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A correlation of mean period of MJO indices and 11-yr solar variation

Abstract : This paper focuses on the decadal to multi-decadal evolution of the spectral properties of the Madden-Julian Oscillation (MJO). Guided by former studies, we test whether the ∼11-yr (Schwabe) cycle of solar activity could be reflected in the spectral features of MJO indices: namely, we study the evolution of MJO mean period within different period ranges and compare these with the evolution of solar activity. We focus on solar proxies best linked to UV emission and cosmic rays: sunspot number WN, F10.7 flux, core-to-wing ratio MgII, and galactic cosmic rays (GCR). A clear solar signature in MJO spectral properties is indeed found and shown to be both statistically significant and robust. UV proxies are found to be better correlated with MJO mean period than GCR, thus supporting rather the ozone mechanism of solar impact on MJO. The overall correlation with solar activity is found to be stronger in the Indian Ocean. Long periods (e.g. 50-80 day) are better correlated with solar activity than shorter periods (e.g. 30-60 day). A marked change in the relationship between MJO mean period and solar activity takes place in the declining phase of solar cycle 23, adding to its unusual character.
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https://hal-insu.archives-ouvertes.fr/insu-03583348
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Submitted on : Monday, February 21, 2022 - 5:12:34 PM
Last modification on : Wednesday, February 23, 2022 - 3:34:57 AM

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Elena Blanter, Jean-Louis Le Mouël, Mikhail Shnirman, Vincent Courtillot. A correlation of mean period of MJO indices and 11-yr solar variation. Journal of Atmospheric and Solar-Terrestrial Physics, 2012, 80, pp.195-207. ⟨10.1016/j.jastp.2012.01.016⟩. ⟨insu-03583348⟩

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