Surface energy balance at heterogeneous sites have been examined using eddy covariance measurement and other observations measured at 1 industrial site and 3 agricultural sites near the Nakdong river. Energy balance closure was evaluated by calculating long-term averaged energy balance ratio (EBR) and statistical regression of turbulent energy fluxes against available energy (a sum of net radiation and ground heat flux) with half-hourly data. EBR of all sites ranges from 0.47 to 0.86 during daytime and from ?0.30 to 0.21 during nighttime. The mean coefficient of determination was 0.63 and 0.10 during daytime and nighttime, respectively. Energy balance closure was poor particularly during nighttime because measurement source areas for turbulent fluxes and available energy do not match each other at heterogeneous sites during nighttime. The unmeasured heat storage term seem to play a role in surface energy budget in industrial site and irrigated site showing low EBR at these sites. Energy balance closure was better in conditions of high wind speed, low downward short wave radiation and high friction velocity, possibly suggesting the role of heat storage term and surface heterogeneity in surface energy balance at these sites. The correction of ground heat flux increases EBR about 10 % and results in change of coefficient of determination by less than 5 %, suggesting that underestimated ground heat flux is not a main factor in poor EBR at these sites.
Spectrum analysis shows a sharp roll-off at the low frequency in co-spectrum indicating that low-frequency motions do not contribute to turbulent fluxes significantly. Both spectra and co-spectra in unstable conditions show broad peak indicating the influences of multiple sizes of large eddies over heterogeneous sites. In stable conditions, spectra of u, T and q show two prominent peaks. Ogive analysis for the latent and sensible heat fluxes show that the ogive curve reaches an asymptote at 30 minutes, indicating that there is no more flux beyond 30 min. However, there is possibility of heat transfer by stationary eddy in weak wind conditions, which is not detected in this analysis.