Multi-fluid Modelling of Atmospheric Convection

Abstract:

I could not enter co-authors in the correct box. They are

Dr William McIntyre, University of Reading

Mr Daniel Shipley, University of Reading

Convection parameterizations have stubborn errors that hamper improvements in weather and climate models. Traditional parameterisations of convection assume that there is no net mass transport by convection so that all air that rises due to convection is balanced by compensating subsidence in the same column. Recent attempts to relax this assumption have not addressed the fundamental numercial problem of adding source terms to the continuity equation based on sub-grid-scale convection. These problems are addressed by formulating multi-fluid equations with a separate momentum, continuity, temperature and other transport equations for each fluid. The distinct fluids may be, for example, updrafts, downdrafts and the stable environment. This modelling framework requires an entirely new model rather than just a new parameterization for an existing dynamical core in order to simultaneously solve the flow in these interacting fluids.

We present the multi-fluid equations, a numerical method to solve them and results that reproduce aspects of well resolved dry convection but at very coarse resolution.