索马里和澳大利亚越赤道气流的协同变化与我国夏季降水型  

Connection of the interannual seesaw of the Somali-Australian cross-equatorial flows with China summer rainfall

作　　者：李琛[1] 李双林[1] 

机构地区：[1]中国科学院大气物理研究所,中国科学院气候变化研究中心,北京100029

出　　处：《科学通报》2016年第13期1453-1461,共9页Chinese Science Bulletin

基　　金：国家重点基础研究发展计划(2012CB417403;2015CB453202);中国科学院战略性先导科技专项(XDA110104)资助

摘　　要：利用美国国家环境预报中心-国家大气研究中心（NCEP/NCAR）逐月再分析资料,结合我国国家气候中心提供的160站月平均降水资料（1970～2012年）,在以前工作基础上,进一步讨论了索马里与澳大利亚北部低空越赤道气流的协同变化与我国夏季降水异常型的联系.结果表明：该二支越赤道气流的反相关协同变化（seesaw）与我国西南-东北走向的降水异常型密切相关.当索马里越赤道气流偏强（偏弱）而澳大利亚北部越赤道气流较弱（较强）时,我国夏季降水型呈西南-东北走向,即长江上游和中游、黄河流域以及华北大部分地区降水偏多（偏少）.这种联系的产生同西太平洋副热带高压位置变化有关,在各月份的表现不尽相同.对应索马里越赤道气流增强和澳大利亚越赤道气流减弱,7月副高西伸,8月副高位置偏北.由于这种越赤道气流间的反相关关系从5月开始出现,在整个夏季有很好的持续性,所以它对我国夏季西南-东北走向的降水异常型具有预测意义.The low-level Cross-Equatorial Flows（CEFs） over the Indian Ocean and western Pacific regions have been recognized as essential components of the Asian-Australian monsoon systems. The variations of the CEFs play a key role in the year-to-year monsoon rainfall anomalies. Recently, several studies have illustrated that the changes of the two CEFs are not independent with each other. A negative（seesaw） correlation at interannual timescale between the Somali CEF and the Australian CEF during boreal summer（Jun-July-August） has been noticed. In contrast to the Indian summer monsoon（ISM）, for which the Somali CEF plays a dominant role in the moisture transport, both the Somali and Australian CEFs show significant contributions to the East Asian summer monsoon（EASM）. Thus, it may be more useful to consider the effect of the combined CEFs on the EASM. To describe the opposite interannual variability between the Somali and Australian CEFs, our previous study has proposed a CEF-seesaw index which is defined by the difference between the standardized Somali and Australian CEFs. A higher（lower） CEF-seesaw index represents an intensified（weakened） Somali CEF but a weakened（intensified） Australian CEF. The CEF-seesaw index shows a closer correlation with EASM than the individual CEF does. In addition, the seesaw-EASM connection is even closer than the ENSO-EASM connection. Thus, the CEF-seesaw and its close connection to Asian summer monsoon may represent an intrinsic variability within the Asian-Australian monsoon system. This contributes to better understanding of the interannual variability of summer rainfall in the Asian-Australian monsoonal region. In the present study, we further analyze the relation of the CEF-seesaw to the China summer rainfall anomaly patterns during 1970–2012 using the NCEP/NCAR reanalysis data and the China's Mainland 160-station precipitation. Since we focus on the interannual time scale, a linear detrend is first removed. Then the fast Fourier transform（FFT） fil

关 键 词：越赤道气流 反相关 我国夏季降水异常型 西南-东北走向 年际变化 

分 类 号：P426.6[天文地球—大气科学及气象学]