Long-term variations in diurnal precipitation pattern and their attribution to aerosols across China

Precipitation and its diurnal cycle are closely connected with the thermodynamic and dynamic processes of the Earth system, significantly influencing the climate. This study evaluates the performance of reanalysis and CMIP6 datasets in reproducing hourly precipitation events during warm seasons across China from 1980 to 2014. Statistical results indicate that while these datasets better reproduce the distribution of mean intensity than mean duration, neither fully captures the trends in mean duration or intensity. The reanalysis and CMIP6 datasets can reproduce the late afternoon precipitation peak, but it is difficult to capture the early morning peak of long-duration events except for ERA5 and HadGEM3-GC31-MM. Short-duration events show advanced peak time trends over most stations, while long-duration events exhibit delayed trends, a pattern not comprehensively replicated by other datasets. Additionally, the impact of aerosols on precipitation peak times varies across three regions: North China Plain (NCP), Yangtze River Delta (YRD) and the Pearl River Delta (PRD). In the NCP, early morning and midnight peaks advance for precipitation that lasts 4–6 h, potentially linked to aerosol radiative effects. In contrast, in the YRD and PRD, both early morning and late afternoon peaks are delayed 1–2 h, associated with the radiative and microphysical effects of aerosols. This study also highlights that aerosol impacts on precipitation peak times are dependent on meteorological conditions. In the NCP, the radiative effect of absorbing aerosols is enhanced under low-CAPE conditions. In the YRD, the aerosol invigoration effect is inhibited under high-WS conditions, whereas in the PRD, a low-WS environment enhances the microphysical effect of aerosols.