The role of shallow convection in ECMWF's Integrated Forecasting System

TitleThe role of shallow convection in ECMWF's Integrated Forecasting System
Publication TypeMiscellaneous
Year of Publication2014
AuthorsBechtold, P, Sandu, I, Klocke, D, Semane, N, Ahlgrimm, M, Beljaars, ACM, Forbes, R, Rodwell, M
Secondary TitleTechnical Memorandum
Number725
Abstract

In the context of the European Union EUCLIPSE project the role of shallow convection was assessed in the European Centre forMedium-RangeWeather Forecasts (ECMWF) Integrated Forecasting System (IFS). Three model configurations differing in the treatment of shallow convection were used to explore the impact on process tendencies, weather forecasts and climate simulations. In the summary of this work presented here, special emphasis is put on the interaction of processes and the altered balance between processes when a physical parameterization is removed, or replaced by a conceptually different approach to the treatment of shallow convection. The activities related to boundary layer clouds that took place at ECMWF in the past few years also revealed that at present there are several inconsistencies between the parameterizations contributing to the representation of cloudy boundary layers. These inconsistencies are listed here, and a strategy towards a more consistent description of moist boundary layers is introduced. Finally, a first attempt to harmonize the computation of convective cloud base and subcloud properties across the shallow convection scheme and the turbulent diffusion scheme is described.