Impacts of Topography-Based Downscaling of Atmospheric Forcing on Simulations of Land Surface Processes in Earth System Model
Topography has major control on land surface processes; however, the effects of its subgrid heterogeneity are not well represented in current Earth System Models (ESMs). Recently, a new topography-based subgrid structure has been implemented within the hierarchical subgrid spatial structure of the Energy Exascale Earth System Model (E3SM) Land Model (ELM) to improve the representation of land surface processes, with minimal increase in computational demand, while improving the ability to capture the spatial heterogeneity of atmospheric forcing and land cover influenced by topography. Also, methods of downscaling of atmospheric forcing from grid cell mean to subgrid topographic units have been implemented to capture the effects of subgrid topography on atmospheric processes. This study focuses on the evaluation of the impacts of the downscaling methods on simulations of land surface processes. More specifically, ELM simulations with subgrid topography driven by grid cell mean atmospheric forcing will be compared against ELM simulations driven by atmospheric forcing downscaled following topographic variability. Furthermore, to evaluate the impacts of the spatial downscaling of atmospheric forcing on land surface modeling results will be compared against observations in topographically heterogeneous regions.