Abstract
Flux variance (FV) method is considered as a simple method for estimating surface fluxes of sensible and latent heat flux (H
and LE, respectively). The FV method estimates sensible heat flux from high frequency temperature measurements using a
fine wire thermocouple. Additional measurements of net radiation and soil heat flux, allow the derivation of latent heat flux
as the residual of the energy balance closure. In this study, fine wire thermocouples were deployer over dense canopy of
Camellia sinensis, at five measurement heights above the plant canopy, one in the roughness sublayer and four at higher levels
in the inertial sublayer. In addition, reference measurements of H and LE were conducted by an Eddy Covariance (EC) system
consisted of a 3D ultrasonic anemometer and an open path analyzer. The data collection was done during Sep-Nov 2018 where
only the half-hourly dataset under unstable condition was investigated. Results showed better performance of the FV in the
inertial sublayer as compared to the roughness sublayer. Estimations of H at (h2 = 1.5m and h3 = 2m) were in reasonable
agreement with EC measurements of H, with coefficient of determination of R2 = 0.82 and R2 = 0.81, respectively. The
estimation of latent heat flux was in good agreement with the EC method and the highest R2= 0.89 was obtained at h2. Overall,
the FV method performed well for the estimation of surface fluxes within the inertial sublayer, while the best results were
obtained at a height of 2.5-3 times the canopy height.
