Comparison of  Sensible and Latent Heat Fluxes Estimated by the Eddy Covariance Method and the Flux Variance Method

2007

M. H. Li, K. Z. Wei, and Y. F. Yuan

Institute of Hydrological Sciences, National Central University, Taoyuan, Taiwan

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Sensible heat and latent heat fluxes estimated by the Eddy Covariance Method (ECM) and the Flux Variance Method (FVM) are compared in this study. Flux measurements were conducted at an experimental site with periodically trimmed short grass at the National Central University. Turbulence data were measured by a 3-D sonic anemometer (81000, Young) and a krypton hydrometer (KH20, Campbell) at 10 Hz and stored by a data logger (CR23X, Campbell) and a laptop computer. Net radiation, soil heat flux, soil moisture, soil temperature, and air pressure were also measured and stored every 10 minutes by another data logger. A total of 5 experimental periods were performed between September 2006 and January 2007 ranging from 4 days to 21 days. Only non-rainfall raw data between 1000 and 1400 local time examined through despike, detrend, and double rotation were applied for flux calculations. Energy closure of the ECM is examined by the Energy Balance Ratio. The EBRs of the ECM are 0.85 in 2006 and 0.83 in 2007. Latent heat fluxes computed by the FVM are consistently higher than those by the ECM. Most of sensible heat fluxes computed by the FVM are also higher than those by the ECM. The correlation of sensible heat fluxes between the ECM and the FVM is higher than that of latent heat fluxes.