PNNL

Abstract

Accurately representing the precipitation diurnal cycle has long been a challenge for global climate models. Here we evaluate and compare 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 the realistic precipitation diurnal cycle.