Three-Dimensional Structure and Evolution of the Moisture Field in the MJO

Adames, Ángel F.; Wallace, John M.

doi:10.1175/jas-d-15-0003.1

Cited by 93 publications

(108 citation statements)

References 60 publications

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“…The terms on the right-hand side are the horizontal moisture advection term (Hadv), vertical moisture advection term (Vadv), and apparent moisture sink term (−Q 2 ), respectively. These tilting features are consistent with previous findings (e.g., Adames & Wallace, 2015a;Hsu & Li, 2012;Sperber, 2003). The anomalous moisture structure and budget terms are all regressed to the index of nontraditional filtered intraseasonal precipitation anomalies averaged over the equatorial eastern Indian Ocean (EIO; 10°S to 10°N, 80-100°E) because the MJO convection and circulation over the IO are more symmetric about the equator and less affected by climatological circulations.…”

Section: Moisture Budget and Structuresupporting

confidence: 85%

Effects of Moisture Initialization on MJO and its Teleconnection Prediction in BCC Subseasonal Coupled Model

Ren

Lü

et al. 2020

JGR Atmospheres

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It is well recognized that moisture is of great importance in the representation of the Madden-Julian Oscillation (MJO). In this study, a moisture initialization scheme is developed using the Beijing Climate Center (BCC) subseasonal operational coupled model, and its effects on MJO predictions are investigated. Three sets of hindcast experiments are conducted: a reference experiment without moisture initialization (REF) and two sensitivity experiments with moderate and strong moisture nudging schemes. We show that the prediction skill of the real-time multivariate MJO index is significantly improved in the two sensitivity experiments, where the skillful prediction can reach up to 20 days using the moderate nudging scheme. Larger improvements can be achieved when MJO was initiated from Phases 2-3 and 5-7 or during La Niña episodes, implying that the MJO prediction skill is more sensitive to moisture conditions in active convection regions and backgrounds. The moisture budget analysis indicated that the MJO prediction improvement using the moisture initialization schemes comes from the realistic representation of vertical moisture structure and vertical moisture advection to the east of the MJO convection in the planetary boundary layer. The improved MJO prediction is also demonstrated to enable a more reliable subseasonal prediction of extratropical circulation and precipitation through a more realistic description of MJO-related teleconnections. In addition, the ensemble mean of the three schemes can extend the MJO prediction skill to more than 22 days, showing the potential benefits of ensemble prediction of multiinitialization schemes.

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Section: Moisture Budget and Structuresupporting

confidence: 85%

Effects of Moisture Initialization on MJO and its Teleconnection Prediction in BCC Subseasonal Coupled Model

Ren

Lü

et al. 2020

JGR Atmospheres

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“…Within the MJO, MSE tendencies are dominated by HADV, (cf. Maloney, ), which is dominated by midlevel moisture advection (Adames & Wallace, ; DeMott et al, ). Some of our analyses, therefore, use specific humidity integrated from 850 to 500 hPa (i.e., 〈 q 〉 850–500 ) to interpret MSE HADV.…”

Section: Methodsmentioning

confidence: 99%

“…A plethora of characteristics have been noted for MC‐crossing and non‐MC‐crossing events. For example, MC‐crossing MJO events feature anomalous dry conditions to the east of MJO convection (Kim et al, ), enhanced eastward and equatorward moisture gradients in the vicinity of the MC (Gonzalez & Jiang, ; Kim et al, ), and moist preconditioning by low‐level horizontal moisture advection (Adames & Wallace, ; Kiranmayi & Maloney, ; Maloney, , and many others). Non‐MC‐crossing MJO events exhibit weak or nonexistent dry phases east of MJO convection (Kim et al, ), a lack of low‐level moistening by horizontal and vertical moisture advection (Hsu & Li, ), seasonal and interannual variability (Kerns & Chen, ), and a lack of convection over the Indonesian Seas (Zhang & Ling, ).…”

Section: Introductionmentioning

confidence: 99%

Atmospheric Mechanisms for MJO Decay Over the Maritime Continent

et al. 2018

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Eastward propagating Madden‐Julian oscillation (MJO) events that develop in the Indian Ocean from November to April are separated into events whose convective anomalies do and do not propagate across the Maritime Continent (MC). Propagating (P) events are divided into strong (sP) and weak (wP) subsets based on the initial amplitudes of their convective anomalies. Eastward decaying (ED) MJO events have initial amplitudes similar to those of wP events. Roughly half of all MJO events encounter westward propagating transient dry precursor (TDP) signals over the MC. These TDPs, which are external to the MJO circulation system, overwhelm the weak, eastward propagating moist anomaly in ED events, leading to MJO termination. In wP events, the MJO moist anomaly is stronger than the TDP dry anomaly, and the MJO propagates beyond the MC. ED MJO events that do not encounter TDPs decay because of insufficient moistening in the southern MC region. The background states of TDP‐ and non‐TDP‐affected MJO events resemble La Niña and El Niño conditions, respectively. The regional regulation of TDP activity and background moisture gradients by El Niño–Southern Oscillation can both be understood in terms of the zonal shift and the meridional expansion or contraction of Warm Pool moisture in response to El Niño–Southern Oscillation sea surface temperature anomalies. Our results demonstrate that modulation of TDPs by the background state moisture can affect the MJO in a manner that reinforces its propagation or decay via the interaction of MJO circulation anomalies and background moisture gradients.

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“…Because the MJO is a propagating system, there is merit to inspecting the eastward propagating systems in a Lagrangian perspective (Adames & Wallace, ). To do this, we implemented an approach hinged on the expansion and contraction of the eastern and subsiding branch of the Indian Ocean zonal overturning circulation cell (eastern edge of the dashed contour cell in Figure ).…”

Section: Data Methods and Approachmentioning

confidence: 99%

Moist Entropy and Water Isotopologues in a Zonal Overturning Circulation Framework of the Madden‐Julian Oscillation

et al. 2019

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The Madden‐Julian oscillation (MJO) is the principal source of tropical intraseasonal variability, yet challenges remain to accurately simulate its observed convective behavior and eastward propagation. There is specific need for evaluating the role of water within the MJO, including evaporation, vertical transport, precipitation, and latent heating of the coupled atmosphere‐ocean system. Hydrogen isotope ratios are particularly useful for investigating these aspects of the water cycle. This study complements previous characterization of MJO joint distributions for water vapor and isotopologue concentrations (δD) with consideration of moist entropy in the tropical zonal overturning circulation framework of the MJO. The goals are to distinguish the roles of convective and large‐scale dynamic processes through the life cycle of the MJO and identify shortcomings for modeling MJO humidity, clouds, and convection. From MJO composite analyses, wet equivalent potential temperature (θq) anomalies are largest at 500 hPa and tilt westward with altitude. A positive θq anomaly co‐occurs with the precipitation maxima, and negative θq anomalies co‐occur with subsidence both trailing and leading the convective center. Out of phase with θq, δD anomalies are positive east and negative west of the convective center, coherent with the regional zonal overturning stream function. These results point to a decoupling in the MJO between midtroposphere water vapor, which is tied to convective processes, and the isotopologue ratios, which are tied to the large‐scale circulation. A conceptual model is presented to describe the physical processes that explain the MJO life‐cycle for joint distributions of humidity (q) and water vapor δD.

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Three-Dimensional Structure and Evolution of the Moisture Field in the MJO

Cited by 93 publications

References 60 publications

Effects of Moisture Initialization on MJO and its Teleconnection Prediction in BCC Subseasonal Coupled Model

Effects of Moisture Initialization on MJO and its Teleconnection Prediction in BCC Subseasonal Coupled Model

Atmospheric Mechanisms for MJO Decay Over the Maritime Continent

Moist Entropy and Water Isotopologues in a Zonal Overturning Circulation Framework of the Madden‐Julian Oscillation

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