Development and multi-decadal evaluation of the CWRF–CoLM regional land–atmosphere coupled system over China 

Regional climate simulations over China are strongly influenced by land–atmosphere interactions. Yet many widely used regional modeling systems still rely on land-surface schemes that oversimplify subgrid heterogeneity and require homogeneous grid setups between land and atmosphere. To address these limitations, we develop a new regional coupled system, CWRF-CoLM, which interactively links the Climate-Weather Research and Forecasting model (CWRF; a climate extension of WRF) with the Common Land Model (CoLM).Built on the CPL7 flux coupler, the coupling design has two key features. First, it preserves CoLM’s native data structures so that subgrid land processes are represented explicitly rather than collapsed into an “effective” surface grid. Second, it enables cross-resolution configurations in which the atmospheric and land components run on different horizontal grids, while maintaining consistent exchanges of state variables and surface fluxes via coupler-based mapping.We perform a multi-decadal regional climate integration over China for 1990-2022 and evaluate CWRF-CoLM against a baseline configuration using the original CWRF land-surface setup. The long-term simulations show that CWRF-CoLM substantially improves climatological performance, including reduced systematic biases in near-surface climate and more realistic surface heat fluxes and their partitioning (Bowen ratio). Overall, the CPL7-based coupling strategy, together with explicit retention of land subgrid structure, enhances the fidelity of long-term regional climate simulations and provides a robust platform for land-atmosphere process studies and regional climate downscaling.