An MJO-like Gravity Wave and Superclusters Simulated in a Two-Dimensional Cumulus-Scale-Resolving Model under a Warm Pool Condition.

Oouchi, Kazuyoshi; Yamasaki, Masanori

doi:10.2151/jmsj.79.201

Cited by 13 publications

(19 citation statements)

References 85 publications

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“…A way to avoid this difficulty is cumulus convection parameterisation, which was typically subject to uncertainties when implemented in conventional GCMs. The most compelling difficulty is its inability to represent mechanisms associated with mesoscale convection, a key convective element of O (10 km) scale in tropical cyclones (Yamasaki 1986(Yamasaki , 2006 and the MJO (Oouchi and Yamasaki 2001).…”

Section: Introductionmentioning

confidence: 99%

A Simulated Preconditioning of Typhoon Genesis Controlled by a Boreal Summer Madden-Julian Oscillation Event in a Global Cloud-system-resolving Model

Oouchi

Noda

Satoh

et al. 2009

SOLA

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A preconditioning of a typhoon genesis over the North Western Pacific by an Madden-Julian Oscillation (MJO) event is simulated in a boreal summer numerical experiment conducted using a global cloud-systemresolving model. The simulation highlights the importance of the following processes in the typhoon genesis that were not clearly captured in the conventional general circulation models: as the MJO propagates over that region, the easterly shear (with an enhanced lowlevel westerly) of the western branch of the MJO's circulation moderates the climatological westerly shear that is otherwise persistent and inhibits cyclogenesis there. Meanwhile, its attendant cyclonic vorticity from the westerly region migrates northward, causing the genesis to occur. The trough in the upper troposphere at 15° 20°N is found to contribute to the genesis. The result demonstrates the performance of a global cloudsystem-resolving model at predicting tropical cyclogenesis associated with the MJO in the North Western Pacific during the active typhoon season in boreal summer. IntroductionImproving the prediction of tropical cyclogenesis has broad socioeconomic impacts. The need for improvement has been high in the weather forecasting field and will be higher in the future, greenhousewarmed climate condition, when tropical cyclones are projected to become more intense (IPCC 2007) and destructive. Our current understanding of the genesis process remains fragmentary despite the expanded observational network in the tropics after a seminal article (Yanai 1964) on the issue. It was in the past few decades that observational studies suggested a possible link between the MJO, a planetary-scale and quasi-periodic tropical weather event, and statistics of tropical cyclogenesis over some oceanic basins, including the North Western Pacific (Nakazawa 1986).In terms of the modeling approach, both the MJO (Lin et al. 2006) and tropical cyclogenesis are elusive factors. Clouds drive both phenomena, and difficulty in handling a cloud spanning less than the grid spacing of a given model has always hampered our understanding of the phenomena. Atmospheric general circulation models (GCMs) typically use a grid spacing of O (100 km) or so to cover the globe, and the simulated cloud disturbances are too fuzzy to pick up anything as small as a tropical cyclone in the genesis stage and the clouds embedded in an MJO. A way to avoid this difficulty is cumulus convection parameterisation, which was typically subject to uncertainties when implemented in conventional GCMs. The most compelling difficulty is its inability to represent mechanisms associated with mesoscale convection, a key convective element of O (10 km) scale in tropical cyclones (Yamasaki 1986(Yamasaki , 2006) and the MJO (Oouchi and Yamasaki 2001).Alternatively, a "global" cloud-system-resolving model (GCSRM) was suggested. The advent of the Earth Simulator facilitated this computationally intensive calculation. The Nonhydrostatic ICosahedral Atmospheric Model (NICAM) Tomita and Satoh 2004) i...

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Section: Introductionmentioning

confidence: 99%

A Simulated Preconditioning of Typhoon Genesis Controlled by a Boreal Summer Madden-Julian Oscillation Event in a Global Cloud-system-resolving Model

Oouchi

Noda

Satoh

et al. 2009

SOLA

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“…Various computational domain sizes were used in the previous two-dimensional simulations of multi-scale organized convection and associated gravity waves (e.g., Oouchi and Yamasaki 2001;Grabowski and Moncrieff 2001;Liu and Moncrieff 2004;and Tulich et al 2007). We conducted an additional two-dimensional experiment with a doubled horizontal size to test the dependence of the simulated large-scale convective features and attendant waves on the computational domain.…”

Section: Effect Of the Computational Domain Sizementioning

confidence: 99%

“…The multi-scale convective organization and coupled gravity (Kelvin) waves in the tropics has been a topic of several numerical studies (Chao and Lin 1994;Oouchi 1999;Oouchi and Yamasaki 2001;Peng et al 2001;Grabowski and Moncrieff 2001;Liu and Moncrieff 2004;Tulich et al 2007). Using a two-dimensional General Circulation Model (GCM) covering half the globe along the equator, Chao and Lin (1994) successfully simulated two types of convective organizations in easterly basic flow, namely westward-moving cloud clusters and eastward-moving super cloud clusters (envelopes of the cloud clusters).…”

Section: Introductionmentioning

confidence: 99%

“…It was shown that upstream-traveling mesoscale gravity waves originating from existing convection trigger new convection at some distance ahead, and the growing convection, in turn, induces gravity waves which later initiate additional convection farther upstream. This study was later extended by using a computational domain comparable to the equatorial circumference and accounting for the inhomogeneity of SSTs analogous to the tropical western Pacific warm pool (Oouchi and Yamasaki 2001).…”

Section: Introductionmentioning

confidence: 99%

“…Unlike the Oouchi (1999) and Oouchi and Yamasaki (2001) approach of imposing an easterly wind just at the initial state, Grabowski and Moncrieff (2001) and Liu and Moncrieff (2004) adopted a nudging procedure which maintained an easterly background flow throughout the integration. Long-lasting large-scale convective organization was generated in the periodic two-dimensional domain of a few thousand kilometers.…”

Section: Introductionmentioning

confidence: 99%

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Effects of Dimensionality on Simulated Large-Scale Convective Organization and Coupled Waves

Liu

Moncrieff

Hsu

et al. 2012

Journal of the Meteorological Society of Japan

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Tropical multi-scale convective organization of the super-cluster kind and convectively coupled gravity waves are investigated by both two and three-dimensional cloud-system-resolving simulations. The experimental setup includes a constant-temperature ocean surface, constant and horizontally-uniform radiative cooling in the troposphere, and a uniform easterly background wind. The objective of this study is to quantify the impacts of dimensionality on the simulated large-scale convective patterns and associated gravity waves.Eastward propagating large-scale coherent precipitating convection occurs regardless of the spatial dimension. The convective organization has a horizontal wavenumber-one structure in the computational domain and travels at about 13-17 m s −1 relative to the ground, equivalent to 19-23 m s −1 relative to the environmental flow. However, the convectivelyinduced wave signature is much weaker in three dimensions than in two dimensions, as well as a faster translation and a smaller tilt of the vertical. Moreover, a two-dimensional framework generates additional organizational modes compared to the three-dimensional results, including a fast westward-moving system with a mean-flow-relative speed comparable to the eastward-moving wavenumber-1 counterpart and the quasi-stationary (relative to the background flow) higher wavenumber precipitating system. This does not necessarily imply that these additional modes are artifacts of two dimensionality.

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Toward an Understanding of the Madden-Julian Oscillation: With a Mesoscale-Convection-Resolving Model of 0.2 Degree Grid

Yamasaki

2011

Advances in Meteorology

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This paper describes results from numerical experiments which have been performed as the author's first step toward a better understanding of the Madden-Julian oscillation (MJO). This study uses the author's mesoscale-convection-resolving model that was developed in the 1980s to improve parametrization schemes of moist convection. Results from numerical experiments by changing the SST anomaly in the warm pool area indicate that the period of the MJO does not monotonously change with increasing SST anomaly. Between the two extreme cases (no anomaly and strong anomaly), there is a regime in which the period varies in a wide range from 20 to 60 days. In the case of no warm pool, eastward-propagating Kelvin waves are dominant, whereas in the case of a strong warm pool, it produces a quasi-stationary convective system (with pronounced time variation). In a certain regime between the two extreme cases, convective activities with two different properties are strongly interacted, and the period of oscillations becomes complicated. The properties and behaviors of large-scale convective system (LCS), synoptic-scale convective system (SCS), mesoscale convective system (MCS), and mesoscale convection (MC), which constitute the hierarchical structure of the MJO, are also examined. It is also shown that cloud clusters, which constitute the SCS (such as super cloud cluster SCC), consist of a few MCS, and a new MCS forms to the west of the existing MCS. The northwesterly and southwesterly low-level flows contribute to this feature. In view of recent emphasis of the importance of the relative humidity above the boundary layer, it is shown that the model can simulate convective processes that moisten the atmosphere, and the importance of latent instability (positive CAPE), which is a necessary condition for the wave-CISK, is emphasized.

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An MJO-like Gravity Wave and Superclusters Simulated in a Two-Dimensional Cumulus-Scale-Resolving Model under a Warm Pool Condition.

Cited by 13 publications

References 85 publications

A Simulated Preconditioning of Typhoon Genesis Controlled by a Boreal Summer Madden-Julian Oscillation Event in a Global Cloud-system-resolving Model

A Simulated Preconditioning of Typhoon Genesis Controlled by a Boreal Summer Madden-Julian Oscillation Event in a Global Cloud-system-resolving Model

Effects of Dimensionality on Simulated Large-Scale Convective Organization and Coupled Waves

Toward an Understanding of the Madden-Julian Oscillation: With a Mesoscale-Convection-Resolving Model of 0.2 Degree Grid

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