A mass flux convection scheme with representation of cloud ensemble characteristics and stability-dependent closure

Abstract

The convection scheme used at the UK Meteorological Office in large-scale numerical models is described. The scheme uses a "bulk' cloud model to represent an ensemble of convective clouds and aims to represent shallow, deep and midlevel convection. A simple closure is employed, the initial convective mass flux being related to the stability of the initial convecting layer. The ability of the scheme to represent convective processes in a variety of situations is evaluated. The performance of the scheme in an 11-layer atmospheric general circulation model used in climate research at the UK Meteorological Office is also evaluated by comparing aspects of the simulated tropical flow from a recent 4-year integration with observed data. The scheme simulates the main areas of latent heat release and their variation throughout the year, although the Indian Monsoon is poorly simulated. -from Authors