Sensitivity to Horizontal Resolution in the AGCM Simulations of Warm Season Diurnal Cycle of Precipitation over the United States and Northern Mexico

Abstract

This study examines the sensitivity of the North American warm season diurnal cycle of precipitation to changes in horizontal resolution in three atmospheric general circulation models, with a primary focus on how the parameterized moist processes respond to improved resolution of topography and associated local/regional circulations on the diurnal time scale. It is found that increasing resolution (from approximately 2°to 1 ⁄2°in latitude-longitude) has a mixed impact on the simulated diurnal cycle of precipitation. Higher resolution generally improves the initiation and downslope propagation of moist convection over the Rockies and the adjacent Great Plains. The propagating signals, however, do not extend beyond the slope region, thereby likely contributing to a dry bias in the Great Plains. Similar improvements in the propagating signals are also found in the diurnal cycle over the North American monsoon region as the models begin to resolve the Gulf of California and the surrounding steep terrain. In general, the phase of the diurnal cycle of precipitation improves with increasing resolution, though not always monotonically. Nevertheless, large errors in both the phase and amplitude of the diurnal cycle in precipitation remain even at the highest resolution considered here. These errors tend to be associated with unrealistically strong coupling of the convection to the surface heating and suggest that improved simulations of the diurnal cycle of precipitation require further improvements in the parameterizations of moist convection processes.

The role of meteorological processes in the description of uncertainty for climate change decision-making

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Simulation of Diurnal Rainfall Variability over the Maritime Continent with a High-Resolution Regional Climate Model

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“…Reducing the grid spacing has been shown to improve the model's ability to simulate the diurnal cycle of precipitation (Lee et al 2007;Rauscher et al 2010;Walther et al 2013;Kendon et al 2012;Dirmeyer et al 2012). This is often attributed to the enhanced representation of complex terrain and land surface processes (Kendon et al 2012).…”