Transport-constrained eddy–mean energetics sustain extreme rainfall over China

Abstract Extreme summer rainfall over China has intensified in recent decades, yet the processes that organize moisture transport and sustain extreme ascent remain unclear. Here we show that these roles are dynamically distinct. Using a pressure-coordinate moisture budget, we find that vertical moisture advection dominates column moisture transport in both normal and extreme rainfall, but its control shifts from background ascent to transient-eddy-driven uplift during extremes. This reorganization intensifies precipitation without changing the vertical direction of moisture transport. Energetically, enhanced ascent is not supported by increased net radiative input into the atmospheric column. Instead, atmospheric column energy balance analysis shows that extreme ascent is sustained by enhanced horizontal moist-enthalpy import, dominated by transient-eddy dry-enthalpy advection. Cloud radiative anomalies primarily redistribute energy vertically rather than increase net column heating. Extreme Chinese rainfall therefore operates within a transport-constrained energetic regime, in which lateral energy supply sustains ascent and dynamical reorganization concentrates moisture.