Tuesday 10 Dec 2019Direct estimation of entrainment, detrainment and other cloud properties

Prof. Peter Clark - University of Reading

Harrison 103 13:30-15:30

The sub-project 'Circle-A' of the ongoing 'ParaCon' project is taking a 'turbulence-based' approach to addressing the problem of representing convective clouds in the 'grey zone'. However, this means more than just finding an appropriate 'eddy diffusivity'. While it has long been recognised that, in the case of the atmospheric boundary layer, 'turbulence' includes large, coherent, structures, the link to traditional mass-flux convection schemes is a relatively recent idea, primarily expressed through 'Eddy-Diffusivity Mass-flux' (EDMF) schemes. Such schemes retain the simplistic model of coherent structures as 'plumes' or 'thermal', and rely on parametrization of 'entrainment' and 'detrainment'. However, it is becoming more evident that we have a number of different ideas concerning what we mean by these terms, and how to evaluate them. After a brief introduction to Circle-A, I shall describe a Lagrangian-tracer-based approach to deriving these, and other, quantities and, hopefully, put them in context with other approaches.

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