Upscale effects in simulations of tropical convection on an equatorial beta-plane

Shutts, G. J.

doi:10.1016/j.dynatmoce.2006.02.006

Cited by 12 publications

(9 citation statements)

References 26 publications

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“…The westerly momentum sink in the regions of the subtropical jets due to the eddies is important in the angular momentum budget of the Hadley Cells, reducing the jet speeds far below those implied by angular momentum conservation. Recently, Shutts (2006) has emphasised the sensitivity of the Hadley Cell circulations in equatorial β-plane simulations to the magnitude of momentum sink imposed in his model. Lorenz (1955) quantified both the thermal and mechanical impacts of eddies on the zonally averaged flow in his global energy cycle of Available Potential Energy and Kinetic Energy.…”

Section: Historical and Theoretical Contextmentioning

confidence: 99%

“…These studies have found a "self-aggregation" of deep convection into one or more clusters that depends on cloud radiative and/or surface flux feedbacks. In the work mentioned above, Shutts (2006) used a form of CSRM on an equatorial β-plane aquaplanet with varying SST to investigate the large scale tropical circulation.…”

Section: The Conceptual Role Of Aqua-planet Configurationsmentioning

confidence: 99%

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Context and Aims of the Aqua-Planet Experiment

Blackburn

Hoskins

2013

Journal of the Meteorological Society of Japan

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The Aqua-Planet Experiment (APE) was first proposed by Neale and Hoskins (2000a) as a benchmark for atmospheric general circulation models (AGCMs) on an idealised water-covered Earth. The experiment and its aims are summarised, and its context within a modelling hierarchy used to evaluate complex models and to provide a link between realistic simulation and conceptual models of atmospheric phenomena is discussed. The simplified aqua-planet configuration bridges a gap in the existing hierarchy. It is designed to expose differences between models and to focus attention on particular phenomena and their response to changes in the underlying distribution of sea surface temperature.Keywords comparison of atmospheric general circulation models (GCMs); modelling hierarchy; tropical circulation; intertropical convergence zone (ITCZ); precipitation APE is intended to be one component of a modelling hierarchy -a hierarchy of increasing complexity, of the models themselves and of the experimental configuration to which they are applied. The hierarchy has two distinct but overlapping roles. On the one hand it provides a suite of benchmark experiments to test complex models and their components. This can be considered an evaluation framework. On the other hand it provides a link between theory, observation and complex models in meteorology, the need for which has been stressed by Hoskins (1983) andHeld (2005). This can be considered a conceptual framework. Without the full range of models, from the simple 'back-ofthe-envelope' models to the complex, state-of-the-art, computer intensive models, theory tends to proceed with little contact with data from the real atmosphere and results from complex models. In consequence, the framework for interpreting observations and the results from complex models, and also for improving the

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Section: Historical and Theoretical Contextmentioning

confidence: 99%

Section: The Conceptual Role Of Aqua-planet Configurationsmentioning

confidence: 99%

Context and Aims of the Aqua-Planet Experiment

Blackburn

Hoskins

2013

Journal of the Meteorological Society of Japan

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“…This framework has also shown improvement in the MJO (or in MJO-like variability in aquaplanet configurations) for both atmosphere-only simulations (Grabowski 2003;Benedict and Randall 2009) and especially for coupled oceanatmosphere simulations (Benedict and Randall 2011). In a limited-area (although zonally periodic) framework, Shutts (2006) and Shutts (2008) find persistent eastward-propagating large-scale precipitation clusters in an equatorial beta-plane simulation of tropical convection using explicit convection on an anisotropic grid with 1-km spacing in the zonal direction and 40-km spacing in the meridional direction.…”

Section: Introductionmentioning

confidence: 99%

The Effects of Explicit versus Parameterized Convection on the MJO in a Large-Domain High-Resolution Tropical Case Study. Part I: Characterization of Large-Scale Organization and Propagation*

Holloway

Woolnough

Lister

2013

Journal of the Atmospheric Sciences

114

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High-resolution simulations over a large tropical domain (;208S-208N, 428E-1808) using both explicit and parameterized convection are analyzed and compared to observations during a 10-day case study of an active Madden-Julian oscillation (MJO) event. The parameterized convection model simulations at both 40-and 12-km grid spacing have a very weak MJO signal and little eastward propagation. A 4-km explicit convection simulation using Smagorinsky subgrid mixing in the vertical and horizontal dimensions exhibits the best MJO strength and propagation speed. Explicit convection simulations at 12 km also perform much better than the 12-km parameterized convection run, suggesting that the convection scheme, rather than horizontal resolution, is key for these MJO simulations. Interestingly, a 4-km explicit convection simulation using the conventional boundary layer scheme for vertical subgrid mixing (but still using Smagorinsky horizontal mixing) completely loses the large-scale MJO organization, showing that relatively high resolution with explicit convection does not guarantee a good MJO simulation. Models with a good MJO representation have a more realistic relationship between lower-free-tropospheric moisture and precipitation, supporting the idea that the moisture-convection feedback is a key process for MJO propagation. There is also increased generation of available potential energy and conversion of that energy into kinetic energy in models with a more realistic MJO, which is related to larger zonal variance in convective heating and vertical velocity, larger zonal temperature variance around 200 hPa, and larger correlations between temperature and ascent (and between temperature and diabatic heating) between 500 and 400 hPa.

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“…Cloud-resolving models (CRMs) have been used by a number of investigators as tools for studying tropical convective wave variability (e.g., Oouchi 1999;Grabowski and Moncrieff 2001;Peng et al 2001;Tomita et al 2005;Peters and Bretherton 2006;Shutts 2006;Tulich et al 2007, hereafter TRM07). Invariably, these studies find that large-scale convective wave envelopes (with embedded smaller-scale wave disturbances) tend to develop spontaneously under spatially uniform radiative cooling and zonally uniform sea surface temperatures (SSTs).…”

Section: Introductionmentioning

confidence: 99%

Multiscale Convective Wave Disturbances in the Tropics: Insights from a Two-Dimensional Cloud-Resolving Model

Tulich

Mapes

2008

Journal of the Atmospheric Sciences

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Multiscale convective wave disturbances with structures broadly resembling observed tropical waves are found to emerge spontaneously in a nonrotating, two-dimensional cloud model forced by uniform cooling. To articulate the dynamics of these waves, model outputs are objectively analyzed in a discrete truncated space consisting of three cloud types (shallow convective, deep convective, and stratiform) and three dynamical vertical wavelength bands. Model experiments confirm that diabatic processes in deep convective and stratiform regions are essential to the formation of multiscale convective wave patterns. Specifically, upper-level heating (together with low-level cooling) serves to preferentially excite discrete horizontally propagating wave packets with roughly a full-wavelength structure in troposphere and "dry" phase speeds c n in the range 16-18 m s Ϫ1. These wave packets enhance the triggering of new deep convective cloud systems, via low-level destabilization. The new convection in turn causes additional heating over cooling, through delayed development of high-based deep convective cells with persistent stratiform anvils. This delayed forcing leads to an intensification and then widening of the low-level cold phases of wave packets as they move through convecting regions. Additional widening occurs when slower-moving (ϳ8 m s Ϫ1 ) "gust front" wave packets excited by cooling just above the boundary layer trigger additional deep convection in the vicinity of earlier convection. Shallow convection, meanwhile, provides positive forcing that reduces convective wave speeds and destroys relatively small-amplitude-sized waves. Experiments with prescribed modal wind damping establish the critical role of short vertical wavelengths in setting the equivalent depth of the waves. However, damping of deep vertical wavelengths prevents the clustering of mesoscale convective wave disturbances into larger-scale envelopes, so these circulations are important as well.

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Upscale effects in simulations of tropical convection on an equatorial beta-plane

Cited by 12 publications

References 26 publications

Context and Aims of the Aqua-Planet Experiment

Context and Aims of the Aqua-Planet Experiment

The Effects of Explicit versus Parameterized Convection on the MJO in a Large-Domain High-Resolution Tropical Case Study. Part I: Characterization of Large-Scale Organization and Propagation*

Multiscale Convective Wave Disturbances in the Tropics: Insights from a Two-Dimensional Cloud-Resolving Model

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