Significant Decrease of Uncertainties in Sensible Heat flux Simulation Using Temporally Variable Aerodynamic Roughness in Two Typical Forest Ecosystems of China

Aerodynamic roughness length z(om) is an important parameter for reliably simulating surface fluxes. It varies with wind speed, atmospheric stratification, terrain, and other factors. However, it is usually considered a constant. It is known that uncertainties in z(om) result in latent heat flux (LE) simulation errors, since z(om) links LE with aerodynamic resistance. The effects of z(om) on sensible heat flux (SH) simulation are usually neglected because there is no direct link between the two. By comparing SH simulations with three types of z(om) inputs, it is found that allowing z(om) temporal variation in an SH simulation model significantly improves agreement between simulated and measured SH and also decreases the sensitivity of the SH model to the heat transfer coefficient C-t which in turn determines the linkage between Z(om) and thermal roughness length z(om)