The Impact of Microphysics, Resolution, and Domain Size on Tropical Convection Systems

Continuing advances in computing power are allowing atmospheric prediction models to be run at progressively finer scales of resolution, using increasingly more sophisticated physical parameterizations and numerical methods. The representation of cloud microphysical processes is a key component of these models. During the past decade, both research and operational numerical weather prediction (NWP) models have started using more complex microphysical schemes originally developed for high-resolution cloud-resolving models (CRMs). Recently, a four-class ice (cloud ice, snow, graupel and hail) Goddard microphysics scheme was developed for the Goddard Cumulus Ensemble (GCE), NASA Unified WRF (NU-WRF) and Goddard Multi-scale Modeling Framework (GMMF) models; all of the models show promising results for several case studies (e.g. MC3E, TWP-ICE and DYNAMO) compared to ground-based, and satellite observations (e.g., CloudSat, TRMM). In this talk, we will present results from numerical experiments using the GCE, NU-WRF and GMMF. Specifically, we examine the impact of horizontal resolution (and domain size) and microphysical schemes on simulated clouds and precipitation systems that occurred during DYNAMO and TWP-ICE. We will also show the impact of the resolution (1000 m, 500 m and 250 m), domain size (2048, 1014, 512 km) and dimension (2D vs 3D) on the transition from shallow clouds to deep convection and stratiform rain. Finally, the impact of various microphysics schemes (the Goddard 3-ICE, Goddard 4-ICE, spectral bin and Morrison schemes) on simulated cloud properties are examined, including cloud (upward and downward) velocity, radar reflectivity (CFADs), latent heating profiles, and diurnal variation.