A Catchment‐Based Hierarchical Spatial Tessellation Approach to a Better Representation of Land Heterogeneity for Hyper‐Resolution Land Surface Modeling

Abstract

AbstractTo represent the physical processes at hillslope scales for hyper‐resolution land surface modeling, we propose a hierarchical, catchment‐based spatial tessellation method. The land surface is divided into a hierarchical structure: catchments, height bands along hillslopes within a catchment, and land cover patches within a height band. This catchment‐based structure explicitly represents hillslope drainage networks and can be applied at various resolutions determined by a pre‐defined maximum height band size. The proposed tessellation method is superior to the conventional grid‐based structure in representing land surface heterogeneity, resulting in a higher aggregation skill through the height band representation. The spatial variations in air temperature, leaf area index, saturated soil hydraulic conductivity, and soil porosity are generally lower within a height band than those in a conventional rectangular grid, reflecting the nature of topographic control on climate, vegetation, and soil distribution. The improvement in aggregation skill depends on resolutions and terrain slope angle, more pronounced at 1/6° model resolution and over steeper terrains. Finally, we demonstrate that our proposed catchment‐based structure performs better than the grid‐based structure through modeling tests over the Columbia River basin at resolutions of 1/2°, 1/6°, and 1/20° and a global test at 1/2° using the ILAMB model evaluation metrics.