Simulating surface energy fluxes using the variable-resolution Community Earth System Model (VR-CESM)

We used two eddy covariance tower clusters in the Eastern USA to evaluate surface energy fluxes (latent heat, λE; sensible heat, H; net radiation, Rn; and ground heat, G) and surface properties (aerodynamic resistance to heat transfer, raero; Bowen ratio, β; and albedo, α) by uncoupled point simulations of the land-only Community Land Model (PTCLM4.5) and two coupled land–atmosphere Community Earth System Model (CESM1.3) simulations.

The CESM simulations included a 1° uniform grid global simulation and global 1° simulation with a 0.25° refined VR grid over the Eastern USA. Tower clusters included the following plant functional types—broadleaf deciduous temperate (hardwood) forest, C3 non-Arctic grass (grass), a cropland, and needleleaf evergreen temperate (pine) forest. During the growing season, diurnal cycles of λE and H for grass and the cropland were simulated well by PTCLM4.5 and VR-CESM1.3; however, λE (H) was biased low (high) at the hardwood and pine-forested sites, contributing to biases in β.