Three different downstream fates of the boreal-summer MJOs on their passages over the Maritime Continent

Fu, Jinbo; Wang, Wanqiu; Ren, Hong‐Li; Jia, Xiaoyang; Shinoda, Toshiaki

doi:10.1007/s00382-017-3985-2

Cited by 15 publications

(10 citation statements)

References 63 publications

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“…On the lag6 days (Figure 8g), the SC is already covered with the negative velocity potential and OLR anomalies. For 30-90-day ISV (Figure 9), the associated velocity potential anomalies exhibit planetary-scale eastward propagation as has been shown in many previous studies [40][41][42]. Along with the eastward-propagating planetary-scale velocity potential anomalies, the alternative convective-and-suppressed phases move northeastward to modulate the evolutions of the Asian summer monsoon [13,14].…”

Section: Impacts Of Intra-seasonal Variability On the Life-cycle Of T...supporting

confidence: 75%

Objective Identification and Multi-Scale Controlling Factors of Extreme Heat-Wave Events in Southern China

Chen

2020

Atmosphere

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Southern China (SC) is often subjected to the impacts of extreme heat-wave (EHW) events with hot days covering large areas and lasting extended periods in the boreal summer. The present study explores new objective identification methods of the EHW events and reveals the controlling factors of different spatial-temporal variations in shaping the EHW events over SC from 2000 to 2017 with in-situ observations and latest reanalysis. A compound index of the EHW (with impact area, duration, and magnitude) was defined to quantify the overall intensity of the EHW events in SC. It was found that synoptic variability and 10–30-day intra-seasonal variability (ISV) induce the onsets of the EHW events, while 30–90-day ISV shapes the durations. An innovative daily compound index was introduced to track the outbreak of the EHW events. The occurrences of the EHW in SC are coincident with the arrivals of intra-seasonal signals (e.g., the anomalies of outgoing long-wave radiation (OLR) and 500 hPa geopotential height) propagating from the east and south. About 12 days before the onset of the EHW in SC, the 10–30-day positive anomalies of 500 hPa geopotential height and OLR appear near the equatorial western Pacific, which then propagate northwestward to initiate the EHW in SC. At the same time, the 30–90-day suppressed phase propagates northeastward from the Indian Ocean to the SC to sustain the EHW events. On the interannual time scale, it was found that the EHW events in SC occurred in those years with robust warming of the western North Pacific in early summer (May and June) and warming of the equatorial eastern Pacific in the preceding winter (December, January, and February). An interannual sea surface temperature anomalous (SSTA) index, which adds together the SSTA over the above two regions, serves as a very useful seasonal predictor for the EHW occurrences in SC at least one-month ahead.

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Section: Impacts Of Intra-seasonal Variability On the Life-cycle Of T...supporting

confidence: 75%

Objective Identification and Multi-Scale Controlling Factors of Extreme Heat-Wave Events in Southern China

Chen

2020

Atmosphere

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“…Synthesizing the results of Fu et al (2018a) for three boreal-summer MJO types with the ndings of present study, it is noticed that the non-propagating type-II MJO has little to do with the so-called MC barrier effect. During boreal summer, we found that the decaying type-II MJO largely results from the lingering convection over the WNP, which enhances the dry zone over the equatorial WP.…”

Section: A Moisture-budget Perspectivesupporting

confidence: 56%

“…For the type-II, the convection should show continuous eastward-propagation in the IO with at least 30° longitude, but not beyond 125°E (Feng et al 2015;DeMott et al 2018). For the type-III, the contour of -4.5 Wm -2 starts around the MC and propagates eastward to the WP continuously (Hirata et al 2013;Fu et al 2018a). After the second step scrutinization, 114 MJO events are kept with 77, 16, and 21 being the type-I, type-II, and type-III, respectively (The peak dates of all 114 MJO events are given in Table 1 of the supplementary material).…”

Section: 3 the Selection Of Different Mjo Typesmentioning

confidence: 99%

“…Fu et al (2018a) further revealed that a robust Sea-Level-Pressure (SLP) tongue as a Kelvin-wave response to the IO MJO convection(Madden and Julian 1972;Matthews 2000) consistently leads the type-I and type-III, but not the type-II. It is found that, for the type-II, a lingering convection over the western North Paci c (WNP) and a severe dry phase over the equatorial WP block the formation of Kelvin-wave response to the east of the convection, thus halting any further eastward propagation of the type-II MJO.In fact, the type-I and type-II MJOs of Hirata et al (2013) and Fu et al (2018a) are very similar to the propagating and non-propagating MJOs de ned by Kim et al (2014), who emphasized the essential role of a robust dry phase around the MC on the propagating MJO.…”

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confidence: 99%

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Diverse controlling mechanisms and teleconnections of three distinctive MJO types

Liu

Wen

et al. 2022

Clim Dyn

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In present study, three distinctive MJO types in boreal winter are documented and their controlling mechanisms and teleconnections are investigated with a synergetic glocal approach. For the rst time, it is revealed that the diverse nature of the MJO primarily results from different Tropical-Extratropical Interactions and associated internal atmospheric processes. Both the type-I and type-II are initiated over the western Indian Ocean (IO) by a dry zone around the eastern IO, while only the type-I can move out the IO and circulate around the globe. The type-III initiates over the western Paci c (WP) and can circulate the globe and trigger another successive event. The strong upper-level equatorial westerly over the IO-WP, resulting from upstream and extratropical in uences, suffocates the type-II MJO within the IO. On the other hand, the robust upper-level equatorial easterly over the IO-WP, also resulting from upstream and extratropical in uences, along with regional convective instability over the WP and the arrival of east-Asian cold-surge foster the development and eastward propagation of the type-III MJO. The downstream and extratropical teleconnections are primarily controlled by the associated convection over the tropical IO-WP sector for the type-I, but also strongly in uenced by the conditions over the extratropical WP for the type-II and type-III. Given that the MJO has been traditionally viewed as a tropical mode owing its existence to the coupling between organized convection and large-scale circulations, present ndings advocate the MJO as a global mode and call for more research on the involved Tropical-Extratropical Interactions in order to better understand and simulate the diverse nature of the MJO.

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“…All these observational features have been well reproduced by the CGCM (Fig. 1b), although the simulated primary event tends to be characterized by a more westward dispersive group velocity (~ 1 m/s) (Adames and Kim 2016;Chen and Wang 2018b) and an exaggerated "MC propagation barrier" (Zhang and Ling 2017;Fu et al 2018).…”

Section: The Hybrid Coupled Global Climate Modelmentioning

confidence: 68%

Nonlinear optimal moisture perturbations as excitation of primary MJO events in a hybrid coupled climate model

Wei

Ren

et al. 2019

Clim Dyn

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Although the moisture feedback has been well known to be essential in the Madden-Julian Oscillation (MJO) dynamics, whether its pre-moistening effect plays a key role in exciting the onset of primary MJO events, as has been confirmed in the successive initiation, remains elusive. In this study, using a hybrid coupled climate model that has a good fidelity in simulating the intraseasonal variability, we develop a new framework of methodology to investigate the nonlinear excitation of primary MJO event, of which the key achievement is the successful implementation of the conditional nonlinear optimal perturbation (CNOP). In an application of this new framework, the CNOP-type moisture perturbations are calculated for the pre-chosen non-MJO reference states and generally favor a moistening in the equatorial region while drying in the poleward. Comparisons of the model simulation with observation give credibility to the existence of moisture signals several weeks before some primary MJO events. A suite of numerical experiments confirms that the CNOPs of moisture can contribute to the excitation and propagation of strong primary MJO events while random perturbations cannot. The moisture budget analysis further reveals the central importance of the horizontal moisture advection, especially the nonlinearly upscaled moisture transports associated with the high-frequency disturbances on the quasi-3-4-day and 6-8-day synoptic time scales, in supporting the nonlinear excitation of the primary MJO events. The subgrid-scale processes of evaporation, condensation and eddy transport of moisture are found to be critical for the pre-moistening effect in the boundary layer as well. This study directly supports the vital importance of the moisture perturbations, which are characterized by a particular pattern concentrated at low levels, to the nonlinear growth and propagation of the primary MJO events.Publisher's Note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

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Three different downstream fates of the boreal-summer MJOs on their passages over the Maritime Continent

Cited by 15 publications

References 63 publications

Objective Identification and Multi-Scale Controlling Factors of Extreme Heat-Wave Events in Southern China

Objective Identification and Multi-Scale Controlling Factors of Extreme Heat-Wave Events in Southern China

Diverse controlling mechanisms and teleconnections of three distinctive MJO types

Nonlinear optimal moisture perturbations as excitation of primary MJO events in a hybrid coupled climate model

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