To elucidate the seasonal and inter-annual variation of CO(2) exchanges between the atmosphere and cultivated field in Japan, the CO(2) flux has been measured by the eddy correlation technique at the experimental farm of Agricultural Faculty, Okayama University since December in 1998. The CO(2) sensor, however, does not work under rainy conditions. The improved aerodynamic technique was developed and used to cover CO(2) flux data which were not collected. This technique gives reasonable CO(2) fluxes even in rainy days. The reliability of the technique was also confirmed by comparing CO(2) fluxes with those measured by the eddy correlation technique using data in fine weather conditions
