Simulation of Tropical Convective Systems. Part I: A Cumulus Parameterization

Frank, William M.; Cohen, Charles L.

doi:10.1175/1520-0469(1987)044<3787:sotcsp>2.0.co;2

Cited by 85 publications

(55 citation statements)

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“…(26) requires knowledge of the vertical velocity within each parcel, w cp , which is also necessary for driving the droplet activation and ice nucleation parameterizations. This is calculated by solving (Frank and Cohen, 1987) 1 2…”

Section: Microphysics Of Convective Cumulusmentioning

confidence: 99%

Development of two-moment cloud microphysics for liquid and ice within the NASA Goddard Earth Observing System Model (GEOS-5)

et al. 2014

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Abstract. This work presents the development of a twomoment cloud microphysics scheme within version 5 of the NASA Goddard Earth Observing System (GEOS-5). The scheme includes the implementation of a comprehensive stratiform microphysics module, a new cloud coverage scheme that allows ice supersaturation, and a new microphysics module embedded within the moist convection parameterization of GEOS-5. Comprehensive physically based descriptions of ice nucleation, including homogeneous and heterogeneous freezing, and liquid droplet activation are implemented to describe the formation of cloud particles in stratiform clouds and convective cumulus. The effect of preexisting ice crystals on the formation of cirrus clouds is also accounted for. A new parameterization of the subgrid-scale vertical velocity distribution accounting for turbulence and gravity wave motion is also implemented. The new microphysics significantly improves the representation of liquid water and ice in GEOS-5. Evaluation of the model against satellite retrievals and in situ observations shows agreement of the simulated droplet and ice crystal effective radius, the ice mass mixing ratio and number concentration, and the relative humidity with respect to ice. When using the new microphysics, the fraction of condensate that remains as liquid follows a sigmoidal dependency with temperature, which is in agreement with observations and which fundamentally differs from the linear increase assumed in most models. The performance of the new microphysics in reproducing the observed total cloud fraction, longwave and shortwave cloud forcing, and total precipitation is similar to the operational version of GEOS-5 and in agreement with satellite retrievals. The new microphysics tends to underestimate the coverage of persistent low-level stratocumulus. Sensitivity studies showed that the simulated cloud properties are robust to moderate variation in cloud microphysical parameters. Significant sensitivity remains to variation in the dispersion of the ice crystal size distribution and the critical size for ice autoconversion. Despite these issues, the implementation of the new microphysics leads to a considerably improved and more realistic representation of cloud processes in GEOS-5, and allows the linkage of cloud properties to aerosol emissions.

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Section: Microphysics Of Convective Cumulusmentioning

confidence: 99%

Development of two-moment cloud microphysics for liquid and ice within the NASA Goddard Earth Observing System Model (GEOS-5)

et al. 2014

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“…The ensemble members are chosen to allow a large spread in terms of accumulated convective rainfall (Bao et al, 2011). The ensemble of closures consists of disturbances around the classical closures of Grell (1993); a simplified version of Arakawa and Schubert (1974) and Kain and Fritsch (1993), low-level omega (Brown, 1979;Frank and Cohen, 1987) and integrated vertical advection of moisture (Krishnamurti et al, 1983), which is a Kuo (1974) type closure, hereafter GR, AS, KF, LO and MC, respectively. GD used these members to determine the ensemble mean.…”

Section: A F Dos Santos Et Al: Using the Firefly Optimization Methodsmentioning

confidence: 99%

Using the Firefly optimization method to weight an ensemble of rainfall forecasts from the Brazilian developments on the Regional Atmospheric Modeling System (BRAMS)

et al. 2013

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Abstract. In this paper we consider an optimization problem applying the metaheuristic Firefly algorithm (FY) to weight an ensemble of rainfall forecasts from daily precipitation simulations with the Brazilian developments on the Regional Atmospheric Modeling System (BRAMS) over South America during January 2006. The method is addressed as a parameter estimation problem to weight the ensemble of precipitation forecasts carried out using different options of the convective parameterization scheme. Ensemble simulations were performed using different choices of closures, representing different formulations of dynamic control (the modulation of convection by the environment) in a deep convection scheme. The optimization problem is solved as an inverse problem of parameter estimation. The application and validation of the methodology is carried out using daily precipitation fields, defined over South America and obtained by merging remote sensing estimations with rain gauge observations. The quadratic difference between the model and observed data was used as the objective function to determine the best combination of the ensemble members to reproduce the observations. To reduce the model rainfall biases, the set of weights determined by the algorithm is used to weight members of an ensemble of model simulations in order to compute a new precipitation field that represents the observed precipitation as closely as possible. The validation of the methodology is carried out using classical statistical scores. The algorithm has produced the best combination of the weights, resulting in a new precipitation field closest to the observations.

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“…(78) of Arakawa and Schubert (1974) an element are alike" Chappell, 1980, p. 1724). This argument (see also Frank and Cohen, 1987;Fritsch and Kain, 1993) fails to recognize that although there may be only a small number of clouds present in a relatively small grid box, the properties of those clouds may not be knowable a priori but rather are randomly drawn from those of the statistical ensemble. As shown by Plant and Craig (2008) then, the consideration of smaller grid boxes actually leads not to a formulation based on a single-plume with prescribed properties but rather to stochastic parameterizations in which a spectral formulation is sub-sampled.…”

Section: R S Plant: the Basis For Bulk Mass Flux Parameterizationmentioning

confidence: 99%

A review of the theoretical basis for bulk mass flux convective parameterization

Plant

2010

Atmos. Chem. Phys.

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Abstract. Most parameterizations for precipitating convection in use today are bulk schemes, in which an ensemble of cumulus elements with different properties is modelled as a single, representative entraining-detraining plume. We review the underpinning mathematical model for such parameterizations, in particular by comparing it with spectral models in which elements are not combined into the representative plume. The chief merit of a bulk model is that the representative plume can be described by an equation set with the same structure as that which describes each element in a spectral model. The equivalence relies on an ansatz for detrained condensate introduced by Yanai et al. (1973) and on a simplified microphysics. There are also conceptual differences in the closure of bulk and spectral parameterizations. In particular, we show that the convective quasi-equilibrium closure of Arakawa and Schubert (1974) for spectral parameterizations cannot be carried over to a bulk parameterization in a straightforward way. Quasi-equilibrium of the cloud work function assumes a timescale separation between a slow forcing process and a rapid convective response. But, for the natural bulk analogue to the cloud-work function, the relevant forcing is characterised by a different timescale, and so its quasi-equilibrium entails a different physical constraint. Closures of bulk parameterizations that use a parcel value of CAPE do not suffer from this timescale issue. However, the Yanai et al. (1973) ansatz must be invoked as a necessary ingredient of those closures.

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Simulation of Tropical Convective Systems. Part I: A Cumulus Parameterization

Cited by 85 publications

References 0 publications

Development of two-moment cloud microphysics for liquid and ice within the NASA Goddard Earth Observing System Model (GEOS-5)

Development of two-moment cloud microphysics for liquid and ice within the NASA Goddard Earth Observing System Model (GEOS-5)

Using the Firefly optimization method to weight an ensemble of rainfall forecasts from the Brazilian developments on the Regional Atmospheric Modeling System (BRAMS)

A review of the theoretical basis for bulk mass flux convective parameterization

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