Surface Exchange of Energy and Carbon Dioxide between the Atmosphere and a Farmland in Haenam, Korea

Surface energy and CO2 fluxes have been measured over a farmland in Haenam, Korea since July 2002. Eddy covariance technique, which is the only direct flux measurement method, was employed to quantitatively understand the interaction between the farmland ecosystem and the atmospheric boundary layer. Maintenance of eddy covariance system was the main concern during the early stage of measurement to minimize gaps and uncertainties in the dataset. Half-hourly averaged CO 2 concentration showed distinct diurnal and seasonal variations, which were closely related to changes in net ecosystem exchange (NEE) of CO2. Daytime maximum CO2 uptake was about -1.0 mg CO2 m -2 s -1 in August whereas nighttime CO2 release was up to 0.3 mg CO2 m -2 s -1 during the summer. Both daytime CO2 uptake and nighttime release decreased gradually with season. During the winter season, NEE was from near zero to 0.05 mg CO2 m -2 s -1 . FK site was a moderate sink of atmospheric CO 2 until September with daily NEE of 22 g CO2 m -2 d -1 . In October, it became a weak source of CO2 with an emission rate of 2 g CO2 m -2 d -1 . Long-term flux measurements will continue at FK site to further investigate inter-annual variability in NEE. To better understand these exchange mechanism and in-depth analysis, process-level field experiments and intensive short-term intercomparisons are also expected to be followed.

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