Data for impacts of topography-based subgrid scheme and downscaling of atmospheric forcing on modeling land surface processes in the conterminous US

The effects of small-scale topography-induced land surface heterogeneity are not well represented in current Earth System Models (ESMs). A topography-based subgrid structure and methods of downscaling of atmospheric forcing from the atmospheric grid to the subgrids of the land model grid (TGUs) have been implemented in the Energy Exascale Earth System Model (E3SM) Land Model (ELM) to improve representation of the effects of small-scale topography-induced land surface heterogeneity on land surface processes. This study evaluates the impacts of the topography-based subgrid structure and downscaling of atmospheric forcing on modeling land surface processes in E3SM over the conterminous United States (CONUS). For this purpose, ELM simulations are performed using two configurations without (NoD ELM) and with (D ELM) downscaling, both using TGUs derived for the 0.5-degree grids and the same land surface parameters. Simulations using the two ELM configurations are compared over the CONUS domain, regional levels, and at observational sites (e.g., SNOTEL). The CONUS-level results suggest that D ELM simulates more snowfall and snow water equivalent (SWE), higher runoff, and less ET during spring and summer. Regional-level results suggest more pronounced impacts of downscaling over regions dominated by higher elevation TGUs and regions with maximum precipitation occurring during cool seasons. Results at the SNOTEL sites suggest that D ELM has superior capability of reproducing the observed SWE at 83% of the sites, with more pronounced performance over topographically heterogeneous TGUs with their maximum precipitation occurring during cool seasons. The results highlight the importance of improving representation of small-scale surface heterogeneity in ESMs and motivate future research to understand their effects on land-atmosphere interactions, streamflow, and water resources management over mountainous regions.

The data utilized to evaluate effects of the topography-based subgrid structure and downscaling of atmospheric forcing in land surface modeling include a TGU level land surface data file, atmospheric forcing to drive the land model, ELM user name list configuration parameters, regionalization variables (topographic regions, snow fraction regions, water versus energy limited regions, and regions of season of maximum precipitation), model restart files for both ELM configurations, and model outputs (grid and subgrid levels), model outputs aggregated to TGUs and grid levels.

The data files include:

DELM.zip: Directory containing the following files relevant to the D ELM configuration and model output files.

Restart file: 202201289.tgu_all_disag_yr1850surfdata.ielm.r05_r05.compy.elm.r.2005-01-01-00000.nc

Configuration file: user_nl_elm

Aggregated grid-level monthly output file:  grd_level_output_disag_mnly_run_11_new_20221109.nc

Aggregated grid-level daily output file: grd_level_output_disag_daily_20220512.nc

TGU-level monthly output file: tgu_level_output_all_disag_20221109.nc

 NoDELM.zip: Directory containing the following files relevant to the NoD ELM configuration and model output files.

Restart file: 202201289.tgu_no_disag_yr1850surfdata.ielm.r05_r05.compy.elm.r.2005-01-01-00000.nc

Configuration file: user_nl_elm

Aggregated grid-level monthly output file: grd_level_output_nodisag_mnly_run_11_new_20221109.nc

Aggregated grid-level daily output file: grd_level_output_nodisag_daily_20220512.nc  

TGU-level monthly output file: tgu_level_output_no_disag_20221109.nc

shared.zip: Directory containing the following files relevant to both the D ELM and NoD ELM configurations.

Subgrid-based surface data file: MASKED.half_degree_merge.surfdata_0.5x0.5_simyr1850_c200924.pft17.10262022v2.nc

Regionalization file used to generate regions based on snow fraction, water versus energy limited state, and seasons of maximum precipitation: half_deg_budyko_curve_analysis_20230104_disag.nc

Topographic ratio file used to generate topography-based regions: grd_level_output_nodisag_run_11_new_20221109.nc

TGU-level surface elevation data file where surface elevation data are derived from high resolution surface elevation data (90 m) obtained from HydroSHEDS [Lehner et al. 2008, Lehner and Grill 2013]:  half_deg_subgrids_with_PFTs_and_stat_20210403.nc

SNOTEL_files.zip: Directory containing the following SNOTEL data related files used to evaluate model performance.

 SNOTEL list of stations file: SNOTEL_halfdegree_intersect4.csv

SNOTEL data files/folders: csv

References

Lehner, B., et al. (2008). "New Global Hydrography Derived From Spaceborne Elevation Data." Eos, Transactions American Geophysical Union 89(10): 93-94.

Lehner, B. and G. Grill (2013). "Global river hydrography and network routing: baseline data and new approaches to study the world's large river systems." Hydrological Processes 27(15): 2171-2186.