Indian Ocean Dipole-related Predictability Barriers Induced by Initial Errors in the Tropical Indian Ocean in a CGCM
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Using GFDL CM2p1 (Geophysical Fluid Dynamics Laboratory Climate Model, version 2p1), the effects of initial sea temperature errors on the predictability of the Indian Ocean Dipole (IOD) are explored. When initial temperature errors are superimposed on the tropical Indian Ocean, a winter predictability barrier (WPB) and a summer predictability barrier (SPB) exist in IOD predictions. The existence of the WPB has a close relation with El Niño-Southern Oscillation (ENSO) in the winter of the growing phase of positive IOD events. That is, when ENSO exists in winter, no WPB appears in IOD predictions, and vice versa. In contrast, there is no inherent connection between the existence of the SPB and ENSO. Only the dominant spatial pattern of SPB-related initial errors is studied in this paper, which presents a significant west-east dipole pattern in the tropical Indian Ocean and is similar to that of WPB-related initial errors in previous studies. The SPB-related initial errors superimposed on the tropical Indian Ocean induce the sea surface temperature (SST) and wind anomalies in the tropical Pacific Ocean. Then, under the interaction between the Indian and Pacific oceans through the atmospheric bridge and Indonesian Throughflow, a west-east dipole pattern of SST errors appears in summer, which is further strengthened under the Bjerknes feedback and yields a significant SPB.
Key wordspredictability barrier initial errors Indian Ocean Dipole Indian Ocean
利用GFDL CM2p1模式, 本文探讨了初始海温误差对印度洋偶极子(IOD)事件可预报性的影响. 当热带印度洋存在初始海温误差时, IOD预报发生了冬季预报障碍(WPB)现象和夏季预报障碍(SPB)现象. WPB发生与否与正IOD事件发展位相冬季的厄尔尼诺-南方涛动(ENSO)有关. 即当冬季存在ENSO时, IOD预测不发生WPB现象, 反之亦然. 相比之下, SPB发生与否和ENSO没有必然联系. 此外, 进一步探讨了最容易导致SPB现象的初始海温误差的主要模态, 指出该模态在热带印度洋上表现为东-西偶极子型, 这和前人研究中最容易导致WPB现象的初始海温误差模态相似. 当在热带印度洋上叠加这些初始海温误差后, 热带太平洋上出现了海表温度异常和风场异常, 进而通过大气桥和印尼贯穿流的作用影响热带印度洋, 使之在夏季出现了东-西偶极子型的海表温度异常, 该异常在Bjerknes作用下快速发展, 加强, 最终导致SPB现象的发生.
关键词预报障碍 初始误差 印度洋偶极子 印度洋
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This work was jointly sponsored by the National Key Research and Development Program of China (Grant No. 2017YFA0604201), the Strategic Priority Research Program of Chinese Academy of Sciences (Grant No. XDA20060501), the National Natural Science Foundation of China (Grant Nos. 41876024 and 41530961), and the National Programme on Global Change and Air-Sea Interaction (Grant No. GASI-IPOVAI-06).
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