摘要
用近51年（1951-2001年）观测资料，研究太平洋年代际振荡（PDO）冷暖位相中国降水量准2年主振荡型传播特征的差异，并讨论对应的全球500hPa环流低频波列传播途径的变化及可能原因。同时提出年际振荡强度不稳定指数，讨论了中国降水和全球500hPa高度准2年周期振荡（QBO）强度时间不稳定的空间分布。通过主振荡型分析（POP）发现，在PDO冷位相（1951～1976年），准2年时间尺度的中国降水POP1的主要活动区域在长江中游地区，对应的500hPa低频场是大西洋欧亚波列（AEU）和西大西洋遥相关型（WA）以及南太平洋副热带波列（SSP）；在PDO暖位相（1977-2001年），POP1的活动区域迅速北移并扩大到整个长江和淮河流域，对应的500hPa低频场变为欧亚太平洋-南印度洋-南北大西洋波列（EUP—SI—SNA）。因此，PDO冷暖位相中影响中国降水准2年主振荡模态的低频波列的传播途径和强度存在显著差异，PDO对中国降水量准2年主振荡型主要模态（POP1）及其伴随的全球500hPa环流低频波列活动区域的时间变化有重要调制作用，与两个半球中纬度西风气流强度的年代际变化密切相关。由振荡强度时间变化指数分析表明，中国降水QBO强度不稳定区域位于长江中游、长江下游、浙江东部、广东东部、华北地区和青藏高原东北侧附近地区，这些地区降水QBO的强度随PDO位相转变而发生显著的年代际突变。对于全球500hPa高度，其QBO强度不稳定区域在南太平洋中高纬度、副热带南北大西洋地区和亚洲、北太平洋、北美大陆中高纬度地区、北半球副热带西太平洋地区以及南北半球热带和副热带东太平洋地区，表现为对于赤道的非对称空间分布，特别是南北太平洋热带和副热带地区500hPa环流QBO强度在年代际时间尺度上呈现正负反向变化的空间结构，而且南北极附近地区的QBO强度在PDO暖位相显著增强，反映了全球大气环流QBO强度与PDO相互作用的空间特征。
Based on the observed data during the period of 1951 - 2001, the different characteristics of the propagation of the principal biennial oscillation pattern of the rain in China are analyzed for the cool （1951 - 1976） and warm （1977 - 2001） phase of the Pacific Decadal Oscillation （PDO）, and the difference and cause of the propagation of the low frequency wavetrains at 500 hPa associated with the biennial oscillation of the rain in China are also investigated. An interannual oscillation instability index is introducted, and the spatial distributions of the nonstationary intensity for quasi-biennial oscillation （QBO） of the China rain and global 500 hPa height are discussed. The principal modes of the biennial oscillation for China rain are identified by means of the Principal Oscillation Pattern analysis （POP） for the different phase of PDO. It is found that the main active region of the biennial oscillation is in the middle reaches of the Yangtze River, which is connected with wavetrain of 500 hPa from East Asia through Eurasian continent into Northern Atlantic （AEU） and Western Atlantic teleconnection pattern （WA） and subtropical southern Pacific wavetrain （SSP）, for the PDO cool phase. While the active region shifts northward and extends toward the whole region of the Yangtze River and the Huaihe River valleys, which is linked to Eurasian Pacific wavetrain and southern Indian Ocean and South- North Atlantic wavetrain （EUP- SI- SNA）, for the PEO warm phase. Hence, there are significant differences for the propagation paths and intensity of low frequency waves associated with principal biennial oscillation modes of China rain between cool and warm phase of PDO, and the paths of propagation for the principal mode of China rain （POP1） and the active regions associated with low frequency wave are regulated significantly by PDO. It is closely related to the interdecadal variations of the intensity for westerly wind in middle latitude of the Northern and Southern hemispheres. By analyzing the interannual oscillation instability index, it is found that the instable regions are in the middle and lower reaches of the Yangtze River, the eastern regions of Zhejiang and Guangdong provinces, the northern part of China and near the northeast side of Tibetan Plateau for QBO intensity of China rain, implying that an interdecadal abrupt change of QBO intensity related to the phase transition of PDO is significant. For the global 500 hPa height, nonstationary biennial oscillations are identified in the mid- and high-latitude regions of the southern Pacific, subtropical regions of the southern and northern Atlantic, the mid- and highlatitude regions of Asian and northern American continent and northern Pacific, subtropical western Pacific in the Northern Hemisphere and the tropical and subtropical eastern Pacific in the Southern and Northern hemispheres, which exhibits an asymmetry structure to the equator. In particular, there is a seesawlike fluctuation in the southern tropical and northern subtropical Pacific for the intensity of QBO in decadal timescales, while there is the enhancing in Arctic and Antarctic for the PDO warm phase, which reflects the spatial features of interaction between the intensity of QBO for the global general circulations and PDO.
出处
《大气科学》
CSCD
北大核心
2006年第1期131-145,共15页
Chinese Journal of Atmospheric Sciences
