气象学报  2013, Vol. 71 Issue (3): 476-491   PDF    
http://dx.doi.org/10.11676/qxxb2013.038
中国气象学会主办。
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文章信息

吴捷, 许小峰, 金飞飞, 郭品文. 2013.
WUJie, XU Xiaofeng, JIN Feifei, GUO Pinwen. 2013.
东亚-太平洋型季节内演变和维持机理研究
Researeh of the intraseasonal evolution of the East Asia Pacific pattern and the maintenance mechanism
气象学报, 71(3): 476-491
Acta Meteorologica Sinica, 71(3): 476-491.
http://dx.doi.org/10.11676/qxxb2013.038

文章历史

收稿日期:2012-10-24
改回日期:2013-04-24
东亚-太平洋型季节内演变和维持机理研究
吴捷1, 许小峰2 , 金飞飞3, 郭品文1    
1. 南京信息工程大学大气科学学院, 南京, 210044;
2. 中国气象局, 北京, 100081;
3. 夏威夷大学气象系, Honolulu, HI, 96822
摘要:利用850hPa的纬向风异常建立一个逐候东亚-太平洋(East Asian Pacific,EAP)型指数,研究其季节内演变特征,发现东亚-太平洋型经向波列是东亚夏季风季节内变化的主要模态.其演变过程为:扰动首先出现在北太平洋中部,并通过正压不稳定过程从基本气流中获得能量而发展,在高层罗斯贝波能量向南频散,激发热带对流异常和赤道罗斯贝波,并相互锁相,因赤道罗斯贝波受β效应影响而共同向西移动.热带对流和环流异常在菲律宾附近达到最强,此时在东亚沿岸出现经向三极型波列,此后中低纬度异常继续向西北方向移动,使降水异常在长江流域能维持较长时间.东亚-太平洋型在东亚发展和维持有以下原因:首先,菲律宾暖水上空的对流和低层环流之间存在正反馈;其次,由于海陆热力差异导致暖大陆和冷海洋之间存在特殊的纬向温度梯度和北风垂直切变,东亚-太平洋型在经向上有向北倾斜的斜压结构,能通过斜压能量转换从平均有效位能中获得能量,同时,也能从经向温度梯度的平均有效位能中获得能量.
关键词东亚太平洋型     季节内变化     纬向温差的斜压能源     正压能量转换    
Researeh of the intraseasonal evolution of the East Asia Pacific pattern and the maintenance mechanism
WUJie1, XU Xiaofeng2 , JIN Feifei3, GUO Pinwen1    
1. Institute of Atmospheric Science, Nanjing University of In formation Science and Technology, Nanjing 210044, China;
2. China Meteorological Administration, Beijing 100081, China;
3. Department of Meteorology, University of Hawaii at Manoa, Honolulu, HI 96822, USA
Abstract:A pentad East Asia Pacific(EAP) pattern index based on 850 hPa tonal wind anomalies is established to analyze the intrascasonal EAP variability.It is shown that the EAP-like meridional wave train is the dominant mode of the East Asian Summer Monsoon(EASM) intrascasonal variability.The evolution process is as follows; disturbances firstly occur in the middle of the North Pacific, barotropic energy conversion from the middle latitude mean flow facilitates the development of the middle latitudc center of the anomaly circulation,and the southward dispersion of the Rossby wave energy excites convection anomaly and equatorial Rossby waves which tend to reinforce each other over the tropical western Pacific region to form the main EAP pattern.The low and mid-latitude anomalies then locked together and both move westward because of the equatorial Rossby-wave beta-effect control on its tropical center.The anomalous convection and circulation become strongest near Philippines when a tripolar wave train appears in the East Asian coast, and then the low and mid-latitude anomalies continue moving northwest-ward and weakened though in the Yangtze valley basin precipitation anomaly is able to maintain.The reasons why the EAP pattern develops and maintains in East Asian are as follows:first of all,there exists the positive feedback between convection over the Philippines sea warm pool and the low-level circulation;secondly, the EAP pattern tilts to the north in the meridional direction,resulting from a significant energy supply from baroclinic energy conversion from mean available potential energy associated with land-ocean tonal temperature contrast and thus the meridional wind shear between high and low levels.It also draws energy from mean available potential energy owing to the meridional temperature gradient.
Key words: East Asian Pacific tclcconncction pattern     Intrascasonal variability     Baroclinic energy source from tonal thermal contrast     Barotropic energy conversion    
1 引 言

大气遥相关通常指地球上相隔遥远的地区大气环流异常的显著相关。Wallace等(1981)首先使用单点相关技术,客观地确定了冬季的5种显著遥相关型。Ding等(2005)指出,在北半球夏季存在沿西风急流波导的纬向全球遥相关(CGT)。但在西北太平洋(WNP)和东亚(EA)季风区,气候异常主要受到经向遥相关的控制(Wang et al,2001Lu,2004)。Nitta(19871989)通过研究菲律宾和日本附近云量反映的对流状况,指出二者存在相反的振荡,并称之为太平洋-日本(PJ)型。与此同时,Huang等(19872003)指出,东亚夏季风异常不但受到印度季风的影响,更多与西太平洋副热带高压(副高)的季节内和年际变化有关。当西太平洋暖池位于暖位相时,暖水堆积,菲律宾附近对流异常加强,副高偏北,长江流域和日本中南部地区偏旱,在位势高度场上表现为菲律宾、日本中部和鄂霍次克海附近的“-+-”波列(黄荣辉,1990黄荣辉等,1992),并称为东亚-太平洋(EAP)遥相关型。之后的研究进一步证明,东亚-太平洋型将东亚夏季风系统中西北太平洋季风槽、副高、梅雨槽和鄂霍次克海高压的变化紧密地联系起来,长江中下游的降水异常与东亚-太平洋型密切相关(林建等,1999Hsu et al,2007丁一汇等,2008),东亚-太平洋型还能对台风在中国的登陆地点(黄荣辉等,2010)、华南前汛期6月降水异常(陈锐丹等,2012)产生影响。

在早期的研究中,Huang等(1987)Nitta(1987)均认为,菲律宾附近的异常对流加热,能够激发准定常行星波在球面上沿大圆路径传播(Hoskins et al,1981)时产生该遥相关型。但在夏季,菲律宾附近的对流热源并不在西风带中。Wang等(2005)提出,能量可以通过南风通道向北频散,但在东亚地区低层是西南气流,高层则与低层风向相反,以北风为主。最近Kosaka等(200620082010)提出,该遥相关可看作为一种动力模,能够从基流中获得能量,有自增长机制。也有学者指出,沿亚洲急流频散的中高纬度罗斯贝波对东亚-太平洋型的形成有重要作用(Enomoto et al,2003布和朝鲁等,2008施宁等,20082009)。Lu等(2009)指出,东亚副热带地区的降水异常,可以反过来维持东亚-太平洋这种经向遥相关型。宗海峰等(2008)指出,前期热带太平洋海温异常能对夏季东亚-太平洋遥相