Journal
JOURNAL OF ADVANCES IN MODELING EARTH SYSTEMS
Volume 14, Issue 4, Pages -Publisher
AMER GEOPHYSICAL UNION
DOI: 10.1029/2021MS002862
Keywords
sub-grid heterogeneity; sub-grid topography; surface energy balance; surface boundary conditions; E3SM; ELM
Categories
Funding
- U.S. Department of Energy (DOE), Office of Science, Office of Biological and Environmental Research, Earth System Model Development program area, as part of the Climate Process Team projects
- Atmospheric Administration (NOAA) [NOAA-OAR-CPO-2019-2005530, NA19OAR4310243]
- National Science Foundation
- DOE [DE-AC05-76RL01830]
- Office of Science of the DOE
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This study analyzed and evaluated the impacts of sub-grid topographic representations on surface energy balance and boundary conditions. The results showed that sub-grid topographic effects have significant impacts on surface energy balance and boundary conditions, and the T configuration better captured these effects.
Sub-grid topographic heterogeneity has large impacts on surface energy balance and land-atmosphere interactions. However, the impacts of representing sub-grid topographic effects in land surface models (LSMs) on surface energy balance and boundary conditions remain unclear. This study analyzed and evaluated the impacts of sub-grid topographic representations on surface energy balance, turbulent heat flux, and scalar (co-)variances in the Energy Exascale Earth System Model (E3SM) land model (ELM). Three sub-grid topographic representations in ELM were compared: (a) the default sub-grid structure (D), (b) the recently developed sub-grid topographic structure (T), and (c) high spatial resolution (1KM). Additionally, two different solar radiation schemes in ELM were compared: (a) the default plane-parallel radiative transfer scheme (PP) and (b) the parameterization scheme (TOP) that accounts for sub-grid topographic effects on solar radiation. A series of offline simulations with the three grid discretization structures (D, T, and 1KM) and two schemes of solar radiation (TOP and PP) were carried out using the Sierra Nevada, California. 1KM simulations with TOP well capture the spatial heterogeneity of surface fluxes compared to Moderate Resolution Imaging Spectroradiometer remote sensing data. There are significant differences between TOP and PP in the 1-km simulated surface energy balance, but the differences in mean values and standard deviations become small when aggregated to the grid scale (i.e., 0.5 degrees). The T configuration better mimics the 1KM simulations with TOP than the D configuration and better captures the sub-grid topographic effects on surface energy balance and boundary conditions. These results underline the importance of representing sub-grid topographic heterogeneities in LSMs and motivate future research to understand the sub-grid topographic effects on land-atmosphere interactions over mountainous areas.
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