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1.
利用1961-2011年NCEP/NCAR再分析资料和黄河流域54站降水资料,通过讨论印度洋偶极子IOD独立发生时及IOD与ENSO联合发生时黄河流域秋季降水的差异,研究了秋季降水及环流对ENSO和IOD的响应情况.结果表明:1)仅有IOD发生时,其正位相年使得黄河流域的秋季降水相应为正异常.2)当IOD与ENSO伴随出现时,无论IOD是正位相年还是负位相年,只要和El Nino同时发生,黄河流域秋季降水都表现为负异常;和La Ni-na同时发生时,黄河流域秋季降水都表现为正异常.有无ENSO发生,IOD与秋季降水的关系有很大差异.3)欧亚中纬度地区500 hPa高度东高西低距平场形势和850 hPa黄河流域中下游南风距平异常,是黄河流域秋季降水正异常的主要环流成因.4)依据秋季海温与夏季海温相关性,可以把夏季ENSO和IOD异常信号特征作为先兆信号之一来预测秋季降水趋势. 相似文献
2.
利用3种百年时间尺度的海温资料,探讨了印度洋偶极子(India Ocean Dipole,IOD)向海盆一致模(Indian Ocean Basin,IOB)年际转变的年代际变化,结果发现1940—1970年几乎不存在这一转变现象,1970年以后该现象则十分显著。研究表明,IOD与ENSO之间海气耦合作用的年代际变化是这一转变现象的主要原因,1940—1970年IOD与ENSO之间发生发展相互独立,而1970年以后联系密切。通过进一步对物理量场的诊断分析,揭示了其中主要的动力机理:1970年以前,热带印度洋上空形成的季风环流异常无法与热带太平洋的沃克环流异常进行耦合,IOD事件发生时无法与热带太平洋产生联系。反之,1970年以后,热带两大洋上空两个纬圈环流异常之间耦合作用强烈,正(负) IOD事件发生时,通过海气相互作用,促进El Niño (La Niña)发展,印度洋又会受到来自ENSO的正反馈作用。因此这种“齿轮式”耦合模型能一直持续到冬季和次年春季,热带印度洋上空持续受到东(西)风异常的影响和低层环流的引导,西印度洋有次表层暖水的流入(出),加上印度洋本身海盆尺度较小,西边的暖(冷)水区显著增大,东西海温异常差异迅速减小并向海盆一致变暖(冷)转变,导致了后期冬季、春季正(负) IOB事件的出现。 相似文献
3.
ENSO背景下印度洋偶极子海温异常对中国冬季降水的影响 总被引：4，自引：1，他引：3
利用1950—2009年Hadley环流中心全球月平均海表温度资料、1960—2009年NCEP/NCAR再分析资料以及中国气象局整编的160站降水资料,研究分析了印度洋偶极子(IOD)和太平洋异常海温(ENSO)对中国冬季降水的协同影响和不同作用,通过对比分析,揭示了IOD独立发生、ENSO独立发生以及IOD与ENSO联合发生时中国冬季降水的差异。研究结果表明: IOD异常海温和ENSO异常海温的出现虽然具有较高的协同性,但二者对我国冬季降水的影响效应不尽相同,IOD与ENSO的同时发生并不是两者单独发生时各自作用的叠加,而是具有协同或抵消作用。仅有IOD发生时,其正位相年使得中国西南(云南西部除外)、华南以及华北、东北地区的冬季降水出现正异常,在江淮流域出现负异常,反之亦然。但是IOD正位相比负位相对中国冬季降水的影响更显著。当IOD与ENSO同时出现时,IOD的作用使得ENSO对我国西南(云南西部除外)、内蒙、东北地区冬季降水的影响作用更为显著。此外还初步分析了IOD与中国冬季降水关系影响的环流成因。 相似文献
4.
强弱南海夏季风年水汽输送路径特征分析 总被引：4，自引：1，他引：3
采用印度洋偶极子指数（dipole mode index,简称DMI）、Nino3指数和国内学者定义的5种东亚夏季风指数来比较分析印度洋偶极子（Indian Ocean dipole,简称IOD）、ENSO与东亚夏季风年际变化联系的年代际改变,讨论了这种改变的可能成因。结果表明,东亚夏季风指数分别与DMI、Ni-no3指数的年际变化的联系都呈明显的年代际改变。东亚夏季风指数除了在20世纪80年代及90年代初期与DMI联系较弱之外,其余时段均与DMI具有很好的正相关关系。当季风指数与DMI为正相关时,其与Nino3指数则呈负相关,IOD和ENSO对夏季风具有相反的影响。当季风指数与DMI呈较强的正相关时,其与ENSO的相关较弱;而在70年代末至80年代初季风指数与ENSO呈较强的相关时,其与DMI的关系亦较弱。东亚夏季风与IOD、ENSO年际变化之间的联系呈现此强彼弱的特点。1972—1982年和1983—1993年这两个阶段海温分布的显著不同,可能导致了海气相互作用过程中环流变化的周期及分布的改变,使得东亚夏季风与IOD和ENSO的关系发生年代际改变。 相似文献
5.
海洋盐度变化为研究气候变化的机制提供了一个新的视角。本文通过对比1997/1998年、2015/2016年两次强厄尔尼诺（El Ni?o）事件和2014/2015年特殊El Ni?o事件,对盐度变化及其影响海表面温度异常（SSTA）的物理过程进行了比较分析。研究表明,El Ni?o和南方涛动（El Ni?o–Southern Oscillation, ENSO）发展的强弱与热带西太平洋大范围海表层盐度异常（SSSA）及其向东扩散的差异有明显关联。1997/1998、2015/2016年赤道东太平洋SSTA的增暖,对应两次强El Ni?o事件,在发生年4月,中西太平洋海域出现了明显的负SSSA,之后东移至日期变更线以西,SSSA引发的混合层深度（MLD）变浅、障碍层厚度（BLT）变厚,导致热带中—西太平洋表层升温增强,促使了赤道中太平洋的早期变暖;2014/2015年弱El Ni?o事件虽然在发生年4月,位于赤道中西太平洋出现了负SSSA,但没有发展东移,导致BLT的增厚过程减弱,对表层温度的调制作用减弱甚至消失。三次事件对应的盐度变化过程中,水平平流和淡水通量（FWF）引起的表层强迫是影响盐度收支的主要因子,水平平流影响盐度异常的前期变化,触发事件的发生;热带太平洋西部降水引起的FWF负异常的影响最为显著,对ENSO异常信号出现后SSSA的维持起决定性作用。相比较两次强El Ni?o事件,2014/2015年El Ni?o对应的早期FWF负异常没有发展和东移,并且之后迅速减弱,导致中西太平洋盐度负趋势减缓,MLD加深,BLT变薄,促使上表层海水冷却,抑制了赤道东太平洋的早期变暖和ENSO发展。研究结果表明,盐度变化与ENSO密切相关,热带中西太平洋海域早期表层盐度变化可能可以作为SSTA的指数。特别地,SSSA在调节SSTA时,不仅影响它的强度,而且可以作为判断ENSO是否发展及其强弱的前兆因子。 相似文献
6.
利用逐月OISST、ERSST及NCEP2表面风场等资料探讨了南印度洋偶极子(Southern Indian Ocean Dipole,SIOD)的结构特征、形成原因及其与ENSO的关系。结果表明:在南印度洋,偶极子形态的年际海表面温度异常在10—12月出现,次年2月达到极值,随后的4—6月消亡。SIOD的形成主要是风场、潜热通量和短波辐射通量起作用,混合层深度异常加厚或变浅有助于SIOD的形成。近30 a资料表明,SIOD的盛期超前ENSO 9~10个月,且具有季节锁相特征。20世纪70年代中期发生年代际气候突变后,SIOD与ENSO的相关关系显著增强。正SIOD事件之后一般都有El Nio事件发生,负SIOD事件之后都有La Nia事件发生。 相似文献
7.
ENSO对印度洋偶极子与中国秋季降水关系的影响 总被引：14，自引：3，他引：14
利用1950--1999年Hadley中心全球海温资料、NCEP／NCAR再分析资料和中国气象局整编的160站降水资料，通过讨论印度洋偶极子（IOD）独立发生时及IOD与ENSO联合发生时中国秋季降水的差异，研究了ENSO对IOD与中国秋季降水关系的影响。结果表明：仅有IOD发生时，其正位相年使得中国西南地区和黄河流域的秋季降水出现正异常，而当IOD与ENSO伴随出现时，IOD正位相年和E1Nino使得中国西南地区秋季降水正异常区域维持并向东扩展，还使得黄河流域秋季降水转为负异常。此外分析了ENSO改变IOD与中国秋季降水关系的环流成因。 相似文献
8.
本文基于动力调整方法,利用客观分析海气通量（OAFlux）资料研究了1958～2016年全球海洋蒸发量变化及其动力作用和辐射强迫分量的变化,发现海洋蒸发量及其动力作用分量具有一致性年代际变化特征,特别是在20世纪70年代及90年代末期存在明显的年代际转折。进一步分析发现:主要动力因子有太平洋—北美遥相关型（PNA）、北极涛动（AO）、北大西洋涛动（NAO）、厄尔尼诺—南方涛动（ENSO）和阿留申低压（AL）,并受到太平洋年代际振荡（PDO）的影响,其中,1970年代末期的转折与PNA、PDO、ENSO和AL密切相关,而1990年代末期的转折还与NAO变化有关。动力作用分量的前六个模态解释方差达到67.5%,其中,低纬北太平洋和印度洋蒸发异常主要与海表温度（SST）及其引起的环流异常有关,南太平洋、中纬北太平洋和北大西洋蒸发异常与环流异常直接相关。ENSO与PDO在全球海洋蒸发量上的影响要大于NAO。单因子相关分析发现南方涛动指数（SOI）、NAO和PDO与海洋蒸发年代际变化密切相关。总体来说,动力作用分量在海洋蒸发的年代际变化中起主导作用,其中,以ENSO、NAO和PDO的影响最大。 相似文献
9.
ENSO空间形态变异对ENSO-IOD关系年代际减弱的可能作用 总被引：1，自引：0，他引：1
基于1979—2017年哈得来中心的逐月海表温度资料（HadISST）和美国环境预报中心/美国大气研究中心（NCEP/NCAR）提供的大气环流再分析数据,研究了北半球秋季厄尔尼诺和南方涛动（ENSO）与印度洋偶极子（IOD）关系的年代际变化特征及其可能原因。结果显示,ENSO-IOD关系存在显著的年代际变化:21世纪初期前,二者呈显著正相关,厄尔尼诺（拉尼娜）年秋季常对应显著的印度洋偶极子正（负）异常;21世纪初期以后,ENSO-IOD关系显著减弱,统计上不显著。进一步研究表明,ENSO空间型态的变异对于该关系的年代际减弱起重要作用。在第二时段（2004—2017年）,中部型厄尔尼诺事件和东部型拉尼娜事件频发,中部型厄尔尼诺事件与印度洋偶极子强度的关系与其纬向位置密切相关,与其强度的线性关系较弱;而东部型拉尼娜事件,由于海温距平位置偏东（位于赤道东太平洋冷舌区）,在偏低的气候态海温作用下,其引起的大气局地响应很弱,对印度洋的遥强迫作用较弱,因而对印度洋偶极子强度的影响也较弱。在二者的共同作用下,ENSO-IOD的关系发生了年代际减弱。 相似文献
10.
平流层极涡振荡与ENSO热带海温异常的时空联系 总被引：6，自引：3，他引：3
利用一个在等熵位涡坐标下建立的平流层极涡振荡(Polar Vortex Oscillation)指数,以及NCEP/NCAR再分析资料和NOAA_OISST_V2逐周海温资料,研究了月尺度以上热带海温异常与平流层极涡振荡的时间和空间联系,通过相关、回归以及合成分析发现,两者的显著联系主要发生在3—5年的年际时间尺度上,表现为ENSO型海温异常与极涡振荡年际趋势之间的时空关联。首先,两者的关系并不表现在同期相关上,而是当ENSO海温异常超前极涡振荡年际异常9—11个月时,两者具有最大的负相关关系。当前期热带海温偏暖(冷)时,9—11个月后极涡振荡的年际趋势为负(正)的异常,即极涡偏弱(强)或负(正)振荡事件为主。统计合成结果进一步证实,前期热带ENSO海温暖事件背景下,后期极涡振荡负事件的发生比正事件更多,强度更强,持续时间也更长,反之亦然;另外,前期热带ENSO暖海温背景下,极涡正、负振荡事件的发生均更频繁。研究连接热带ENSO海温异常与平流层极涡振荡的过程发现,热带海温异常不仅可在热带地区引起大气温度的异常响应,而且可以引发从平流层热带到极区的一系列温度异常同时向下和向极区的传播过程,并与9—11个月以后发生在极区的极涡振荡异常相联系。表明与热带海温异常相联系的极涡振荡年际异常,可能存在与季节尺度极涡振荡中类似的全球质量环流的异常变化。 相似文献
11.
Indian Ocean sea surface salinity variations in a coupled model 总被引：2，自引：0，他引：2
The variability of the sea surface salinity (SSS) in the Indian Ocean is studied using a 100-year control simulation of the Community Climate System Model (CCSM 2.0). The monsoon-driven seasonal SSS pattern in the Indian Ocean, marked by low salinity in the east and high salinity in the west, is captured by the model. The model overestimates runoff into the Bay of Bengal due to higher rainfall over the Himalayan–Tibetan regions which drain into the Bay of Bengal through Ganga–Brahmaputra rivers. The outflow of low-salinity water from the Bay of Bengal is too strong in the model. Consequently, the model Indian Ocean SSS is about 1 less than that seen in the climatology. The seasonal Indian Ocean salt balance obtained from the model is consistent with the analysis from climatological data sets. During summer, the large freshwater input into the Bay of Bengal and its redistribution decide the spatial pattern of salinity tendency. During winter, horizontal advection is the dominant contributor to the tendency term. The interannual variability of the SSS in the Indian Ocean is about five times larger than that in coupled model simulations of the North Atlantic Ocean. Regions of large interannual standard deviations are located near river mouths in the Bay of Bengal and in the eastern equatorial Indian Ocean. Both freshwater input into the ocean and advection of this anomalous flux are responsible for the generation of these anomalies. The model simulates 20 significant Indian Ocean Dipole (IOD) events and during IOD years large salinity anomalies appear in the equatorial Indian Ocean. The anomalies exist as two zonal bands: negative salinity anomalies to the north of the equator and positive to the south. The SSS anomalies for the years in which IOD is not present and for ENSO years are much weaker than during IOD years. Significant interannual SSS anomalies appear in the Indian Ocean only during IOD years. 相似文献
12.
The Equatorial Undercurrent in the central Atlantic and its relation to tropical Atlantic variability 总被引：1，自引：0，他引：1
Peter Brandt Andreas Funk Alexis Tantet William E. Johns Jürgen Fischer 《Climate Dynamics》2014,43(11):2985-2997
Seasonal to interannual variations of the Equatorial Undercurrent (EUC) in the central Atlantic at 23°W are studied using shipboard observation taken during the period 1999–2011 as well as moored velocity time series covering the period May 2005–June 2011. The seasonal variations are dominated by an annual harmonic of the EUC transport and the EUC core depth (both at maximum during September), and a semiannual harmonic of the EUC core velocity (maximum during April and September). Substantial interannual variability during the period of moored observation included anomalous cold/warm equatorial Atlantic cold tongue events during 2005/2008. The easterly winds in the western equatorial Atlantic during boreal spring that represent the preconditioning of cold/warm events were strong/weak during 2005/2008 and associated with strong/weak boreal summer EUC transport. The anomalous year 2009 was instead associated with weak preconditioning and smallest EUC transport on record from January to July, but during August coldest SST anomalies in the eastern equatorial Atlantic were observed. The interannual variations of the EUC are discussed with respect to recently described variability of the tropical Atlantic Ocean. 相似文献
13.
Assessment of interannual sea surface salinity variability and its effects on the barrier layer in the equatorial Pacific using BNU-ESM 总被引：1，自引：0，他引：1
As salinity stratification is necessary to form the barrier layer (BL), the quantification of its role in BL interannual variability is crucial. This study assessed salinity variability and its effect on the BL in the equatorial Pacific using outputs from Beijing Normal University Earth System Model (BNU-ESM) simulations. A comparison between observations and the BNU-ESM simulations demonstrated that BNU-ESM has good capability in reproducing most of the interannual features observed in nature. Despite some discrepancies in both magnitude and location of the interannual variability centers, the displacements of sea surface salinity (SSS), barrier layer thickness (BLT), and SST simulated by BNU-ESM in the equatorial Pacific are realistic. During El Niño, for example, the modeled interannual anomalies of BLT, mixed layer depth, and isothermal layer depth, exhibit good correspondence with observations, including the development and decay of El Niño in the central Pacific, whereas the intensity of the interannual variabilities is weaker relative to observations. Due to the bias in salinity simulations, the SSS front extends farther west along the equator, whereas BLT variability is weaker in the central Pacific than in observations. Further, the BNU-ESM simulations were examined to assess the relative effects of salinity and temperature variability on BLT. Consistent with previous observation-based analyses, the interannual salinity variability can make a significant contribution to BLT relative to temperature in the western-central equatorial Pacific. 相似文献
14.
基于美国国家航天局（NASA）发射的水瓶座（Aquarius/SAC-D）卫星和欧洲航天局（ERA）发射的土壤湿度与海洋盐度（SMOS）卫星的观测资料,以及Argo海表盐度资料,重点分析了阿拉伯海中北部海表盐度的季节和年际变化.年平均情况下,Argo、Aquarius和SMOS表现出相似的海表盐度分布形态,均表现了阿拉伯海中北部高达36.5 psu的高盐特征.阿拉伯海中北部海表盐度在2—3月出现最低值,在4月之后快速升高,并在夏季西南季风的成熟阶段达到最高.阿拉伯海中北部海表盐度显著的季节变化与季风风场引起的大量蒸发和平流输送相关.夏季风期间,Ras al Hadd急流将来自阿曼湾的高盐水向东向南输送到阿拉伯海中北部海域,使海表盐度升高并达到最高值;冬季风期间,冬季风环流系统在印度半岛西侧海域形成向北的低盐水输送,造成阿拉伯海中北部海表盐度降低.该低盐水平流在冬季风后期能够影响到阿曼海.阿拉伯海中北部海表盐度年际变化主要与季风驱动的季风环流系统的变化相关,尤其是冬季风期间向北流动的印度西侧沿岸流的强弱与该区域海表盐度年际变化关系密切. 相似文献
15.
Distinguished Effects of Interannual Salinity Variability on the Development of the Central-Pacific El Nino Events 
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下载免费PDF全文 El Nio events in the central equatorial Pacific (CP) are gaining increased attention,due to their increasing intensity within the global warming context.Various physical processes have been identified in the climate system that can be responsible for the modulation of El Nio,especially the effects of interannual salinity variability.In this work,a comprehensive data analysis is performed to illustrate the effects of interannual salinity variability using surface and subsurface salinity fields from the Met Office ENSEMBLES (EN3) quality controlled ocean dataset.It is demonstrated that during the developing phase of an El Nio event,a negative sea surface salinity (SSS) anomaly in the western-central basin acts to freshen the mixed layer (ML),decrease oceanic density in the upper ocean,and stabilize the upper layers.These related oceanic processes tend to reduce the vertical mixing and entrainment of subsurface water at the base of the ML,which further enhances the warm sea surface temperature (SST) anomalies associated with the El Nio event.However,the effects of interannually variable salinity are much more significant during the CP-El Nio than during the eastern Pacific (EP) El Nio,indicating that the salinity effect might be an important contributor to the development of CP-El Nio events. 相似文献
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Effects of interannual salinity variability on the barrier layer in the western-central equatorial Pacific: A diagnostic analysis from Argo 总被引：4，自引：0，他引：4
ABSTRACT In this paper, interannual variations in the barrier layer thickness （BLT） are analyzed using Argo three-dimensional temperature and salinity data, with a locus on the effects of interannually varying salinity on the evolution of the El Nifio Southern Oscillation （ENSO）. The interannually varying BLT exhibits a zonal seesaw pattern across the equatorial Pacific during ENSO cycles. This phenomenon has been attributed to two different physical processes. During E1 Nifio （La Nifia）, the barrier layer （BL） is anomalously thin （thick） west of about 160°E, and thick （thin） to the east. In the western equatorial Pacific （the western part： 130°-160°E）, interannual variations of the BLT indicate a lead of one year relative to those of the ENSO onset. The interannual variations of the BLT can be largely attributed to the interannual temperature variability, through its dominant effect on the isothermal layer depth （ILD）. However, in the central equatorial Pacific （the eastern part： 160~E- 170~W）, interannual variations of the BL almost synchronously vary with ENSO, with a lead of about two months relative to those of the local SST. In this region, the interannual variations of the BL are significantly affected by the interannually varying salinity, mainly through its modulation effect on the mixed layer depth （MLD）. As evaluated by a onedimensional boundary layer ocean model, the BL around the dateline induced by interannual salinity anomalies can significantly affect the temperature fields in the upper ocean, indicating a positive feedback that acts to enhance ENSO. 相似文献
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使用江西省82站1959—2016年6月降水资料和NCEP/NCAR逐月再分析资料,研究了南印度洋大气垂直环流与江西6月降水的关系,并运用大尺度局地涡度倾向变化方程诊断了年际、年代际变化引起的局地涡度倾向异常对江西6月降水的贡献,解释了南印度洋大气垂直环流与江西6月降水年际关系发生年代际改变的原因。结果表明南印度洋大气垂直环流与江西6月降水有密切的关系,且两者的年际关系存在年代际变化:（1）二者关系在1960年代末和1990年代初发生了两次转变,1969年前为显著正相关,1969—1989年相关性不明显,1990年后又转变为显著正相关。（2）江西6月降水偏多年,500 hPa上东亚地区从中高纬到低纬为“+ - +”距平符号分布,江西区域异常正涡度,低层南北风距平在江西上空交汇;降水偏少年环流异常则相反。（3）南印度洋大气垂直环流可引起东亚环流异常,使江西区域涡度正异常;但其影响与背景场的变化有关。动力诊断表明,1969—1989年南印度洋大气垂直环流年际异常对江西局地涡度为正贡献,但年代际异常为负贡献,削弱了年际异常的作用;1990—2016年阶段年际异常为正贡献,同时年代际异常也为正贡献,加强了年际异常的作用,使得其与江西6月降水的正相关显著。 相似文献
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Wei Zhou Mengyan Chen Wei Zhuang Fanghua Xu Fei Zheng Tongwen Wu Xin Wang 《大气科学进展》2016,33(2):208-220
The second-generation Global Ocean Data Assimilation System of the Beijing Climate Center(BCC_GODAS2.0) has been run daily in a pre-operational mode.It spans the period 1990 to the present day.The goal of this paper is to introduce the main components and to evaluate BCC_GODAS2.0 for the user community.BCC_GODAS2.0 consists of an observational data preprocess,ocean data quality control system,a three-dimensional variational(3DVAR) data assimilation,and global ocean circulation model[Modular Ocean Model 4(MOM4)].MOM4 is driven by six-hourly fluxes from the National Centers for Environmental Prediction.Satellite altimetry data,SST,and in-situ temperature and salinity data are assimilated in real time.The monthly results from the BCC_GODAS2.0 reanalysis are compared and assessed with observations for 1990-2011.The climatology of the mixed layer depth of BCC-GODAS2.0 is generally in agreement with that of World Ocean Atlas 2001.The modeled sea level variations in the tropical Pacific are consistent with observations from satellite altimetry on interannual to decadal time scales.Performances in predicting variations in the SST using BCC_GODAS2.0 are evaluated.The standard deviation of the SST in BCC-GODAS2.0 agrees well with observations in the tropical Pacific.BCC-GODAS2.0 is able to capture the main features of E1 Nino Modoki I and Modoki Ⅱ,which have different impacts on rainfall in southern China.In addition,the relationships between the Indian Ocean and the two types of E1 Nino Modoki are also reproduced. 相似文献
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分析了从GTS(全球无线通讯系统)获得的2002-2007年海洋温盐观测资料在国家气候中心第2代全球海洋资料同化系统(BCC_GODAS 2.0)中的同化结果。与SODA(简易海洋同化数据)资料的比较表明:GTS中的海洋温盐资料同化对模式温盐场的改进之处主要表现在混合层暖区的范围和中心强度、温跃层中温度槽脊的深度、温跃层附近的温度梯度以及盐度高、低值区的范围和中心强度等方面,同化后全球温盐场的均方根误差得到一定程度的降低。挑选位于不同海区的单点温盐廓线与ARGO(地转海洋学实时观测阵)观测作了进一步比较,结果表明:大多数情况下,同化后温盐廓线的均方根误差得到明显降低,模拟的温盐垂向分布特征也更为准确。与TAO(热带大气海洋观测网)资料的比较也同样表明:同化后的温盐场特征会得到一定程度改善。 相似文献
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In this study, statistical techniques are employed to decompose climate signals around southern Africa into the dominant temporal frequencies, with the aim of modelling and predicting area-averaged rainfall. In the rainfall time series over the period 1900–1999, the annual cycle accounts for 83% of variance. Residual spectral energy cascades from biennial (42%) to interannual (20%) to decadal bands (3%). Regional climate signals are revealed through a multi-taper singular value decomposition analysis of sea surface temperature and sea level pressure fields over the Atlantic and Indian Oceans, in conjunction with southern Africa rainfall. Rossby wave action in the South Indian Ocean dominates the biennial scale variability. El Niño-Southern Oscillation (ENSO) and related Indian Ocean dipole patterns are important for interannual variability. Significant sea temperature and pressure fluctuations occurring 6–12 months prior to rainfall contribute biennial and interannual indices to a multi-variate model that demonstrates useful predictive skill. 相似文献