The Impacts of Global Convection-Permitting Resolution across Scales: From Tropical Convection to Global Subseasonal Teleconnections

This talk presents results from four 28-day global simulations using the Model for Prediction Across Scales (MPAS) at 3-km horizontal grid spacing. These runs are motivated by the previously studied benefits of convection-permitting resolution for simulated tropical convection, the MJO, and forecast biases. Here, we extend these results to address the following question: by better simulating the characteristics of tropical deep convection, can a global convection-permitting model reliably improve extended large-scale extratropical circulation predictions via convection-induced teleconnections?

In order to explore this question, the 3-km global MPAS simulations are compared to 15-km runs with and without convective parameterization, as well as a “tropical channel” simulation with 3-km resolution in the tropics transitioning to 15-km grid spacing in the extratropics.

We present tropical precipitation statistics for all cases and configurations to address the impact of convection-permitting resolution and cumulus parameterization on the frequency and intensity of convection. The structure and propagation of the Madden-Julian Oscillation (MJO) are compared among the MPAS simulations, highlighting a tendency for the 3-km configuration to more faithfully produce large-scale organized convection. Extratropical circulation, at different temporal and spatial scales, is also evaluated to determine the impact, if any, of improved tropical convection on global subseasonal forecast skill.