Pacific coral oxygen isotope and the tropospheric temperature gradient over the Asian monsoon region: a tool to reconstruct past Indian summer monsoon rainfall

Having recognized that it is the tropospheric temperature (TT) gradient rather than the land–ocean surface temperature gradient that drives the Indian monsoon, a new mechanism of El Niño/Southern Oscillation (ENSO) monsoon teleconnection has been unveiled in which the ENSO influences the Indian monsoon by modifying the TT gradient over the region. Here we show that equatorial Pacific coralline oxygen isotopes reflect TT gradient variability over the Indian monsoon region and are strongly correlated to monsoon precipitation as well as to the length of the rainy season. Using these relationships we have been able to reconstruct past Indian monsoon rainfall variability of the first half of the 20th century in agreement with the instrumental record. Additionally, an older coral oxygen isotope record has been used to reconstruct seasonally resolved summer monsoon rainfall variability of the latter half of the 17th century, indicating that the average annual rainfall during this period was similar to that during the 20th century. Copyright © 2011 John Wiley & Sons, Ltd.     

The relationship between the canonical ENSO and the phase transition of the Antarctic oscillation at the quasi-quadrennial timescale

A correlation analysis is performed to investigate the relationship between El Nino-Southern Oscillation (ENSO) and the Antarctic oscillation (AAO) at the quasi-quadrennial (QQ) timescale.It is found that the cold tongue index (CTI) and the AAO index (AAOI) are negatively correlated with about a 7-month lead-time,while they are positively correlated with about a 15-month lag-time.To further explore this relationship,complex empirical orthogonal function analysis is employed in the QQ sea level pressure (SLP) anomalies from 1951 to 2002.The results indicate that,during the ENSO cycle,there exists one kind of global tropical wave of wavenumber 1 (GTW1) propagating eastward.With the traveling of GTW1,the tropical SLP anomaly tends to intrude into the southern mid-latitudes.Accordingly,three strong signals travel synchronously along the circumSouth-Pacific path,and a relatively weak signal extends eastward and poleward over the South Ocean in the Atlantic-Indian Ocean sector.Following the propagation of these signals,the AAO phase tends to be reversed progressively.As a result,there exists an evident lead-lag correlation between CTI and AAOI.It can be concluded that ENSO plays a key role in the phase transition of AAO at the QQ timescale.It is also noticed that this regular relationship is only evident in the canonical ENSO events,for which sea surface temperature (SST) anomalies extend westward from the tropical eastern Pacific.On the other hand,the similar relationships are not found among those atypical ENSO events for which SST anomalies spread eastward from the central Pacific,such as the 1982-1983 ENSO event.     

近40年中国区域的气候型变化与北半球大气环流特征10年际时空变化的关系

根据１８００－１９８９年（１１０年）的资料，分析研究了新加坡地区月平均和年平均降雨量的一些特征。主要结论是：新加坡年平均降雨量存在准２－６年和１８年的周期振荡；亚洲季风以及ＥＮＳＯ对新加坡降雨量有明显的影响。新加坡年雨量的谷值出现在西南季风期而峰值在东北季风期。在Ｅｌ Ｎｉｎｏ年，新加坡降雨量多为负距平；而在反Ｅｌ Ｎｉｎｏ年，新加坡降雨量多为正距平。     

1991—1992年ENSO事件的特征

根据美国国家海洋大气局气候分析中心（ＣＡＣ）和中国气象局气候监测公报所提供的海－气资料，综合分析了１９９１－１９９２年ＥＮＳＯ事件的形成、发展过程。这次ＥＮＳＯ事件的主要特点是：①在ＥＮＳＯ事件爆发前一年内热带太平洋海气特性频频呈现异常，暖水堆积在赤道中太平洋（５°Ｎ－５°Ｓ，１６０°Ｅ－１６０°Ｗ）约１２个月，然后自西向东传输，爆发１９９１－１９９２年ＥＮＳＯ事件。②对ＥＮＳＯ事件作出响应的西太     

ENSO事件发展的时空特征

本文利用1951—1988年10°S—50°N太平洋SST资料与EOF分析方法对ENSO事件的发展过程与循环的时空特征进行了分析.分析结果表明EOF第一主分量时间系数的变化可以很好地表示SST距平变化与ENSO事件的发生.并且,第一主分量空间函数分布的变化揭示了一种ENSO事件增温是春季首先始于赤道东太平洋沿岸,随后向西传播到赤道中太平洋的增温过程;而第二主分量空间函数分布的变化揭示了另一种ENSO事件可增温首先始于赤道中太平洋,然后向东传播到赤道东太平洋的增温过程.分析结果还表明,ENSO事件的强度是强弱相间,其周期平均大约为4年左右. 本文还比较了80年代热带太平洋SST的变化及所发生的两次ENSO事件与其它年代所发生的ENSO事件的差别.     

热带海气耦合距平模式中的ENSO循环及其形成机制

本文研制设计了一包含海洋表面边界层和大气辐合反馈过程的热带太平洋海气耦合异常模式。进而利用该模式对ＥＮＳＯ循环进行了成功的模拟。通过对模式ＥＮＳＯ循环的演变特征及其形成机制的细致分析，揭示了ＥＮＳＯ暖位相的一种机制。     

从时间序列中提取维数信息

作者介绍了分形和分维的概念、性质和意义，重点讨论了从一维时间序列中提取维数信息的方法，并给出了一些在天气和气候中的应用。     

DIAGNOSTIC ANALYSIS AND VERIFICATION OF PREDICTION OF THE TROPICAL PACIFIC SEA SURFACE TEMPERATURE ANOMALIES DURING 1997 ~ 1998

By comparing with ENSO events that ever happened in the history, the basic features and probable causes of the anomalous sea surface temperature of the tropical Pacific Ocean during 1997 and 1998 have been analyzed diagnostically. It is found that the 1997/1998 El Nino had significant abnormalities and peculiarities. It differs from the previous El Ni?o events falling into the simple “eastern pattern” or “western pattern”. The predictions of 1997/1998 El Ni?o event have also been tested with an intermediate ocean-atmosphere coupled dynamic model. The results show that the skills of the 0～24 lead month forecasts for the warm event are all above 0.5. The predictions of the mature phase and the later stages of the warm event are better than those of the beginning phase.     

Annual ENSO simulated in a coupled ocean–atmosphere model

Using an output from 200-year integration of the Scale Interaction Experiment of EU project-F1 model (SINTEX-F1), the annual ENSO reproduced in the coupled general circulation model is investigated, suggesting the importance of reproducing an annual cycle in realistically simulating ENSO events. Although many features of the annual ENSO are reproduced, the northward expansion of sea surface temperature anomaly (SSTA) in the eastern tropical Pacific stays south of the equator. It is suggested that this model bias is due to the excitation of the too strong Rossby waves in the southeastern tropical Pacific, which reflect at the western boundary and intrude into the eastern equatorial Pacific. The zonal wind stress anomaly along the equator also plays an important role in generating the equatorial Kelvin waves. The amplitude of SSTA for the annual ENSO mode is reproduced, but its variance is only 20% of the observation; this is again due to the lack of northward migration of seasonal SSTA in the equatorial region and weaker coastal Kelvin waves along South America. Remedies for the model bias are discussed.     

海洋对ENSO和其他时间尺度上风应力振荡的响应

利用带通滤波方法，将FSU风应力资料分离成ENSO时间尺度上的分量及其剩余部分，将这两部分分别作用于模式海洋（2层热带太平洋区域模式），研究海洋对不同时间尺度大气变化的响应。结果表明：尺管ENSO时间尺度上的风应力分量只占风应力扰动总方差的30％左右，它却能激发出全部异常风应力强迫海洋时所产生的El Nino/La Nina现象和十分相近的SSTA变化周期与振幅。而其余占总异常风应力方差60％以上的部分强迫海洋仅能产生振幅较小的海表温度异常，在非ENSO和ENSO时间尺度上的风应力强迫下，海洋中可产生相近振幅的Kelvin波，但SSTA振幅却存在显著差别，表明海洋对大气扰动信号的频率非常敏感，这里从理论上对该现象作了解释和说明。