Capturing finer-scale topographic differences improves the ability of Earth system models to reproduce observations

Spatial pattern of number of topographic units (TGU) per 0.5 degree grid. We demonstrate the ability of a terrain-based subgrid structure to capture terrain heterogeneity across a mountainous region and associated data that is a measure of the computational efficiency of the data reduction metric (DRM). We define a variable number of TGUs per grid in conjunction with the allocation of a maximum number of TGUs per grid (12 in this study). Credit: Journal of Advances in Modeling Earth Systems (2024). DOI: 10.1029/2023MS004064
Earth system models (ESMs) used in climate simulation and forecasting typically use grids with resolutions of 50 to 200 km. These are relatively coarse and are thought to have limited ability to resolve surface variations.
To enhance the ESM’s ability to simulate the effects of small-scale land surface differences, a new subgrid structure was introduced in the new study. The researchers also used techniques to downscale atmospheric variables such as precipitation and temperature from atmospheric grids to subgrid terrain units established in previous studies of the Energy Exascale Earth System Model (E3SM) Land Model (ELM). I also used
The research is published in the Journal of Advances in Modeling Earth Systems.
Analysis of ELM simulations with and without new surface subgrids and downscaled atmospheric variables revealed significant effects on snowfall, snowwater equivalent, and runoff. These results were particularly pronounced in regions that are predominantly mountainous and experience the greatest precipitation during the cool season.
This new development significantly enhances ELM’s ability to reproduce measurements of snow water equivalent (i.e., the amount of liquid water held in snow) at snow telemetry (SNOTEL) sites in the western United States. Ta.
By improving ELM’s ability to reproduce observed snowwater equivalents at 83% of SNOTEL sites across the western United States, this study provides new tools for understanding the regional and global water cycle and its future changes. Motivating model functionality to be incorporated into E3SM. . This provides the basis for more effective water management plans and actions.
The impact of new developments on the simulation of land surface processes was evaluated using the contiguous (i.e., contiguous) United States (CONUS) as a case study. ELM simulations with new developments generally increased snowfall, snowwater equivalent, and runoff over CONUS. The impact of new development was found to be greater in regions where high-altitude landscapes predominate and where precipitation is greatest during the cool season.
The new development also improved the ELM’s ability to reproduce the snow water equivalent observed at the SNOTEL site, contributing to an overall improvement in the model’s predictive accuracy. The results of this study have important implications for modeling mountain stream flow and water resource management, both of which are strongly influenced by hydrological processes in mountain regions.
Further information: Teklu K. Tesfa et al, Impacts of Topography-Based Subgrid Scheme and Downscaling of Atmospheric Forces on Modeling Land Surface Processes in the Conterminous US, Journal of Advances in Modeling Earth Systems (2024). DOI: 10.1029/2023MS004064
Provided by Pacific Northwest National Laboratory
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