An Analysis of Nonlinear Relationship between the MJO and ENSO

Tang, Youmin; Yu, Bin

doi:10.2151/jmsj.86.867

Cited by 12 publications

(5 citation statements)

References 44 publications

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“…The Madden‐Julian Oscillation (MJO) is the dominant component of the intraseasonal variability in the tropics and propagates eastward around the global tropics with a cycle on the order of 30–60 days (Madden & Julian, ; Tang & Yu, ). One would expect that the MJO might trigger the formation or enhance the occurrence of the Sumatra Squalls in the study area.…”

Section: Discussionmentioning

confidence: 99%

Stable Isotopes of Precipitation During Tropical Sumatra Squalls in Singapore

Goodkin

Kurita

et al. 2018

JGR Atmospheres

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Sumatra Squalls, organized bands of thunderstorms, are the dominant mesoscale convective systems during the intermonsoon and southwest monsoon seasons in Singapore. To understand how they affect precipitation isotopes, we monitored the δ value of precipitation daily and continuously (every second and integrated over 30 s) during all squalls in 2015. We found that precipitation δ18O values mainly exhibit a “V”‐shape pattern and less commonly a “W”‐shape pattern. Variation in δ18O values during a single event is about 1 to 6‰ with the lowest values mostly observed in the stratiform zone, which agrees with previous observations and modeling simulations. Reevaporation can significantly affect δ values, especially in the last stage of the stratiform zone. Daily precipitation is characterized by periodic negative shifts in δ value, largely associated with the squalls rather than moisture source change. The shifts can be more than 10‰, larger than intraevent variation. Initial δ18O values of events are highly variable, and those with the lowest values also have the lowest initial values. Therefore, past convective activities in the upwind area can significantly affect the δ18O, and convection at the sampling site has limited contribution to isotopic variability. A significant correlation between precipitation δ18O value and regional outgoing longwave radiation and rainfall in the Asian monsoon region and western Pacific suggests that regional organized convection probably drives stable isotopic compositions of precipitation. A drop in the frequency of the squalls in 2015 is related to weak organized convection in the region caused by El Niño.

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Section: Discussionmentioning

confidence: 99%

Stable Isotopes of Precipitation During Tropical Sumatra Squalls in Singapore

Goodkin

Kurita

et al. 2018

JGR Atmospheres

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“…In phases 8–1, it is also dominated by the EOF2 but with an opposite sign. However, the difference between EP and CP La Niña is smaller than in phases 4–5, suggesting the possible asymmetry or nonlinearity of the MJO‐ENSO relationship (e.g., Tang & Yu, 2008). Besides, we found that the EOF2 mode under the EP La Niña matches more with the standard eigenmodes of RMM1 (Wheeler & Hendon, 2004) and OMI2 (Kiladis et al., 2014), thus the projection coefficient against the EOF2 might be weakened mathematically under the CP La Niña.…”

Section: Resultsmentioning

confidence: 99%

Distinct MJOs Under the Two Types of La Niña

Wei

Ren

2022

JGR Atmospheres

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El Niño‐Southern Oscillation (ENSO) strongly influences the interannual variations of Madden‐Julian Oscillation (MJO)—the dominant mode of tropical intraseasonal variability. Previous studies have revealed more about the impacts of the diversified El Niño on MJO, but less about those of the La Niña diversity. Using observations and global climate model experiments, this study demonstrates that MJO undergoes distinct variations and Pacific teleconnections when La Niña varies between eastern‐Pacific (EP) and central‐Pacific (CP) types. Compared to the CP La Niña, MJO under the EP La Niña is more energetic over the southern Maritime Continent–South Pacific Convergence Zone and can propagate faster and further with a broader zonal circulation scale over the Indo‐Pacific warm pool. The stronger and faster MJO under the EP La Niña is associated with more vigorous ascending motions, higher moisture content and stronger moistening in the lower‐level atmosphere ahead of the MJO deep convection. Although the meridional moisture advection exists as the fundamental mechanism of MJO eastward propagation, the distinct MJO under the two types of La Niña primarily results from the different lower‐tropospheric moistening due to the zonal moisture advection. Both the background mean and anomalous zonal winds and moisture gradients are stronger under the EP La Niña, thereby causing a remarkable invigoration effect of zonally advective moistening. Diverse extratropical circulation responses of distinct MJOs are also discussed. These results should improve our understanding of the whole ENSO diversity paradigm that influences MJO and teleconnections.

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“…The original time series are now passed through a band-pass Lanczos filter to retain only the cycles with periods within the relevant timescales. The filtered data-sets then have been subjected to EOF analysis with varimax rotation and the leadings PCs are retained according to the Scree test [31] and the North criteria [32]. After the PCs time series have been extracted, the variations in the ISO magnitude and was studied using statistical methods.…”

Section: Methodsmentioning

confidence: 99%

On the Annual Variations in the Amplitude of 25-70-Day Intraseasonal Atmospheric Oscillations in Central Africa

Sandjon¹

2016

EARTH

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In this paper we analyzed the annual variations in the 25-70-day intraseasonal atmospheric oscillations in central Africa, for the period 1981-2010, using the Outgoing Longwave OLR data. We then extracted the amplitude time series of the dominant modes of intraseasonal variability in 25-70 days filtered OLR anomalies, using Empirical Orthogonal Functions (EOF) analysis. The EOF analysis has shown that three dominant modes characterized the intraseasonal atmospheric oscillation in Central Africa. The amount of variance explained by these three retained EOFs are 19.3%, 13.6% and 11.8% respectively, and they exhibit higher spatial loading over Northern Congo, Southern Ethiopia, and Southwestern Tanzania, respectively. The analysis of Principal Components (PCs) time series showed that the amplitude and of the intraseasonal oscillations (ISO) exhibit large annual variations. In fact the highest values of ISO amplitude are generally observed during October-April season, and much weakened signal the rest of the year. The fraction of yearly Madden Julian Oscillation (MJO) power, occurring within October-April season are 79.3%, 77.92%, 78.73% for EOF1, EOF2, and EOF3, respectively.

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An Analysis of Nonlinear Relationship between the MJO and ENSO

Cited by 12 publications

References 44 publications

Stable Isotopes of Precipitation During Tropical Sumatra Squalls in Singapore

Stable Isotopes of Precipitation During Tropical Sumatra Squalls in Singapore

Distinct MJOs Under the Two Types of La Niña

On the Annual Variations in the Amplitude of 25-70-Day Intraseasonal Atmospheric Oscillations in Central Africa

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