Parcel Model (parcel + model)

Distribution by Scientific Domains


Selected Abstracts


Physically based two-moment bulkwater parametrization for warm-cloud microphysics

THE QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY, Issue 596 2004
Jen-Ping Chen
Abstract A two-moment bulkwater parametrization scheme for warm-cloud microphysics is developed via statistical analyses of results from a detailed parcel model. This computationally efficient scheme is quite accurate and produces bulkwater properties which resemble the results from a fully explicit microphysical model. It responds sensitively to the effect of aerosol types on the cloud drop number concentration and the timing of rain initiation. Diagnostic formulae are also provided for the group fall velocity, number and mass sedimentation fluxes, the radar reflectivity factor, and the effective radii of cloud drops and raindrops. This physically sound and easy to use parametrization scheme could be useful in improving the microphysical representation in regional- and cloud-scale models. Copyright © 2004 Royal Meteorological Society [source]


Microphysical structure of a developing convective snow cloud simulated by an improved version of the multi-dimensional bin model

ATMOSPHERIC SCIENCE LETTERS, Issue 3 2010
Ryohei Misumi
Abstract A new version of the multi-dimensional bin-microphysics model, which employs four dimensions to represent ice-particle properties (ice mass, solute mass, aspect ratio and volume), was developed. The model was incorporated into an adiabatic parcel model to simulate the developing stage of a convective snow cloud observed over the Sea of Japan. The results suggest that crystals originating from deposition/condensation,freezing nuclei grow the fastest in the cloud, and isometric crystals among them effectively act as embryos of graupels. Copyright © 2010 Royal Meteorological Society [source]


Investigating the simulation of cloud microphysical processes in numerical models using a one-dimensional dynamical framework

ATMOSPHERIC SCIENCE LETTERS, Issue 3 2009
Christopher Dearden
Abstract This paper describes the method by which the performance of a suite of microphysics schemes of varying levels of complexity can be compared within an idealised framework. The purpose is to establish the level of microphysical sophistication required for the successful simulation of liquid clouds in operational models, paying particular attention to the required level of coupling with aerosols. Initial results from a lagrangian parcel model are able to demonstrate the importance of the treatment of droplet activation in dual moment schemes for predicting droplet number qualitatively. Subsequent testing within a one-dimensional (1D) column model using the existing factorial method (FM) will aim to quantify the importance of microphysical complexity on precipitation and cloud albedo relative to the effects of meteorology. Copyright © 2009 Royal Meteorological Society [source]


Aerosol growth and activation in polluted air masses over a tropical metropolis in the Indian sub-continent

ATMOSPHERIC SCIENCE LETTERS, Issue 2 2009
S. Varun Raj
Abstract Air pollution can affect cloud formation in more than one way. When the pollutant gases are condensable (e.g. oxides of sulphur), then the process of aerosol activation is eased to a certain extent aiding cloud formation. However, polluted days are often characterised by low updraught speeds which inhibit aerosol growth. In this study, we have critically examined the aerosol activation process in a polluted coastal environment where both effects are present. We have concentrated on the Chennai region (one of the largest cities in the world) of the Indian sub-continent because its pace of industrialisation is increasing rapidly, adding to increasing SO2 pollution over the years. Air masses over Chennai contain a mixture of aerosol particles including NaCl, because of its proximity to the Bay of Bengal, along with ammonium sulphate. We have used observational data along with a detailed microphysical chemical parcel model to study cloud activation effects. We find that over Chennai, often the presence of the condensable pollutant vapour (SO2) more than compensates for the low updraught speeds by lowering the level of maximum super saturation significantly. This latter effect favours the activation of ammonium sulphate as well as NaCl aerosol particles. We have undertaken a systematic analysis to quantify the relative strengths of these two competing effects and find that even with low updraught speeds, oxides of sulphur can perturb the activation domain comprising a mixture of aerosol particles to such an extent that aerosol particles in polluted environments often grow efficiently. This effect is non-intuitive in the sense that one associates smaller cloud droplet sizes with polluted air masses. This is the first microphysical modelling study for the Indian sub-continent where National Environmental Engineering Research Institute (NEERI) observations have been applied to cloud microphysical processes. Copyright © 2009 Royal Meteorological Society [source]