Some Climatological Aspects of the Madden–Julian Oscillation (MJO)

Lafleur, Donald M.; Barrett, Bradford S.; Henderson, Gina R.

doi:10.1175/jcli-d-14-00744.1

Cited by 61 publications

(64 citation statements)

References 77 publications

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“…These anomalies were then correlated with z500 height anomalies for each SOM node. Approximately 56% of days featured active MJO, and approximately 44% of those days were inactive (Figure ), statistics supported by the MJO climatology of LaFleur et al (). Among the eight active phases, days were somewhat unevenly distributed amongst MJO phases 1–8, where phases 5 and 1 occurred most often (Figure ), with approximately 12 and 8% relative frequency (Figure ), while phases 3 and 7 occurred least often (Figure ), each with approximately 5% of the days in the period (Figure ).…”

Section: Resultssupporting

confidence: 61%

Eurasian October snow water equivalent: using self‐organizing maps to characterize variability and identify relationships to the MJO

Henderson

Barrett

South

2016

Intl Journal of Climatology

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Variability in October daily snow water equivalent (SWE) change using self‐organizing maps (SOMs) was explored in this study. In addition, connections between October Eurasian daily snow water equivalent change (ΔSWE) and the leading mode of atmospheric intra‐seasonal variability, the Madden–Julian Oscillation (MJO), were considered. Through this analysis, dipole and tripole patterns of daily ΔSWE over Eurasia were identified and were moderately negatively correlated to mid‐tropospheric geopotential height anomalies. Additionally, SOM nodes capturing over 91% of October days were found moderately correlated with at least one MJO phase. The majority of correlation coefficients with magnitude above 0.30 were found for MJO phases 4–7, indicating that tropical convective anomalies over the Indian Ocean and Maritime Continent have the most impact on October circulation and snow variability. Furthermore, MJO phases with above‐normal frequency were most often found in SOM nodes with positive correlations between their respective 500‐hPa height anomalies, while MJO phases with below‐normal frequency were most often found in SOM nodes with negative correlations between their respective 500‐hPa height anomalies. These correlation patterns provide additional evidence linking the MJO to Eurasian snow variability. These results highlight a new application of SOMs in identifying snow variability throughout Eurasia during the month of October, in addition to providing evidence for tropical modulation of the extratropics on the intra‐seasonal timescale.

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Section: Resultssupporting

confidence: 61%

Eurasian October snow water equivalent: using self‐organizing maps to characterize variability and identify relationships to the MJO

Henderson

Barrett

South

2016

Intl Journal of Climatology

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“…In general, MJO-related convection appears more frequently over the western Pacific during boreal winter (Lafleur et al, 2015). However, the occurrence of MJO-related convection is relatively high (nearly 35%) over the Indian Ocean (phases 2 and 3), while it is low (only 18%) over the Maritime Continent (phases 4 and 5) during EP El Niño.…”

Section: Summary and Discussionmentioning

confidence: 92%

Impacts of two types of El Niño on the MJO during boreal winter

et al. 2016

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The features of the MJO during two types of El Niño events are investigated in this paper using the daily NCEP-2 reanalysis data, OLR data from NOAA, and Real-time Multivariate MJO index for the period 1979-2012. The results indicate that the MJO exhibits distinct features during eastern Pacific (EP) El Niño events, as compared to central Pacific (CP) El Niño events. First, the intensity of the MJO is weakened during EP El Niño winters from the tropical eastern Indian Ocean to the western Pacific, but enhanced during CP El Niño winters. Second, the range of the MJO eastward propagation is different during the two types of El Niño events. During EP El Niño winters, the MJO propagates eastwards to 120 • W, but only to 180 • during CP El Niño winters. Finally, the frequency in eight phases of the MJO may be affected by the two types of El Niño. Phases 2 and 3 display a stronger MJO frequency during EP El Niño winters, but phases 4 and 5 during CP El Niño winters.

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“…The 74 MJOs available for investigation during 1998–2013 range from weak to strong (RMM amplitude = 0.5–2.5), less rainy to heavily precipitating (maximum rain rates of 5–35 mm d −1 ), and short to long‐lasting events (RMM duration = 20–80 days). The life cycle of these MJOs (20–80 day) is consistent with MJO's climatological variability [ Lafleur et al ., ]. Therefore, this study is not biased to a particular type of MJO event but captures the broad variability documented by many previous studies.…”

Section: Resultsmentioning

confidence: 99%

Time scales of shallow‐to‐deep convective transition associated with the onset of Madden‐Julian Oscillations

Rutledge

2016

Geophysical Research Letters

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This study statistically investigates the timing and underlying processes of the shallow‐to‐deep convective transition (SDT) associated with Madden‐Julian Oscillations (MJO) initiation over the Indian Ocean. Results show that SDT periods have a median value of 8–10 days with a wide spectrum of 2–20 days. SDTs lasting 10–20 days occurred nearly 50% of the time, consistent with gradual tropospheric moistening and destabilization leading to MJO initiation as described by the discharge‐recharge theory. Rapid SDTs (<7 days) took place in 25% of the MJOs studied, including two MJOs observed during Dynamics of the MJO in which previous studies suggested large‐scale moistening dominates the local convective moistening during SDT. SDT length is only weakly correlated to MJO amplitude and duration defined by the Real‐Time Multivariate MJO index. SDT length is negatively correlated with the duration of the shallow convective period preceding the SDT but weakly correlated with individual parameters associated with preonset environments.

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Some Climatological Aspects of the Madden–Julian Oscillation (MJO)

Cited by 61 publications

References 77 publications

Eurasian October snow water equivalent: using self‐organizing maps to characterize variability and identify relationships to the MJO

Eurasian October snow water equivalent: using self‐organizing maps to characterize variability and identify relationships to the MJO

Impacts of two types of El Niño on the MJO during boreal winter

Time scales of shallow‐to‐deep convective transition associated with the onset of Madden‐Julian Oscillations

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