Improvement of the PDI Model for Regional Hydrological Modeling and Land Surface Process Simulation

We integrated the bimodal-PDI scheme into the Community Land Model (CLM5) for Tibetan wetland sites. Benchmark simulations using in-situ soil moisture networks and eddy covariance towers showed that the PDI-based parameterization reduced surface soil water biases by 0.04 cm³•cm⁻³ and improved latent heat flux predictions by 15-22%. Model-data assimilation revealed that uncertainty in key parameters (α, n) decreased by 40% compared to unimodal van Genuchten schemes. Long-term simulations (2010-2020) indicated that runoff estimates for wetland catchments were improved by 12-18% (NSE increase from 0.68 to 0.80). This work provides a quantitative basis for incorporating hydric soil hydraulic complexity into land surface and regional climate models.