. Implementation of the ECMWF IFS cumulus convection scheme in the NOAA GFS model and its impact on convectively coupled equatorial waves.

Abstract
There is a longstanding challenge in numerical weather and climate prediction to accurately model the dynamics of the tropical atmosphere. This is at large due to the complex nature of the interaction between cumulus convection and tropical wave dynamics, since the processes involved are only partly resolved, and many remain fully parameterized. In recent years, progress on modeling convectively coupled equatorial waves in the tropics has been made, owing to higher resolution model simulations, improvements in coupling between atmosphere and ocean, and the introduction of more sophisticated parameterization schemes of sub-grid scale processes. For seasonal prediction, the European Centre for Medium range Weather Forecasts (ECMWF) stands out in modeling tropical variability, and in a recent comparison with the NOAA Global Forecast System (GFS), the ECMWF model was demonstrated much better at representing the Matsuno dispersion curves of convectively coupled equatorial wave modes. In this study we introduce the cumulus convection parameterization from the ECMWF model in a research version of the GFS, and study the interaction between the convection scheme and other physical processes in the GFS. We show that a consistent treatment of the interaction between convective plumes in the Planetary Boundary Layer (PBL) and the convection scheme is necessary in order to replicate the tendency profiles out of the ECMWF model. We further show that the GFS with the ECMWF convection scheme has more organized convection, and tends to propagate waves to a larger extent than the control as a consequence of stronger coherence between low level convergence and precipitation.