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A Cautionary Note on the Long-term Trend in Activity of the Madden-Julian Oscillation During the Past Decades
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2019
Source: Geophysical Research Letters, 46, 14063– 14071.
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Journal Title:Geophysical Research Letters
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NOAA Program & Office:
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Description:Recent studies suggest that frequency of active phases of the Madden-Julian Oscillation (MJO) over the Maritime Continent and western Pacific, that is, the MJO Phases 4-6 defined by the real-time multivariate MJO (RMM) index, has increased in recent winters. A robust positive trend in MJO Phase 4-6 days during 1979-2015 winters is confirmed in this study. Our analyses, however, suggest that this trend could be exaggerated due to the blended low-frequency variability signals in the RMM. When the winter RMM is reconstructed using anomalous fields after removing their winter mean instead of the previous 120-day mean as for the original RMM, the robust trend in MJO Phase 4-6 days can no longer be detected. Therefore, cautions need to be exercised when applying the RMM for studies on the low-frequency variability and climate trend in MJO activity and using the derived MJO variability to interpret associated changes in climate systems.
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Source:Geophysical Research Letters, 46, 14063– 14071.
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Rights Information:CC BY-NC-ND
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Compliance:Submitted
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