10.5    Subseasonal prediction in a global convection-permitting model: insights and challenges in simulating tropical convection and extratropical teleconnections.

Weber, Nick, and Cliff Mass, University of Washington

This talk presents results from four 28-day global simulations using MPAS at 3-km resolution. These runs are motivated by the previously studied benefits of convection-permitting resolution for simulated tropical convection, the MJO, and forecast biases, all of which have a substantial impact on global extended prediction.
In addition to the results of the 3-km global MPAS simulations, 15-km runs with and without convective parameterization will be described, as well as one “tropical channel” simulation with 3-km resolution in the tropics transitioning to 15-km grid spacing in the extratropics.
The talk presents 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 MJO are compared among the MPAS simulations, highlighting a tendency for the convection-permitting configuration to more faithfully produce large-scale organized convection. Convection-permitting simulations, on average, also tend to produce more accurate week-3 extratropical 500hPa height anomalies. In addition to these results, we discuss the relationship between tropical convection and moisture, the 3-dimensional structure of large-scale convection in the different simulation configurations, the connection between tropical convection and extratropical circulation patterns like the PNA, and potential future experiments.