This study compares the error characteristics associated with two-grid refinement approaches including global variable resolution and nesting for high resolution regional climate modeling. The global variable resolution model, Model for Prediction Across Scales-Atmosphere (MPAS-A), and the limited area model, Weather Research and Forecasting (WRF) model, are compared in an idealized aqua-planet context. For MPAS-A, simulations have been performed with a quasi-uniform resolution global domain at coarse (1o) and high (0.25o) resolution, and a variable resolution domain with a high resolution region at 0.25o configured inside a coarse resolution global domain at 1o resolution. Similarly, WRF has been configured to run on a coarse (1o) and high (0.25o) tropical channel domain as well as a nested domain with a high resolution region at 0.25o nested two-way inside the coarse resolution (1o) tropical channel. The variable resolution or nested simulations are compared against the high resolution simulations.
Both models respond to increased resolution with enhanced precipitation and significant reduction in the ratio of convective to non-convective precipitation. The limited area grid refinement induces zonal asymmetry in precipitation (heating), accompanied by zonal anomalous Walker-like circulations and standing Rossby wave signals. Within the high resolution limited area, the zonal distribution of precipitation is affected by advection in MPAS-A and by the nesting strategy in WRF. In both models, the propagation characteristics of equatorial waves are not significantly affected by the variations in resolution.