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印度洋海温异常对亚洲主要降水区的影响研究
【作者】 杨明珠；
【导师】 丁一汇；
【作者基本信息】 南京信息工程大学 ， 气象学， 2006， 博士
【摘要】 本文主要通过诊断分析方法研究了印度洋海表温度(SST)的变化及其与亚洲夏季主要降水区降水的关系,并对其机理进行了分析,包括:热带外的南印度洋偶极子(SIOD)SST分布型对印度夏季季风降水(ISMR)和中国降水,以及对大气环流的影响;印度洋SST主模态(LMIO)的变化特征及其对亚洲夏季主要降水区降水和夏季季风环流的影响;LMIO与太平洋SST的关系以及与全球温度变化的关系。主要揭示下列事实:(1)印度洋SST自1950年代以后具有长期增暖趋势,有三次明显跃迁,分别出现在1976年,1986年,1996年,其中70年代中后期的变化是十分明显的,在三次明显增温后,印度洋都分别处于一段相对高的SST水平上;(2)在印度洋明显增温后, ISMR与春季南印度洋SST相关分布型始终是相对稳定的。将春季西南印度洋出现负(正)SSTa,东南印度洋出现正(负)SSTa时定义为正(负)SIOD--PSIOD(NSIOD)。热带外SIOD与热带的印度洋偶极子(IOD)是不同的,其变率比IOD大,并主要出现在春季(IOD主要出现在秋季);(3) SIOD对ISMR的影响是显著的,当PSIOD出现时ISMR往往偏多,NSIOD出现时往往偏少;SIOD与中国降水也有很好的关系。另外,SIOD与季风环流不同系统也有显著相关关系。因而在研究印度洋SST的影响时,要整体考虑印度洋,不仅要考虑热带地区的影响,也要考虑热带外地区的影响;(4)揭示了LMIO特征及其与亚洲夏季降水和环流的关系。LMIO具有显著的整个海盆一致的升温趋势,它可能是印度夏季风减弱的一个主要因子,也是造成中国主要降水区南移的一个因子;(5) LMIO和热带太平洋SST通常具有同位相的变化,因而印度洋是全球大洋协同变化的主要部分之一,这种协同变化的作用在考虑海气相互作用时要加以重视。而LMIO与暖池之间显示出更加密切的联系,两者对全球温度变化都具有显著贡献。
【Abstract】 The relationship between Indian Ocean sea surface temperature (SST) and Asiansummer rainfalls is investigated using diagnostic methods and the impactingmechanism is also studied, which include the study of the impact of extratropicalSouth Indian Ocean Dipole (SIOD) on Indian summer monsoon rainfalls (ISMR),Chinese rainfalls and general circulation;investigation of the leading mode of IndianOcean (LMIO) characterized by warming trend of all the basin and its relationshipwith Asian summer rainfalls and summer monsoon circulation and research ofrelationship between LMIO and Pacific SST. Major conclusions are as follows:(1) The warming trend of Indian Ocean SST is significant after 1950s, andthere is abrupt warming in 1976, 1986 and 1996 respectively. Afterevery times of the abrupt warming, Indian Ocean SST remains at ahigher level.(2) The relationship between ISMR and extratropical south Indian OceanSST is rather stable even after the several abrupt warming events,although is changed a lot in other ocean areas, especially in middle andwest tropical Pacific. The SST pattern, when southwest Indian Ocean isnegative (positive) and southeast Indian Ocean positive (negative), isdefined as positive (negative) south Indian Ocean (SIOD). Comparingwith IOD brought forward by Saji, SIOD happens mainly in spring andits variability is more significant than IOD.(3) The relationship between SIOD and ISMR is remarkable. ISMRincreases (decreases) in most of PSIOD (NSIOD) years. The impacts ofSIOD on Chinese rainfalls and subsysterms of Asian summer monsoonare significant too. As a holistic system, both the tropical region andextratropical region have to be taken into account when study theinfluence of Indian Ocean SST.(4) The character of LMIO and relationships between LMIO and Asiansummer rainfalls and circulation are revealed. LMIO characterized bywarming trend of the whole Indian Ocean SST is probable one of themajor factors to weaken Indian summer monsoon and make the rainbellof China shift southward.(5) The trend of LMIO and tropical Pacific SST are usually in phase duringthe climate change process. In the co-variability of global oceans, IndianOcean is very important and should take into account in considering theglobal air-sea interaction. LMIO and Pacific Warmpool have muchcloser relationship, and both significantly contribute to the variation ofglobal surface temperature.