IOCAS-IR  > 海洋环流与波动重点实验室
IOD-ENSO前兆遥相关的年代际变化及动力机制
徐鹏
学位类型博士
导师袁东亮
2016-05
学位授予单位中国科学院大学
学位授予地点北京
学位专业物理海洋学
关键词印度洋偶极子(iod) 厄尔尼诺与南方涛动(enso) 印度尼西亚贯穿流(itf) 印太暖池 Enso可预报性
摘要本文利用观测资料、CCSM4(Community Climate System Model version 4)模拟数据和CESM1(Community Earth System Model version 1)数值实验,对热带东南印度洋秋季海洋异常与随后四个季节热带印太海洋异常进行滞后相关分析,研究了印度洋偶极子(IOD)与ENSO一年滞后相关(简称为IOD-ENSO前兆遥相关)的年代际变化,并探讨了海洋通道机制在IOD-ENSO前兆遥相关中的重要作用,初步分析了印太暖池区海表面温度(SST)变率通过调制沃克环流对IOD-ENSO前兆遥相关的影响。
在长期观测资料中,热带东南印度洋秋季(北半球,以下同)SST异常与Niño3.4指数一年滞后相关经7-11年滑动窗口平滑后,呈现出正、负位相交替的年代际变化。国际耦合模式比较计划(CMIP5)的CCSM4长期历史模拟数据中也存在与观测分析类似的IOD-ENSO前兆遥相关的年代际变化。模拟数据中,以上年代际变化正位相阶段,IOD-ENSO的合成滞后一年相关分析表明,IOD引起的印尼贯穿流(ITF)年际异常造成赤道西太平洋次表层海温异常,随后该海温异常东传并上浮,影响冷舌海域SST和ENSO发生与发展,这被称为IOD-ENSO前兆遥相关的“海洋通道”机制,并且模拟与观测结果大体一致。相比之下,该海洋通道机制在IOD-ENSO前兆遥相关负位相阶段同样在赤道西太平洋引起了次表层海温异常,但因赤道中、东太平洋温跃层较正位相阶段更深,该海温异常没能与冷舌区SST异常形成显著的相关。模拟数据中的ITF输运年际变化相比观测结果较弱,表明海洋通道机制在CCSM4模式中被低估,但是模式高估了赤道西、中太平洋上空的大气桥,后者在赤道太平洋引起了与IOD相关的不真实海洋异常,表明模式大气桥模拟缺陷。
在CESM1数值模式的控制实验中,海洋与大气在热带印太海域耦合;在敏感实验中,印太暖池SST替换为气候态年平均,两个实验结果的比较显示,印太暖池对大气强迫的改变并没有影响年代际变化正位相期间海洋通道机制在IOD-ENSO前兆遥相关中的主导地位,但是会导致春夏两季赤道中、东太平洋上空沃克环流圈的增强,后者进而造成赤道东太平洋温跃层变浅并增强了IOD-ENSO前兆遥相关的正位相阶段。
其他摘要In this study, the observational datasets, CCSM4 (Community Climate System Model version 4) simulations and CESM1 (Community Earth System Model version 1) numerical experiments, are used in the lag correlation analyses between the oceanic anomalies in the southeastern tropical Indian Ocean (STIO) in fall and the Indo-Pacific oceanic anomalies in the following four seasons, to investigate the decadal variability of 1-year time lag correlation  between Indian Ocean Dipole (IOD) and El Niño-Southern Oscillation (ENSO) and the role of the oceanic channel dynamics in the relation (the IOD-ENSO precursive teleconnection), and to examine the effect of the SST (sea surface temperature) variabilities in the Indo-Pacific Warm Pool (IPWP) on the IOD-ENSO precursive teleconnection by modifying the Walker circulation.
The lag correlations between the observed SST anomalies (SSTA) in STIO in fall and those in the Pacific cold tongue at the one-year time lag are shown to have decadal variability after filtering with running windows of 7-11 years. Similar decadal variability has also been identified in the historical simulations of CCSM4 that participates in the Coupled Model Intercomparison Project phase-5 (CMIP5). The dynamics of the inter-basin teleconnection during the positive phases of the decadal variability are diagnosed in the simulations using composite lag correlations, which suggest that the interannual variations of the Indonesian Throughflow (ITF) associated with IOD produces subsurface temperature anomalies in the western equatorial Pacific Ocean to propagate to the east. This connection is called the “oceanic channel” dynamics of the IOD-ENSO precursory relation and is shown to be consistent with the observational analyses. In comparison, the subsurface lag correlations in the western Pacific Ocean during the negative phases of the decadal variability are still dominated by the oceanic channel dynamics, but do not correlate well with the SSTA in the cold tongue due to a deeper thermocline in the eastern equatorial Pacific. The CCSM4 model is found to underestimate the interannual variability of the ITF transport but overestimate the westerly wind anomalies in the western-central equatorial Pacific, which force unrealistic anomalies in the equatorial Pacific Ocean associated with the IOD, indicating model deficiency in simulating  the “atmospheric bridge”.
Lag correlation analyses are compared between the CESM1 control experiment, in which the atmosphere and the ocean over the Indo-Pacific Oceans are fully coupled, and the sensitivity experiment, in which the time-varying SST over the IPWP are replaced with annual mean climatological SST when forcing the atmosphere. The comparison of the control and the sensitivity experiments suggests that the removal of IPWP SST variability has little effects on the dominance of the oceanic channel dynamics during the positive phases of the decadal variability of the IOD-ENSO precursive relation. However, the seasonal variations of the tropical Indo-Pacific atmospheric bridge are greatly altered by the modification of the IPWP SST variability. In the sensitivity experiment, the Walker circulation is greatly enhanced in summer and fall so that a shallower thermocline in the central and eastern equatorial Pacific Ocean is established, which strengthens the positive phases of the decadal variability and weakens the negative.
学科领域海洋科学 ; 物理海洋学
语种中文
文献类型学位论文
条目标识符http://ir.qdio.ac.cn/handle/337002/112499
专题海洋环流与波动重点实验室
作者单位中国科学院海洋研究所
推荐引用方式
GB/T 7714
徐鹏. IOD-ENSO前兆遥相关的年代际变化及动力机制[D]. 北京. 中国科学院大学,2016.
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