Moisture–convection feedback in the tropics

Grabowski, Wojciech W.; Moncrieff, Mitchell W.

doi:10.1256/qj.03.135

Cited by 143 publications

(117 citation statements)

References 65 publications

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“…However, the present result that cloud-radiation interactions are not needed to destabilize the environment is in agreement with (Grabowski, 2003) and (Grabowski and Moncrieff, 2004).…”

Section: Discussionsupporting

confidence: 88%

Testing a cumulus parametrization with a cumulus ensemble model in weak‐temperature‐gradient mode

Raymond

2007

Quart J Royal Meteoro Soc

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This paper prototypes a method for calibrating a cumulus parametrization against a cumulus ensemble model. The key to this technique is to run the cumulus model and the parametrization in identical 'test cells' that provide forcing typical of that seen over tropical oceans. In particular, the mean temperature profile is relaxed to a reference profile that is assumed to be characteristic of the environment of the convection. This is done by calculating the mean vertical velocity needed to balance heating due to convection, latent-heat release, and radiation with adiabatic cooling. This 'weak-temperature-gradient' vertical-velocity profile is then used to advect moisture vertically and, via mass continuity, through the sides of the test cell, entraining reference-profile air as needed.As an example, a toy cumulus parametrization used previously is altered to reproduce the dependence of rainfall rate on surface wind speed shown by the cumulus ensemble model. This alteration greatly changes the behaviour of simulated large-scale disturbances in an aquaplanet equatorial beta-plane model. In particular, increasing the slope of the curve of rainfall rate against wind speed results in the development of much greater synoptic-scale variance.

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“…However, the present result that cloud-radiation interactions are not needed to destabilize the environment is in agreement with (Grabowski, 2003) and (Grabowski and Moncrieff, 2004).…”

Section: Discussionsupporting

confidence: 88%

Testing a cumulus parametrization with a cumulus ensemble model in weak‐temperature‐gradient mode

Raymond

2007

Quart J Royal Meteoro Soc

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“…The important role of synoptic scale wave activity in driving the MJO is documented in a growing body of evidence in the form of observations (28,37,38), simulations (13)(14)(15)(16)(17)23), and theory (18)(19)(20)(21)(22). This synoptic scale wave activity is a complex menagerie of convectively coupled equatorial waves, such as 2-day waves, convectively coupled Kelvin waves, etc.…”

Section: Physical Mechanisms and Basis Of The Modelmentioning

confidence: 99%

“…Nevertheless, they are all interesting theories that contribute to our understanding of certain aspects of the MJO. Other insight has been gained through the study of MJO-like waves in multicloud model simulations (13,14) and in superparameterization computer simulations (15)(16)(17)(18), which appear to capture many of the observed features of the MJO by accounting for smallerscale convective structures within the MJO envelope. The role of convective momentum transport from synoptic scale waves in producing key features of the MJO's planetary scale envelope has also been elucidated by multiscale asymptotic models (19)(20)(21)(22)(23).…”

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confidence: 99%

The skeleton of tropical intraseasonal oscillations

Majda

Stechmann

2009

Proc. Natl. Acad. Sci. U.S.A.

255

211

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The Madden-Julian oscillation (MJO) is the dominant mode of variability in the tropical atmosphere on intraseasonal timescales and planetary spatial scales. Despite the primary importance of the MJO and the decades of research progress since its original discovery, a generally accepted theory for its essential mechanisms has remained elusive. Here, we present a minimal dynamical model for the MJO that recovers robustly its fundamental features (i.e., its "skeleton") on intraseasonal/planetary scales: (i) the peculiar dispersion relation of dω/dk ≈ 0, (ii) the slow phase speed of ≈5 m/s, and (iii) the horizontal quadrupole vortex structure. This is accomplished here in a model that is neutrally stable on planetary scales; i.e., it is tacitly assumed that the primary instabilities occur on synoptic scales. The key premise of the model is that modulations of synoptic scale wave activity are induced by low-level moisture preconditioning on planetary scales, and they drive the "skeleton" of the MJO through modulated heating. The "muscle" of the MJO-including tilts, vertical structure, etc.-is contributed by other potential upscale transport effects from the synoptic scales.Madden-Julian oscillation | convectively coupled equatorial waves | atmospheric convection T he dominant component of intraseasonal variability in the tropics is the 40-to 50-day tropical intraseasonal oscillation, often called the Madden-Julian oscillation (MJO) after its discoverers (1, 2). In the troposphere, the MJO is an equatorial planetary-scale wave envelope of complex multi-scale convective processes. It begins as a standing wave in the Indian Ocean and propagates eastward across the western Pacific Ocean at a speed of ≈5 m/s (3). The planetary-scale circulation anomalies associated with the MJO significantly affect monsoon development, intraseasonal predictability in midlatitudes, and the development of the El Niño southern oscillation (ENSO) in the Pacific Ocean, which is one of the most important components of seasonal prediction (3,4).Despite the widespread importance of the MJO, present-day computer general circulation models (GCMs) typically have poor representations of it (5). A growing body of evidence suggests that this poor performance of GCMs is due to the inadequate treatment of interactions of organized tropical convection on multiple spatiotemporal scales (5, 6). Such hierarchical organized structures that generate the MJO as their envelope are the focus of current observational initiatives and modeling studies (6), and there is a general lack of theoretical understanding of these processes and the MJO itself.A large number of theories have attempted to explain the MJO through mechanisms such as evaporation-wind feedback (7, 8), boundary layer frictional convective instability (9), stochastic linearized convection (10), radiation instability (11), and the planetary-scale linear response to moving heat sources (12). While they all provide some insight into the mechanisms of the MJO, these theories are all at odds with the obse...

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“…In addition to theoretical modeling, various processes and mechanisms have been identified or speculated to play significant roles in MJO dynamics based on numerical model experiences and observations, including shallow convection-BL circulation interaction (Johnson et al 1999;Kikuchi and Takayabu 2004;; stratiform cloud-wave interaction (Mapes 2000;Khouider and Majda 2006;Kuang 2008;Fu and Wang 2009;Seo and Wang 2010;Holloway et al 2013); cloud-radiation interaction (Lee et al 2001;Raymond 2001;Bony and Emanuel 2005;Andersen and Kuang 2012); moisture-convection feedback (Woolnough et al 2001;Grabowski and Moncrieff 2004;Benedict et al 2014), and moisture transport (Maloney 2009;Maloney et al 2010;Andersen and Kuang 2012;Hsu and Li 2012;Kim et al 2014;Pritchard and Bretherton 2014). More details were reviewed by Zhang (2005) and Wang (2005Wang ( , 2012.…”

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confidence: 99%