Derivation and validation of estimation model of rainfall kinetic energy under the canopy

Abstract. Canopy interception alters the kinetic energy of raindrops reaching the ground, which has important implications for soil erosion, water conservation, and ecosystem functioning. A novel estimation model for the kinetic energy of rainfall under the canopy is developed by stratifying the canopy using parameters such as leaf area index and leaf inclination angle, explicitly distinguishing between canopy-dripped and splashed raindrops. The efficacy of the model is subsequently assessed and analyzed through a comprehensive examination of nine field datasets encompassing LiDAR and raindrop spectrum observations. The simulated under-canopy total kinetic energy, splashing drop kinetic energy, and dripping drop kinetic energy showed total R2 values of 0.769, 0.572 and 0.773, total RMSE values of 18.7, 2.0 and 18.7 Jm-2h-1, with measurement including uncertainty of 54.1 ± 12.4, 3.7 ± 0.1 and 50.4 ± 12.4 Jm-2h-1, respectively. Simulations indicate that the under-canopy raindrop spectrum and kinetic energy are primarily controlled by canopy structure and vary less than above-canopy rainfall properties across the observed events. Sensitivity analysis shows that the model is generally robust, with rainfall intensity, the pinning proportion coefficient, LAI and surface contact angle exerting the greatest influence, while other factors have limited impact. Remaining limitations, including simplified branch-drip representation, component-partitioning assumptions and measurement uncertainties, highlight the need for improved parameterization and broader observations.