Role of the Boundary Layer Moisture Asymmetry in Causing the Eastward Propagation of the Madden–Julian Oscillation*

Abstract The moisture budget associated with the eastward-propagating Madden–Julian oscillation (MJO) was diagnosed using 1979–2001 40-yr ECMWF Re-Analysis (ERA-40) data. A marked zonal asymmetry of the moisture relative to the MJO convection appears in the planetary boundary layer (PBL, below 700 hPa), creating a potentially more unstable stratification to the east of the MJO convection and favoring the eastward propagation of MJO. The PBL-integrated moisture budget diagnosis indicates that the vertical advection of moisture dominates the low-level moistening ahead of the convection. A further diagnosis indicates that the leading term in the vertical moisture advection is the advection of the background moisture by the MJO ascending flow associated with PBL convergence. The cause of the zonally asymmetric PBL convergence is further examined. It is found that heating-induced free-atmospheric wave dynamics account for 75%–90% of the total PBL convergence, while the warm SST anomaly induced by air–sea interaction contributes 10%–25% of the total PBL convergence. The horizontal moisture advection also plays a role in contributing to the PBL moistening ahead of the MJO convection. The leading term in the moisture advection is the advection across the background moisture gradient by the MJO flow. In the western Indian Ocean, Maritime Continent, and western Pacific, the meridional moisture advection by the MJO northerly flow dominates, while in the eastern Indian Ocean the zonal moisture advection is greater. The contribution of the moisture advection by synoptic eddies is in general small; it has a negative effect over the tropical Indian Ocean and western Pacific and becomes positive in the Maritime Continent region.

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Impacts of the Tropical Pacific–Indian Ocean Associated Mode on Madden–Julian Oscillation over the Maritime Continent in Boreal Winter

Atmosphere ◽

10.3390/atmos11101049 ◽

2020 ◽

Vol 11 (10) ◽

pp. 1049

Author(s):

Xin Li ◽

Ming Yin ◽

Xiong Chen ◽

Minghao Yang ◽

Fei Xia ◽

...

Keyword(s):

Indian Ocean ◽

Kinetic Energy ◽

Tropical Pacific ◽

Western Pacific ◽

Boreal Summer ◽

Boreal Winter ◽

Madden Julian Oscillation ◽

Maritime Continent ◽

The Western Pacific ◽

The Tropical Pacific

Based on the observation and reanalysis data, the relationship between the Madden–Julian Oscillation (MJO) over the Maritime Continent (MC) and the tropical Pacific–Indian Ocean associated mode was analyzed. The results showed that the MJO over the MC region (95°–150° E, 10° S–10° N) (referred to as the MC–MJO) possesses prominent interannual and interdecadal variations and seasonally “phase-locked” features. MC–MJO is strongest in the boreal winter and weakest in the boreal summer. Winter MC–MJO kinetic energy variation has significant relationships with the El Niño–Southern Oscillation (ENSO) in winter and the Indian Ocean Dipole (IOD) in autumn, but it correlates better with the tropical Pacific–Indian Ocean associated mode (PIOAM). The correlation coefficient between the winter MC–MJO kinetic energy index and the autumn PIOAM index is as high as −0.5. This means that when the positive (negative) autumn PIOAM anomaly strengthens, the MJO kinetic energy over the winter MC region weakens (strengthens). However, the correlation between the MC–MJO convection and PIOAM in winter is significantly weaker. The propagation of MJO over the Maritime Continent differs significantly in the contrast phases of PIOAM. During the positive phase of the PIOAM, the eastward propagation of the winter MJO kinetic energy always fails to move across the MC region and cannot enter the western Pacific. However, during the negative phase of the PIOAM, the anomalies of MJO kinetic energy over the MC is not significantly weakened, and MJO can propagate farther eastward and enter the western Pacific. It should be noted that MJO convection is more likely to extend to the western Pacific in the positive phases of PIOAM than in the negative phases. This is significant different with the propagation of the MJO kinetic energy.

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Impact of the Madden–Julian Oscillation on Summer Rainfall in Southeast China

Journal of Climate ◽

10.1175/2008jcli1959.1 ◽

2009 ◽

Vol 22 (2) ◽

pp. 201-216 ◽

Cited By ~ 62

Author(s):

Lina Zhang ◽

Bizheng Wang ◽

Qingcun Zeng

Keyword(s):

Indian Ocean ◽

Tropical Indian Ocean ◽

Summer Rainfall ◽

Western Pacific ◽

Madden Julian Oscillation ◽

Energy Propagation ◽

Southeast China ◽

The Indian Ocean ◽

The Impact ◽

The Western Pacific

Abstract The impact of the Madden–Julian oscillation (MJO) on summer rainfall in Southeast China is investigated using the Real-time Multivariate MJO (RMM) index and the observational rainfall data. A marked transition of rainfall patterns from being enhanced to being suppressed is found in Southeast China (east of 105°E and south of 35°N) on intraseasonal time scales as the MJO convective center moves from the Indian Ocean to the western Pacific Ocean. The maximum positive and negative anomalies of regional mean rainfall are in excess of 10% relative to the climatological regional mean. Such different rainfall regimes are associated with the corresponding changes in physical fields such as the western Pacific subtropical high (WPSH), moisture, and vertical motions. When the MJO is mainly over the Indian Ocean, the WPSH shifts farther westward, and the moisture and upward motions in Southeast China are increased. In contrast, when the MJO enters the western Pacific, the WPSH retreats eastward, and the moisture and upward motions in Southeast China are decreased. It is suggested that the MJO may influence summer rainfall in Southeast China through remote and local dynamical mechanisms, which correspond to the rainfall enhancement and suppression, respectively. The remote role is the energy propagation of the Rossby wave forced by the MJO-related heating over the Indian Ocean through the low-level westerly waveguide from the tropical Indian Ocean to Southeast China. The local role is the northward shift of the upward branch of the anomalous meridional circulation when the MJO is over the western Pacific, which causes eastward retreat of the WPSH and suppressed moisture transport toward Southeast China.

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Oceanic Impetus for Convective Onset of the Madden–Julian Oscillation in the Western Indian Ocean

Journal of Climate ◽

10.1175/jcli-d-16-0595.1 ◽

2017 ◽

Vol 30 (11) ◽

pp. 4299-4316 ◽

Cited By ~ 11

Author(s):

Adam V. Rydbeck ◽

Tommy G. Jensen

Keyword(s):

Boundary Layer ◽

Indian Ocean ◽

Atmospheric Boundary Layer ◽

Rossby Waves ◽

Deep Convection ◽

Western Indian Ocean ◽

Convection Boundary Layer ◽

Madden Julian Oscillation ◽

Sst Gradient ◽

Equatorial Rossby Waves

Abstract A theory for intraseasonal atmosphere–ocean–atmosphere feedback is supported whereby oceanic equatorial Rossby waves are partly forced in the eastern Indian Ocean by the Madden–Julian oscillation (MJO), reemerge in the western Indian Ocean ~70 days later, and force large-scale convergence in the atmospheric boundary layer that precedes MJO deep convection. Downwelling equatorial Rossby waves permit high sea surface temperature (SST) and enhance meridional and zonal SST gradients that generate convergent circulations in the atmospheric boundary layer. The magnitude of the SST and SST gradient increases are 0.25°C and 1.5°C Mm−1 (1 megameter is equal to 1000 km), respectively. The atmospheric circulations driven by the SST gradient are estimated to be responsible for up to 45% of the intraseasonal boundary layer convergence observed in the western Indian Ocean. The SST-induced boundary layer convergence maximizes 3–4 days prior to the convective maximum and is hypothesized to serve as a trigger for MJO deep convection. Boundary layer convergence is shown to further augment deep convection by locally increasing boundary layer moisture. Warm SST anomalies facilitated by downwelling equatorial Rossby waves are also associated with increased surface latent heat fluxes that occur after MJO convective onset. Finally, generation of the most robust downwelling equatorial Rossby waves in the western Indian Ocean is shown to have a distinct seasonal distribution.

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ANALISIS PENGARUH MADDEN JULIAN OSCILLATION (MJO) TERHADAP ANOMALI CURAH HUJAN DI WILAYAH NGURAH RAI

Jurnal Meteorologi Klimatologi dan Geofisika ◽

10.36754/jmkg.v6i2.123 ◽

2019 ◽

Vol 6 (2) ◽

pp. 49-55

Author(s):

Wendel Jan Pattipeilohy ◽

Femmy Marsitha B ◽

Devina Putri Asri

Keyword(s):

Indian Ocean ◽

Western Pacific ◽

Madden Julian Oscillation ◽

Maritime Continent

Madden Julian Oscillation (MJO) merupakan suatu gelombang atau osilasi non seasonal yang terjadi di lapisan troposfer yang bergerak dari barat ke timur dengan periode osilasi kurang lebih 30-60 hari. Fenomena ini sangat berdampak terhadap kondisi anomali curah hujan pada suatu wilayah yang dilaluinya. Dalam penelitian ini delapan fase MJO dikelompokan menjadi 4 bagian sesuai dengan pergerakannya yaitu fase 1 dan 8 (Western and Africa), fase 2 dan 3 (Indian Ocean), fase 4 dan 5 (Maritime Continent), fase 6 dan 7 (Western Pacific). Data yang digunakan dalam penelitian ini yaitu data curah hujan periode 1996-2015 dan data MJO periode yang sama. Lokasi penelitian yaitu wilayah Ngurah Rai. Data curah hujan dihitung anomalinya lalu dipisahkan antara anomali positif dan negatif lalu disandingkan dengan fase MJO aktif. Penelitian ini bertujuan untuk menganalisis porsentase kelompok fase MJO mana yang mendominasi anomali curah hujan pada saat anomali positif maupun negatif. Hasil kajian menunjukan persentase kejadian anomali curah hujan positif dominan terjadi saat fase MJO berada di Maritime Continent sebesar 36%. Kemudian persentase kejadian anomali curah hujan negatif dominan terjadi saat MJO berada pada fase Indian Ocean dengan porsentasi sebesar 33%.

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Seasonality and Dynamics of Atmospheric Teleconnection from the Tropical Indian Ocean and the Western Pacific to West Antarctica

Atmosphere ◽

10.3390/atmos12070849 ◽

2021 ◽

Vol 12 (7) ◽

pp. 849

Author(s):

Hyun-Ju Lee ◽

Emilia-Kyung Jin

Keyword(s):

Indian Ocean ◽

Rossby Wave ◽

Tropical Indian Ocean ◽

Western Pacific ◽

Tropical Region ◽

Formation Mechanisms ◽

West Antarctica ◽

Background Flow ◽

The Impact ◽

The Western Pacific

The global impact of the tropical Indian Ocean and the Western Pacific (IOWP) is expected to increase in the future because this area has been continuously warming due to global warming; however, the impact of the IOWP forcing on West Antarctica has not been clearly revealed. Recently, ice loss in West Antarctica has been accelerated due to the basal melting of ice shelves. This study examines the characteristics and formation mechanisms of the teleconnection between the IOWP and West Antarctica for each season using the Rossby wave theory. To explicitly understand the role of the background flow in the teleconnection process, we conduct linear baroclinic model (LBM) simulations in which the background flow is initialized differently depending on the season. During JJA/SON, the barotropic Rossby wave generated by the IOWP forcing propagates into the Southern Hemisphere through the climatological northerly wind and arrives in West Antarctica; meanwhile, during DJF/MAM, the wave can hardly penetrate the tropical region. This indicates that during the Austral winter and spring, the IOWP forcing and IOWP-region variabilities such as the Indian Ocean Dipole (IOD) and Indian Ocean Basin (IOB) modes should paid more attention to in order to investigate the ice change in West Antarctica.

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Acetone and acetonitrile in the tropical Indian Ocean boundary layer and free troposphere: Aircraft-based intercomparison of AP-CIMS and PTR-MS measurements

Journal of Geophysical Research Atmospheres ◽

10.1029/2000jd900599 ◽

2001 ◽

Vol 106 (D22) ◽

pp. 28511-28527 ◽

Cited By ~ 39

Author(s):

Detlev Sprung ◽

Christof Jost ◽

Thomas Reiner ◽

Armin Hansel ◽

Armin Wisthaler

Keyword(s):

Boundary Layer ◽

Indian Ocean ◽

Tropical Indian Ocean ◽

Free Troposphere ◽

Ocean Boundary

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The identity of Pilumnoplax acanthomerus Rathbun, 1911 (Crustacea: Decapoda: Brachyura: Xanthidae), with new records from the central and western Pacific

Zootaxa ◽

10.11646/zootaxa.3367.1.20 ◽

2012 ◽

Vol 3367 (1) ◽

pp. 211 ◽

Cited By ~ 2

Author(s):

JOSE CHRISTOPHER E. MENDOZA ◽

PAUL F. CLARK ◽

PETER K. L. NG

Keyword(s):

Indian Ocean ◽

New Genus ◽

New Records ◽

Western Indian Ocean ◽

Morphological Characters ◽

Western Pacific ◽

Monotypic Genus ◽

Central Pacific ◽

Western Atlantic ◽

Line Islands

The identity of the rare xanthid crab, Pilumnoplax acanthomerus Rathbun, 1911, originally described from the AmiranteIslands in the western Indian Ocean, is elucidated. Števčić (2005) transferred the species from Pilumnoplax Stimpson,1858, to a new genus, Linnaeoxantho. This monotypic genus is re-diagnosed and new morphological characters are high-lighted. New records from Ryukyu and Line Islands, in the western and central Pacific, respectively, are reported. Linnae-oxantho is compared with the morphologically similar Melybia Stimpson, 1871, from the western Atlantic, and theiraffinities are discussed. Linnaeoxanthinae Števčić, 2005, is here recognised as a valid xanthid subfamily for Linnaeoxantho and Melybia, and is considered to have priority over Melybiidae Števčić, 2005.

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Impacts of atmospheric and oceanic initial conditions on boreal summer intraseasonal oscillation forecast in the BCC model

Theoretical and Applied Climatology ◽

10.1007/s00704-020-03312-2 ◽

2020 ◽

Vol 142 (1-2) ◽

pp. 393-406

Author(s):

Zhongkai Bo ◽

Xiangwen Liu ◽

Weizong Gu ◽

Anning Huang ◽

Yongjie Fang ◽

...

Keyword(s):

Indian Ocean ◽

North Pacific ◽

Western North Pacific ◽

Initial Conditions ◽

Intraseasonal Oscillation ◽

Tropical Indian Ocean ◽

Boreal Summer ◽

Model Errors ◽

Maritime Continent ◽

Boreal Summer Intraseasonal Oscillation

Abstract In this paper, we evaluate the capability of the Beijing Climate Center Climate System Model (BCC-CSM) in simulating and forecasting the boreal summer intraseasonal oscillation (BSISO), using its simulation and sub-seasonal to seasonal (S2S) hindcast results. Results show that the model can generally simulate the spatial structure of the BSISO, but give relatively weaker strength, shorter period, and faster transition of BSISO phases when compared with the observations. This partially limits the model’s capability in forecasting the BSISO, with a useful skill of only 9 days. Two sets of hindcast experiments with improved atmospheric and atmosphere/ocean initial conditions (referred to as EXP1 and EXP2, respectively) are conducted to improve the BSISO forecast. The BSISO forecast skill is increased by 2 days with the optimization of atmospheric initial conditions only (EXP1), and is further increased by 1 day with the optimization of both atmospheric and oceanic initial conditions (EXP2). These changes lead to a final skill of 12 days, which is comparable to the skills of most models participated in the S2S Prediction Project. In EXP1 and EXP2, the BSISO forecast skills are improved for most initial phases, especially phases 1 and 2, denoting a better description for BSISO propagation from the tropical Indian Ocean to the western North Pacific. However, the skill is considerably low and insensitive to initial conditions for initial phase 6 and target phase 3, corresponding to the BSISO convection’s active-to-break transition over the western North Pacific and BSISO convection’s break-to-active transition over the tropical Indian Ocean and Maritime Continent. This prediction barrier also exists in many forecast models of the S2S Prediction Project. Our hindcast experiments with different initial conditions indicate that the remarkable model errors over the Maritime Continent and subtropical western North Pacific may largely account for the prediction barrier.

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Precursor Environmental Conditions Associated with the Termination of Madden–Julian Oscillation Events

Journal of the Atmospheric Sciences ◽

10.1175/jas-d-14-0254.1 ◽

2015 ◽

Vol 72 (5) ◽

pp. 1908-1931 ◽

Cited By ~ 12

Author(s):

Justin P. Stachnik ◽

Duane E. Waliser ◽

Andrew J. Majda

Keyword(s):

Indian Ocean ◽

Environmental Conditions ◽

Warm Pool ◽

Western Pacific ◽

Specific Humidity ◽

Advection Equation ◽

Local Domain ◽

Madden Julian Oscillation ◽

Budget Analysis ◽

The Indian Ocean

Abstract This study presents an analysis of the precursor environmental conditions related to the termination of Madden–Julian oscillation (MJO) events. A simple climatology is created using a real-time MJO monitoring index, documenting the locations and frequencies of MJO decay. Lead–lag composites of several atmospheric variables including temperature, moisture, and intraseasonal wind anomalies are generated from three reanalyses. There is remarkable agreement among the datasets with long-term, lower-tropospheric moisture deficits over the local domain best identifying termination events over the Indian Ocean. MJO termination in the Indian Ocean is also linked to a northward shift of the intertropical convergence zone (ITCZ) with possible lead times as much as 20 days prior to MJO decay. Statistically significant differences in the low-level vertical velocity and specific humidity are also identified more than 10 days in advance of MJO termination events in the western Pacific, though the differences here are more symmetric about the equator. Unlike the Indian Ocean and western Pacific, MJOs that terminate over the Maritime Continent appear to be related to their own intensity rather than the downstream conditions. As such, only the strongest MJOs tend to propagate into the warm pool region. Finally, a budget analysis is performed on the three-dimensional moisture advection equation in order to better elucidate what time scales and physical mechanisms are most important for MJO termination. The combination of intraseasonal vertical circulation anomalies coupled with the mean-state specific humidity best explain the anomalous moisture patterns associated with MJO termination, suggesting that the downstream influence of the MJO circulation can eventually lead to its future demise.

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