and the nonlinearity. It is found that there are significant decadal/interdecadal variations in the prediction skills of ENSO during the past 120 years. The ENSO events were more predictable during the late nineteenth and the late twentieth centuries. The decadal/interdecadal variations of prediction skills are strongly related to the strength of sea-surface temperature anomaly (SSTA) signals, especially to the strength of SSTA signals at the frequencies of 2–4 year periods. The SSTA persistence, dominated by SSTA signals at frequencies over 4-year periods, also has a positive relationship to prediction skills. The high-frequency noise, on the other hand, has a strong inverse relationship to prediction skills, suggesting that it also probably plays an important role in ENSO predictability.     

Modes of SST variability and the fluctuation of global mean temperature

Annually averaged global mean land air temperature and sea surface temperature (SST) combined, and global mean SST alone share similar fluctuations. We examine contributions by modes of SST variability in the global mean SST based on a new version (version 3) of global sea-ice and SST (GISST3). Besides a trend mode, the dominant modes are El Niño-Southern Oscillation (ENSO), interhemispheric oscillation, and North Pacific oscillation. Statistics over the period of 1880–1997 show that excluding a warming trend the fluctuation on interannual (IA) and decadal-interdecadal (DID) time scales is dominated by IA ENSO and DID ENSO-like variability. However, the contribution by IA ENSO cycles experiences significant fluctuations, and there appears to be strong modulations by ENSO-like variability on DID or longer time scales: during several decade-long periods, when DID ENSO-like variability raises the temperature in the equatorial eastern Pacific, the contribution by IA ENSO cycles weakens to an insignificant level. The latest example of such modulation is the period since about 1980; despite the exceptional strength of El Niño events, the contribution by IA ENSO cycles weakens, suggesting that the exceptional strength is a consequence of superposition of IA El Niño events, a warming phase of DID ENSO-like variability, and possibly an ENSO-like warming trend.     

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。     

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.     

Interannual and interdecadal variability of ocean temperature along the equatorial Pacific in conjunction with ENSO

In this paper, the leading modes of ocean temperature anomalies (OTA) along the equatorial Pacific Ocean are analyzed and their connection with El Niño-Southern Oscillation (ENSO) and interdecadal variation is investigated. The first two leading modes of OTA are connected with the different phases of the canonical ENSO and display asymmetric features of ENSO evolution. The third leading mode depicts a tripole pattern with opposite variation of OTA above the thermocline in the central Pacific to that along the thermocline in the eastern and western Pacific. This mode is found to be associated with so-called ENSO-Modoki. Insignificant correlations of this mode with the first two leading modes suggest that ENSO-Modoki may be a mode that is independent to the canonical ENSO and also has longer time scales compared with the canonical ENSO. The fourth mode reflects a warming (cooling) tendency above (below) the thermocline since 2000. Both the first and second modes have a large contribution to the interdecadal change in thermocline during 1979–2012. Also, the analysis also documents that both ENSO and OTA shifted into higher frequency since 2000 compared with that during 1979–1999. Interestingly, the ENSO-Modoki related OTA mode does not have any trend or significant interdecadal shift during 1979–2012. In addition, it is shown that first four EOF modes seem robust before and after 1999/2000, suggesting that the interdecadal shift of the climate system in the tropical Pacific is mainly a frequency shift and the changes in spatial pattern are relatively small, although the mean states over two periods experienced some significant changes.     

加利福尼亚附近的海温强迫及其与北太平洋年代际振荡的可能联系

本文利用1958～2018年期间海表面温度（SST）异常和湍流热通量异常变化的关系,探讨了其与北太平洋年代际振荡（PDO）相关的年际和年代际时间尺度上在不同海域的海气相互作用特征。结果表明:在年际尺度上,黑潮—亲潮延伸区（KOE）表现为显著大气强迫海洋,赤道中东太平洋表现为显著海洋强迫大气;在年代际尺度上,PDO北中心表现为大气强迫海洋,加利福尼亚附近则表现为显著海洋强迫大气。进一步分析表明:加利福尼亚附近区域是北太平洋准12年振荡的关键区域之一,与PDO准十年的周期类似,加利福尼亚附近的冷（暖）海温对应其上有反气旋（气旋）型环流,赤道中太平洋海水上翻和北太平洋东部副热带区域经向风应力的变化是北太平洋准12年振荡的另外两个重要环节。     

Impacts of the central and eastern Pacific types of ENSOon sea surface temperature in the South Pacific

The present study examines the relationship between two types of El Niño–Southern Oscillation (ENSO), the central Pacific (CP) ENSO and the eastern Pacific (EP) ENSO, and the sea surface temperature (SST) variability over the South Pacific (SP) (20° S–60° S, 145° E–70° W) using NOAA OI SST for the period 1982–2006. The SP SST variability associated with the two types of ENSO varies with season. These two types of ENSO can excite different atmospheric patterns associated with the Pacific–South American mode, through which they influence the SP SST variability. Both the surface turbulent air–sea heat fluxes and the heat advection by Ekman currents (i.e., Ekman heat fluxes) have an important impact on the SST variability. An analysis of the surface mixed layer heat budget indicates that the heat fluxes (the sum of turbulent heat fluxes and Ekman heat fluxes) can effectively explain much of the SST variability related to the two types of ENSO.