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[B-4.3.4 Study on International Cooperative Observation Study of Flux Evaluation in Large Scale at Reference Field in Japan(Micrometeorological Measurements of Mass and Energy Exchange between a Rice Paddy and the Atmosphere)]

[Contact Person]

Yoshinobu HARAZONO
Head of Micrometeorology Lab.
National Institute of Agro-Environmental Sciences,
MAFF/Japan
Kannondai, Tsukuba, 305 Japan
Phone +81-298-38-8207, Fax +81-298-38-8211
E-mail yoshi4@niaes.affic.go.jp

[Total Budget for FY1996]

1,976,000 Yen

[Abstract]

　Field measurements of carbon dioxide(CO₂), water vapor(H₂O, latent heat IE), methane(CH₄) and heat fluxes(sensible H) were conducted at Hachihama Field, Okayama University in 1996 summer. Over the flooded rice field, CO₂, H₂O and heat fluxes were measured by an eddy correlation method and CH₄ flux was determined by modified gradient method.
　In order to get accurate flux numbers, the spectrum distribution of flux were examined on eddy correlation measurement and the line averaging effects of the fluctuations of concentrations and vertical wind speed was corrected. For methane flux, the level was examined comparing with the flux obtained by the Inverse Lagrangian method originally proposed by CSIRO, Australia group. From these examination flux levels include the spectrum correction were considered to be accurate compare to those exclude the corrections. The modified gradient method was also confirmed as more accurate method to determine the trace gas flux.
　The flux levels of CO₂ and H₂O were almost same as those obtained at similar vegetation previously. The measurement site was special field with weekly drainage. During the flooded period, water table suppressed transfer of CO₂ from soil layer, thus the CO₂ flux in flooded periods was smaller than that in drainage period.

[Key Words]

Carbon dioxide, flux, flooded rice field, micrometeorology