Abstract
The Australian Community Climate and Earth-System Simulator (ACCESS) is used to test the sensitivity of heavy precipitation to various model configurations: horizontal resolution, domain size, rain rate assimilation, perturbed physics, and initial condition uncertainties, through a series of convection-permitting simulations of three heavy precipitation (greater than 200 mm day−1) cases in different synoptic backgrounds. The larger disparity of intensity histograms and rainfall fluctuation caused by different model configurations from their mean and/or control run indicates that heavier precipitation forecasts have larger uncertainty. A cross-verification exercise is used to quantify the impacts of different model parameters on heavy precipitation. The dispersion of skill scores with control run used as “truth” shows thatthe impacts of the model resolution and domain size on the quantitative precipitation forecast are not less than those of perturbed physics and initial field uncertainties in these not intentionally selected heavy precipitation cases. The result indicates that model resolution and domain size should be considered as part of probabilistic precipitation forecasts and ensemble prediction system design besides the model initial field uncertainty.
Highlights
Many studies show the importance of higher resolution in improving the forecast skill
The emphasis on horizontal resolution in most mesoscale simulation is based on the implicit assumption that errors from artificial lateral boundaries and the effects of limited domain size may not play a significant role in the dynamics of the mesoscale system
The model forecast of rainfall accumulation is interpolated to the radar rainfall analysis grid (1.5 km spacing Cartesian grid with radar at the origin) with bilinear interpolation approach and the model forecasted rainfall is set to missing for those grid points where the observed precipitation is not available [23]
Summary
Many studies show the importance of higher resolution in improving the forecast skill. The results from short-range weather forecasting [5,6,7] indicate that such convection-permitting models outperform those coarser resolution models that require a convective parameterization. The limited domains models need artificial lateral boundaries, which introduce additional uncertainties and errors into the weather forecast. The emphasis on horizontal resolution in most mesoscale simulation is based on the implicit assumption that errors from artificial lateral boundaries and the effects of limited domain size may not play a significant role in the dynamics of the mesoscale system. Studies have shown that both of the domain size and horizontal resolution of limited area model influence the spectrum of resolved scale and the nature of scale interaction in the model dynamics [8, 9]. Laprise et al [11] discussed many limitations and sources of error associated with limited area models, such as the resolution
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