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Abstract

Accurately representing the precipitation diurnal cycle has long been a challenge for global climate models (GCMs). Here we evaluate the precipitation diurnal cycle in the DYAMOND global convection-permitting models (CPMs) and CMIP6 HighResMIP models. Comparison of the high- (25-50 km) and low-resolution (100-250 km) models with parameterized convection in HighResMIP shows that simply increasing model resolution does not noticeably improve the precipitation diurnal cycle. In contrast, CPMs can better capture the observed amplitude and timing of precipitation diurnal cycle. However, the simulated spatial variation of timing in CPMs is smaller than observed, leading to an exaggeration of the spatially averaged diurnal amplitude. The better-simulated precipitation diurnal cycle in the CPMs is tied to mesoscale convective systems (MCSs), which contribute about half of the total precipitation. The observed life cycle of MCSs, including initiation and mature stages, is well captured in the CPMs, leading to a more realistic precipitation diurnal cycle.

As a basic mode of climate variability, the diurnal cycle is a key metric that has been used to benchmark climate models. The current state-of-the-art GCMs struggle to accurately represent the precipitation diurnal cycle, frequently peaking too early compared to the observations. Due to the coarse resolution and the use of convection parameterization, GCMs are also unable to simulate organized convective storms, which often exhibit a distinct diurnal cycle. With the emergence of global storm-resolving models at kilometer-scale resolution, this study evaluates the diurnal cycle of precipitation simulated by global storm-resolving models and high-resolution GCMs. We find that at resolutions between similar to 25 and 250 km, increasing resolution has limited effects on the precipitation diurnal cycle but global CPMs can reproduce the observed precipitation diurnal cycle much better as they can better represent organized convective storms.

Precipitation diurnal cycle is systematically evaluated in DYAMOND simulations from global convection-permitting models (CPMs) and CMIP6 models Both the amplitude and phase of the precipitation diurnal cycle are better simulated by CPMs than CMIP6 high-resolution models The global CPMs excel in reproducing the precipitation diurnal cycle owing to better simulated mesoscale convective systems