【摘要】 利用1979—2012年逐月Hadley中心海表温度、欧洲中期天气预报中心次表层海温、NCEP/NCAR风场再分析资料,对两类中太平洋(CP)El Nio及耦合的大气环流特征进行分析。结果表明,第一类CP El Nio(CP-ⅠEl Nio)增暖中心位于Nio4区且关于赤道对称;第二类CP El Nio(CP-ⅡEl Nio)的Nio4区与热带东北太平洋区域(NEP,130~110°W、15~25°N)同位相变化,冬季成熟后形成关于赤道非对称的带状增暖结构。进一步的研究表明,两类CP El Nio次表层结构存在差异:CP-ⅠEl Nio冬季次表层海温异常(SOTA)在中东太平洋与西太平洋呈显著偶极分布;CP-ⅡEl Nio在中、西太平洋位相相反但东太平洋异常较弱,且经向异常主要在赤道及其以北。两类CP El Nio耦合的大气环流特征不同:CP-ⅠEl Nio冬季异常Walker环流上升中心位于赤道上空,经向风向赤道辐合,低纬地区Hadley环流加强;CP-ⅡEl Nio冬季低层向北越赤道气流加强,Walker环流上升中心移到赤道以北,低纬地区Hadley环流减弱。更多还原

【Abstract】 The new El Nio phenomenons named central Pacific( CP) El Nio are discussed all over the w orld in the most nearly three decades. Specially,tw o types of CP El Nio w hich have different sea surface temperature anomalies( SSTA) structures are investigated in recent years. In order to recognize the different sea-air interaction processes of tw o types of CP El Nio comprehensively,in this research,w e base on monthly Hadley Center sea surface temperature( Had ISST),European Centre for M edium-Range Weather Forecasts( ECM WF) ocean subsurface temperature and NCEP/ NCAR reanalysis datasets for 1979—2012,the characteristics of tw o types of central Pacific( CP) El Nio and coupled atmospheric processes are studied. The results show that there are tw o types of CP El Nio,the difference lies in sea surface temperature anomalies distribution in the tropical pacific. A type of CP El Nio( CP-Ⅰ El Nio) events have symmetrical structure about the equator in the w inter,the w arming center locate at Nio4 regions and stretch eastw ard into eastern pacific. Another type of CP El Nio( CP-Ⅱ El Nio),the sea surface temperature anomalies change in phase betw een Nio4 regions and tropical northeast pacifc areas( NEP,15- 25° N,130- 110° W),a banded and asymmetric structure of SSTA forms in the w inter and show s horseshoe-shaped cold SSTA distribution in the w estern pacific. Further research indicates that the subsurface temperature anomalies( SOTA) of tw o types of El Nio are different. In the CP-Ⅰ El Nio w inter,a zonal dipole mode forms betw een w estern and central-eastern pacific,the subsurface temperature of central-eastern pacific raise significantly,the meridional structure are also symmetric,a major positive SOTA center locates at the equator. How ever,in the CP-Ⅱ El Nio w inter,a zonal dipole mode confines in the w estern and central pacific,the w arming develop at the upper subsurface in the central pacific,the SOTA in the eastern pacific are tiny. M eridional SOTA also confine in the north hemisphere,tw o major positive anomalies center locate at the the equator and near 10°N. Characteristics of atmospheric circulation have distinct difference among CP-Ⅰ El Nio and CP-Ⅱ El Nio. In the CP-Ⅰ El Nio w inter,the abnormal upw elling branch of w alker circulation are over equator near the longitude of 180°,the abnormal dow nw elling branch locate at equatorial w estern and eastern pacific w hich responded to symmetric SSTA. In the low level atmosphere,there are significant w esterly w ind anomalies and convergent meridional w ind anomalies in the equatorial area. The Hadley circulation intensify in the low latitude regions. How ever the mass transport betw een 20°N and 30°N are reduced w hich lead to southw ard move of dow nw elling branch of the Hadley circulation. In the CP-Ⅱ El Nio w inter,the cross-equatorial southw est flow strengthen in the low level atmosphere,the upw elling center of Walker circulation move to north hemisphere w hich responded to asymmetric SSTA,the Hadley circulation w eak in the low latitude regions to the contrary. In addition,the sea surface heat flux are investigated preliminary. In the August to December,the positive sea surface heat flux anomalies are observed in the CP-Ⅱ El Nio,w hich contribute to the w arming in the central pacific and tropical northeast pacific. It show s that the w ind-evaporation-SST processes exist in the tropical ocean. contrarily,in the CP-Ⅱ El Nio,negative sea surface heat flux anomalies damp the developments of SSTA.更多还原