Influence of Tidal Inundation and Salinity on the Generalized Complementary Relationship for Evaporation in a Mangrove Ecosystem

Abstract Mangrove ecosystems, located at the interface between land and sea, are characterized by periodic tidal inundation and salinity fluctuations, which exhibit complex land–atmosphere interactions influencing the water cycle. This study evaluated the Sigmoid Generalized Complementary (SGC) equation for estimating evaporation in a subtropical mangrove forest in the southern China, focusing on the effects of tidal inundation time fraction (TI) and salinity (SAL) on both evaporation and model parameters. Using a decade of eddy covariance and meteorological data, we found that the SGC equation accurately captured the diurnal and seasonal evaporation dynamics achieving high performance ( R 2 = 0.94, RMSE = 11.98 W m −2 ; daily) with the best‐fit parameters ( α = 1.13, b = ∞). α is the atmospheric character parameter representing the atmospheric advection effect and b is the land surface parameter representing the surface moisture condition. Although TI had limited impact on the evaporation magnitude, it sufficiently affected parameter b which transitioned from land‐like to open‐water characteristics as inundation increased. Salinity did not significantly affect the SGC parameters but was negatively correlated with monthly evaporation, especially when exceeding about 15 PSU. Diurnally, evaporation was primarily controlled by net radiation rather than water level or salinity, and no water‐energy decoupling was observed at the seasonal scale. These findings demonstrate the robustness and applicability of the SGC framework in intertidal environments, offer a new perspective for modeling evaporation in intertidal zones, and provide new insights into the interactions between hydrological drivers, salinity stress, and evaporation in mangroves.