【作者】 刘芸芸；

【导师】 丁一汇；

【作者基本信息】 中国气象科学研究院 ， 气象学， 2009， 博士

【摘要】 亚洲-太平洋季风系统是全球季风系统中最显著的一个季风系统。它所包含的各季风子系统间的相互作用对季风区甚至全球的气候变化都有非常显著的影响。本论文深入研究了亚洲-太平洋季风区中印度夏季风、东亚夏季风和西北太平洋夏季风各季风子系统之间的遥相关型,以及它们对中国东部地区夏季降水的遥相关影响。通过分析,我们得到亚洲-太平洋季风区的4种遥相关关系,它们清楚地显示了印度夏季风、东亚夏季风和西北太平洋夏季风之间的相互作用,但它们在不同的时间和空间上表现出完全不同的联系。这表明,印度夏季风、西北太平洋夏季风和东亚夏季风在建立、推进过程以及结构特征方面,既存在显著的独立性,但它们却又在一定程度上表现出非常紧密的联系。在给出每种遥相关关系的同时,也从大气环流、水汽输送及数值模拟等方面很好地解释了每种遥相关关系存在的原因。最后,我们从整体的角度,用风场、水汽输送和降水表现了亚洲-太平洋夏季风整体一致的年际变化特征,这为亚洲夏季风降水的预报工作提供了更多的参考依据。主要结论概括如下:(1)在夏季风爆发初期,印度夏季风的爆发与中国长江流域梅雨的开始存在相差大约两周的对应关系,并形成从印度西南部经孟加拉湾到达中国长江流域及日本南部的遥相关型,即“南支”遥相关型。在这两周里,亚洲季风环流发生了一系列重要变化:印度夏季风爆发、南亚高压北进、中层爆发性涡旋生成、低层热带西风带不断加强东传及西太平洋副高北跳东退。结果,在东亚地区上空形成相互耦合的高、低空西风急流,长江流域正好位于高、低空急流之间,高空急流入口区右侧和低空急流左侧的上升运动区,因此触发了长江流域梅雨的发生。(2)在夏季风盛行期,长江流域的降水异常更多的是受西北太平洋夏季风的影响,与西北太平洋的西南季风降水呈反相关关系。从气候平均的季节内尺度分析则发现,由于季风减弱的年份,长江流域受到源自印度洋的东传CISO和源自西北太平洋的西传CISO的共同影响,可能形成某种锁相关系,从而造成长江流域降水偏多。(3)与长江流域相反,我国华北汛期降水异常则与西北太平洋东南季风呈正相关关系,异常强的偏东气流所携带的水汽输送对华北汛期降水异常有重要的影响。从季节内尺度分析,华北汛期降水偏多是由于受到源自热带西太平洋的北传CISO和来自高纬度地区的南传CISO的共同影响。(4)华北夏季降水同时还与印度夏季风呈正相关关系,在夏季风盛行期,形成由印度西北部经青藏高原到我国华北地区的西南-东北走向的遥相关型,即“北支”遥相关型。这是由于印度季风的强度主要受印度低压的影响,当印度低压加深的同时,中高纬低压槽也加深发展,西北太平洋高压脊西伸北跳,从而有利于华北地区降水偏多。(5)亚洲-太平洋夏季风在年际尺度上具有一致的变化特征,表现为2～3年的振荡周期。也就是说,当亚洲夏季风中某一季风子系统表现为异常偏强时,其他季风子系统在这一年中也都将表现为异常偏强,反之亦然。其中以水汽输送表征的夏季风,其一致的年际变化特征更为显著。准两年的振荡周期可能是亚洲-太平洋夏季风系统的一种固有振荡,它与暖洋面上的海气相互作用振荡有密切关联。更多还原

【Abstract】 The interactions among the Asian-Pacific monsoon subsystems have significant impacts on the climatic regimes in the monsoon region and even the whole world.The teleconnections of the Indian summer monsoon（ISM）,the East Asian summer monsoon （EASM） and the western North Pacific summer monsoon（WNPSM）,the subsystems of the Asian-Pacific summer monsoon,in the Asian-Pacific monsoon region,and their associations with the summer precipitation in China are studied in this paper.The ISM,EASM and WNPSM are significantly independent in the date of onset,the northward advancing march and their structures,but also they are closely linked with each other to some extent.Four different teleconnection modes are found in the Asian-Pacific monsoon region,which reveal clearly the interactions among the ISM,EASM and WNPSM,in different space and time.On the other hand,we also explain the reasons for the existence of each teleconnection from the aspects of atmospheric circulation,water vapor transport and numerical simulation,etc. Finally,the consistent interannual variation of the Asian-Pacific monsoon is performed through 850hPa wind,water vapor transport and precipitation from an overall perspective, which provides more valuable reference for the Asian summer monsoon precipitation forecasts in the future.The major conclusions are as follows:（1） In the period of the Asian monsoon onset,the date of ISM onset is two weeks earlier than the beginning of the Meiyu over the Yangtze River Basin,and a teleconnection mode is set up from the southwestern India via the Bay of Bengal（BOB） to the Yangtze River Basin and southern Japan,i.e.the "southern" teleconnection of the Asian summer monsoon. In the two weeks,Asian monsoon circulation has experienced a series of important changes: ISM setting up,the South Asia High（SAH） moving northward,the onset vortex occurring, the stronger tropical westerly belt extending eastward,and the western Pacific subtropical high（WPSH） jumping northeastward,etc.Consequently,the upper westerly jet stream and the low level jet have been coupled over the East Asia,while Yangtze River Valley happens to lie at the ascending motion area between the upper and low level jet,i.e.right of the entrance of the upper jet stream and left of the low level jet.Such a structure of the vertical circulation can trigger the Meiyu onset in Yangtze River Valley.（2） In the Asian monsoon culmination period,the precipitation of the Yangtze River Basin is influenced significantly by the WNPSM through their teleconnection relationship, and is negatively related to the WNPSM rainfall.It is found from the climatological intraseasonal scale that in the period of the weak WNPSM,the Yangtze River rainfall is influenced simultaneously by the westerly climatological intraseasonal oscillation（CISO） from the tropical west Pacific and the easterly CISO from the tropical Indian Ocean altogether,giving rise to more rainfall than normal there.（3） In contrast to the rainfall over the Yangtze River Basin,the precipitation of northern China(from the 4^th pentad of July to the 3^rd pentad of August) is positively related to the WNPSM.The water vapor transport which is brought by the abnormally strong southeastern monsoon has important impact on the precipitation anomaly in northern China.Through the intraseasonal scale analysis,the reason that more rainfall than normal in northern China may be the mutual influences of northerly CISO from the tropical western Pacific and the southerly CISO from the high latitude region.（4） The summer rainfall in northern China has also a positive correlation with the ISM. During the peak period of ISM,another teleconnection pattern is formed from Northwest India via the Tibetan Plateau to northern China,i.e.the "northern" teleconnection of the Asian summer monsoon.The Indian low usually dominantly impacts on the intensity of the ISM. When the Indian low deepens,the low troughs in mid-high latitudes are also frequently strengthened,and the ridge of the WPSH extends westwards,which is favorable for more rainfall there than normal. （5） The subsystems of the Asia-Pacific summer monsoon have a concurrent variation at the interannual scale,with the oscillation cycle of 2 to 3 years.In other words,when one of the subsystems of the Asian summer monsoon is stronger than normal and the other monsoon subsystems will also be stronger than normal in the same year,and vice versa.The consistent interannual variation of the summer monsoon that is performed by the water vapor transport is more remarkable than by the 850hpa wind.The tropospheric biennial oscillation（TBO） may be an inherent cycle in the Asian-Pacific summer monsoon system,which is closely associated with the atmosphere-ocean interactions over the warm ocean surfaces.更多还原