A Physically-based, Subgrid Parametrization for the Production and Maintenance of Mixed-phase Clouds in a General Circulation Model

• Published in: Journal of the Atmospheric Sciences
• Main Authors: Furtado, K, Field, PR, Boutle, IA, Morcrette, CJ, Wilkinson, JM
• Format: Article in Journal/Newspaper
• Language: English
• Published: American Meteorological Society 2016
• Subjects: Arctic; Southern Ocean
• Online Access: https://eprints.whiterose.ac.uk/91977/; https://eprints.whiterose.ac.uk/91977/8/jas-d-15-0021%252E1.pdf; https://doi.org/10.1175/JAS-D-15-0021.1

A physically based method for parametrizing the role of subgrid scale turbulence in the production and maintenance of supercooled liquid water and mixed-phase clouds is presented. The approach used is to simplify the dynamics of supersaturation fluctuations to a stochastic differential equation that can be solved analytically, giving increments to the prognostic liquid cloud fraction and liquid water content fields in a General Circulation Model (GCM). Elsewhere, it has been demonstrated that the approach captures the properties of decameter-resolution Large Eddy Simulations of a turbulent mixed-phase environment. In this paper it is shown that it can be implemented in a GCM and the effects that this has on Southern Ocean biases and on Arctic stratus are investigated.