Thermodynamic and Dynamic Effects of Parametric Uncertainties on the Simulated Interannual‐To‐Interdecadal Variability of Summertime Precipitation Over China

Abstract Climate models are essential tools for understanding and predicting precipitation variability, yet the parameterization of sub‐grid cloud and convection processes remain a major uncertainty source of precipitation simulations. This study presents a comprehensive analysis of the uncertainties in the simulated precipitation variability over dry and wet regions of China based on a 40‐year parameter‐perturbed ensemble spanning 1975 to 2014. The dynamic and thermodynamic contributions of physical parameters to precipitation variability are quantified. The results demonstrate that precipitation variability is mainly attributed to the change in the thermodynamic component of precipitation in China. However, the uncertain range of the dynamic component is comparable with that of the thermodynamic component, particularly at interannual timescale. Parametric sensitivity analyses suggest that at interdecadal timescale, most of the uncertainty in precipitation variability arises from internal model stochasticity. At interannual timescale, nearly 50% of the uncertainty is contributed by the parameter related to convective precipitation evaporation. Stronger convective precipitation evaporation rate simultaneously increases the dynamic and thermodynamic components of precipitation, suggesting the responses in the two components are tightly interconnected. The increased evaporation rate suppresses local convective precipitation but, via increasing low‐level water vapor and promoting remote moisture transport, strongly enhances large‐scale precipitation, leading to a net increase in total precipitation in convergence zones over tropical and subtropical monsoon regions and then enhancing upward motion in turn. Compared to drier years, stronger convergence in wetter years is more favorable for the long‐range transport of moisture to mid‐high latitudes, thereby enhancing precipitation interannual variability in China.