Changes in Flux Profiles of Heat, Water Vapor, and CO2 in the Atmospheric Surface Layer with Soil Moisture Under the Influence of Large Eddies: Implication for the Energy Balance Closure Issue

Coupling of land-surface and boundary layer processes has become increasingly recognized. However, it remains less studied as to how such coupling affects fluxes of sensible (H) and latent (LE) heat and CO₂ in the atmospheric surface layer (ASL) under different soil moisture conditions. Here it is demonstrated that H in the ASL is always underestimated for all the soil moisture conditions with Bowen ratio (β) from 0.51 to 1.91, and LE is underestimated for β < 0.60 but overestimated for β > 0.60 due to changes in asymmetric contributions of sweeps and ejections to fluxes as soil moisture decreases. As a result, the non-closure of the surface energy balance improves as soil moisture decreases. The non-closure does not necessarily mean that CO₂ is also underestimated. Rather, CO₂ flux in the ASL becomes overestimated as β > 0.2 under which non-closure still exists.