【作者】 刘凯；

【导师】 冯俊乔； 段华；

【作者基本信息】 山东科技大学 ， 数学， 2023， 硕士

【摘要】 南印度洋副热带海表面温度(Sea Surface Temperature,SST)的变化能影响海流、中纬度风暴路径、热带和温带之间的遥相关以及经向大气环流等,在南部非洲的年代际气候变化中起着重要作用。南印度洋副热带偶极子(Subtropical Indian Ocean Dipole,SIOD)是南印度洋重要的年际气候变化,为了对SIOD有着更深入的认知,本文利用Hadley中心的海表面温度数据、美国国家环境预报中心的大气再分析数据集Ⅰ(NCEP-NCAR Reanalysis1,NCEP)和欧洲中期天气预报中心的海洋再分析数据(Ocean Reanalysis System4,ORAS4)等,分析了1958～2020年SIOD年代际转变的特征和物理机制。结果显示,2000年之前,SIOD存在2～4 a和4～6 a两个年际主周期,但近二十年(2000～2020年)其年际周期缩短为1.5～2.0 a,并且SIOD的小波谱密度也在逐渐减小。除此之外,在1987年和2004年,SIOD经历了两次显著的年代际转变,在振幅和空间模态方面均有体现。1958～1986年(P1)期间强度最大,1987～2003年(P2)期间最弱,2004～2020年(P3)期间居中;P1期间SIOD的最大正SST异常(SSTA)中心位于(46°E～80°E,44°S～28°S),P2期间向西南移动到(35°E～65°E,48°S～34°S),同时负SSTA中心较P1期间向南北方向延伸,P3期间正、负SSTA中心又回到P1时期的位置。进一步研究发现,SIOD与南极涛动(Antarctic oscillation,AAO)和厄尔尼诺-南方涛动(El Ni(?)o-Southern Oscillation,ENSO)在统计上存在显著的相关关系,SIOD的年代际转变受AAO和ENSO的影响。在P1时期,SIOD与AAO之间显著同期正相关,在此之后相关性减弱;SIOD与ENSO的关系在1958～1984年和1996～2020年呈现显著负相关,在1985～1995年期间关系不显著;MH与SIOD的关系在P3时段之前与AAO类似,但在P3时期二者有着显著的正相关。通过合成分析与海洋混合层热收支分析发现,AAO与ENSO主要通过调制马斯克林高压(MH)而影响海表面热通量(特别是潜热通量)的变化,进而影响SIOD。本文最后分析了SIOD与ENSO的关系,结果发现,二者之间存在显著的超前滞后关系,并且这种关系也存在年代际转变,主要与太平洋年代际振荡(Interdecadal Pacific Oscillation,IPO)的相位转变有关。更多还原

【Abstract】 The variation of sea surface temperature(SST)in the subtropical southern Indian Ocean plays an important role in the decadal climate change in southern Africa,which can affect ocean currents,mid-latitude storm tracks,tropical and temperate teleconnections,and meridional atmospheric circulation.The subtropical Indian Ocean dipole(SIOD)is an important interannual climate variability in the Southern Indian Ocean.Using monthly mean observed SST data from the Hadley Centre,atmospheric reanalysis data from National Centers for Environmental(NCEP)and ocean reanalysis data from the European Centre for Medium Range Weather Forecasts(ORAS4),interdecadal characteristics and mechanism of the SIOD were investigated from 1958 to 2020.The results show that before 2000,SIOD is characterized by a mix of 2-4 years and 4-6 years of interannual timescale,but the period gradually shifts to a shorter period of about 1.5-2 years in the last 20 years,and the wavelet spectral density of SIOD is also gradually decreasing.The spatial and intensity of SIOD exhibited two significant interdecadal shifts around 1987 and 2004 in addition to the above-mentioned interannual variability.Compared to 1987～2003(P2),there was greater amplitude in 1958～1986(P1)and2004～2020(P3).The center of the positive SSTA shifted from(46°E～80°E,44°S～28°S)to(35°E～65°E,48°S～34°S)and the negative center extended north and south relative to those in P1.Finally,the center returned back to the P1 position during P3.Further studies show that the decadal transition of SIOD is influenced by the Antarctic Oscillation(AAO)and the El Ni(?)o-Southern Oscillation(ENSO),there is a statistically significant correlation between SIOD and AAO and ENSO.Prior to the mid-1980s,SIOD had a significant correlation with AAO.The relationship between ENSO and SIOD was significantly negative except for 1985-1995.In addition,the composite analysis and mixed heat budget demonstrated that AAO and ENSO influence changes in heat flux(especially latent heat flux)on the sea surface primarily by modulating Mascarene high(MH),thereby impacting SIOD.At the end of the paper,the relationship between SIOD and ENSO was analyzed,and the results show that there is a significant relationship between SIOD and ENSO,and this relationship also exists with decadal transition,mainly related to the phase transition of the Interdecadal Pacific Oscillation(IPO).更多还原