【作者】 王鑫；

【导师】 李崇银；

【作者基本信息】 中国科学院研究生院（大气物理研究所） ， 气象学， 2007， 博士

【摘要】 本文利用观测资料以及IPCC数值模拟结果,分析了副热带太平洋的年代际变化。结果表明,对于年代际尺度,表层海温在副热带北太平洋东部最显著,尤其是在夏秋季,并且其上空的大气场也有明显的年代际信号。通过SVD分析,发现副热带北太平洋表层海温的年代际变化与大气动量强迫有关,而受潜热、感热、淡水强迫影响较小;并且较少受热带太平洋遥相关的影响。本文的研究首次提出副热带北太平洋东部海温异常在PDO的演变过程中有重要的作用,副热带北太平洋地区的海温异常可以传播到热带太平洋,然后通过黑潮及其延伸体将该异常传播到北太平洋中纬地区,最终引起PDO位相的转变。利用IPCC AR4四个耦合模式的模拟结果,进一步证实副热带北太平洋东部海温存在显著的年代际信号,并且验证了其观测资料统计分析中的各种特征。研究也发现这些耦合模式很难模拟出副热带北太平洋大气的年代际变化。副热带南太平洋的表层海温和海平面气压场也存在着显著的年代际信号,南太平洋海温年代际变化在北半球冬季(DJF)最显著。海温年代际信号最早出现在副热带南太平洋东南,然后经过8年左右的时间可以传播到南太平洋的西边界-澳大利亚的东北部,并且最终会穿越赤道,到达北半球。本文的结果还证明了副热带南太平洋海温年代际变化与热带太平洋的年际变化有密切的关系。副热带北太平洋东部海温和梅雨的关系在年代际尺度上最显著,它通过影响热带太平洋地区低层风场和海温的变化,影响梅雨降水。观测和数值模拟都表明梅雨降水的变化还受南印度洋海温偶极子变化的影响,当海温偶极子模态为正位相时,梅雨降水偏多,反之偏少。本文还研究了ENSO时对梅雨影响的不对称特性,尤其是La Nia与次年梅雨降水关系的年代际变化,在1976/77气候漂移之前/后,La Nia一般会造成梅雨降水偏多/少。70年代末期热带太平洋海温基本态的变化,是导致1976年前后La Nia事件和梅雨关系变化的主要原因。本文还分析了印度洋不同海区(阿拉伯海、赤道印度洋和南印度洋)、热带东太平洋海温异常与印度夏季风降水的关系,研究表明不同的海区在不同时期对印度降水的影响也不同,他们的相关关系有明显的年代际变化特征。更多还原

【Abstract】 Using the observed datasets and the four models results of IPCC AR4 20C3M, the paper studied the interdecadal variations in the subtropical Pacific. It was found that the interdecadal SST variations over eastern subtropical North Pacific are more significant than other regions of North Pacific, and are significant only during boreal summer and autumn. Besides interdecadal SSTs variations, the interdecadal atmospheric variations over the Subtropical North Pacific are significant. The study also examined the possible causes leading to interdecadal SST variations in the Subtropical North Pacific. Applied with SVD analysis, the momentum flux plays more important roles than freshwater flux, latent heat, and sensible heat flux in maintaining the interdecadal SST variations. Furthermore, the analyses suggested that the local atmospheric forcing, other than tropical teleconnection forcing from the tropics, results in the SST interdecadal variations in the Subtropical North Pacific. The paper firstly pointed out the roles of interdecadal SST variations in the subtropical North Pacific on PDO evolution. The subtropical SST anomalies could propagate tropical Pacific. The further results showed that the SST anomaly in the Subtropical North Pacific region would reach tropical Pacific, and be taken to midlatitude Pacific by Kuroshio Current, and finally changes original SST anomaly signal in the midlatitude Pacific, thus results in the change of PDO phase. With the analysis of the four models results of IPCC AR4 20C3M, the significant interdecadal SSTA variations in the Subtropical North Pacific and its characters have been confirmed. However, the four coupled models are hardly simulating the interdecadal variation of atmosphere in the Subtropcial North Pacific.The paper also found that the SSTs and sea level pressure in the Subtropical South Pacific have the significant interdecadal variations, and the interdecadal SSTA mode is significant only during boreal winter (DJF). The interdecadal variation of SSTA firstly occurring in the subtropical South Pacific propagates to the western boundaries of the South Pacific, then moves northeast to cross the equator, and finally reaches the central tropic Pacific. It takes about 8 years to propagate from southeast subtropical Pacific to the north hemisphere. Moreover, the paper showed that the interdecadal SSTA variability originated in the subtropical southeast Pacific is related closely with interannual variability in the tropic Pacific.The paper found that the subtropical north Pacific SSTA is significant correlated with Mei-yu rainfall on the interdecadal timescales, which influences the Mei-yu rainfall variations through changing the SST and wind in the tropical Pacific. Both the observed and model results showed the impacts of SSTA dipoles in the South Indian Ocean on Mei-yu rainfall. When the SSTA dipoles are in positive phase, Mei-yu rainfall is more and vice verse.The asymmetry impacts of ENSO on Mei-yu rainfall were studied in the paper, especially the interdecadal impacts of La Ni?a on Mei-yu rainfall in next year. After La Ni?a occurs, the Mei-yu rainfall is more/less than normal level before/after 1976. Our results showed that the such changing relationship between La Ni?a and Mei-yu rainfall is due to the equatorial Pacific mean SSTs changes in 1976/77. Finally, the paper examined the relationships between summer Indian rainfall and SSTA in different areas, including the Arabian Sea, the equatorial Indian Ocean, the southern Indian Ocean and the equatorial eastern Pacific, and indicated the interdecadal variations of influences of SSTA on Indian rainfall.更多还原