Incorporating Salinity Effects to Improve the Simulation of Water-Heat Fluxes in Coastal Wetlands Using the Noah-MP Model

Soil salinity plays a critical role in regulating wetland evapotranspiration (ET)—including both soil evaporation and plant transpiration—by directly affecting water movement and indirectly altering plant physiology and ecosystem structure. However, common land surface models (LSMs) overlook salinity effects on ET, contributing to uncertainties in simulating land–atmosphere interactions and climate processes, particularly in the coastal regions. In this study, the Noah-MP LSM was enhanced to incorporate the effects of soil salinity. Using half-hourly meteorological forcing data and observed soil properties and salinity from the Dongtan coastal wetland in Shanghai (July–December 2023), we evaluated model performance before and after this improvement. Comparisons with in situ observations show that incorporating salinity significantly reduces the model's overestimation of latent heat flux—by up to 90 W/m² during the cold season—and decreases cumulative ET bias by as much as 130 mm, with the error rate reduced by approximately 33%. This improvement is largely attributed to salinity constraints on soil evaporation under sparse vegetation conditions. These findings highlight salinity as a key regulatory factor in wetland hydrothermal dynamics and offer a promising approach to improving LSM accuracy in coastal wetland environments.