Numerical Evaluation of JULES Surface Tiling Scheme with High-Resolution Atmospheric Forcing and Land Cover Data

Land surface heterogeneity exists at all spatial scales and has many important effects on energy, momentum and mass exchange between land and atmosphere. Land surface models (LSMs) partially consider surface subgrid heterogeneity (SSGH) effects through surface tiling methods. In this study, a series of numerical experiments were conducted to evaluate the performance of the Joint UK Land Environment Simulator (JULES) LSM's surface tiling scheme by combining atmospheric forcing data and land-cover fraction data at different horizontal resolutions. Our tests quantitatively show that the surface tiling scheme can have a significant impact on model simulated fields, but cannot reflect SSGH effects adequately. Soil is considered to be homogeneous across a single grid cell in the current surface tiling scheme, which results in soil-moisture dependent anomalies in simulated carbon flux. Our numerical results indicate that the current JULES LSM needs additional updates to consider subgrid scale heterogeneities of subsurface processes and soil-vegetation interactions.