GRADIENT MEASUREMENTS OF METHANE FLUX IN LIN'AN RICE PADDIES

From July to September of 1990,CHflux measurements were made in Lin’an rice paddies using gradient profiletechniques.Some characteristics of the turbulence structure under the stable conditions have been verified in the surfacelayer according to the in situ measurements.The semi-empirical turbulent parameters β,βand βand their changeswith the stability parameter Ri are given.Observed results indicate that CHflux in the rice-paddy is mainly decided bythe methnogenesis and the process of CH4 transport from internal soils to the atmosphere,and that the CHverticaltransfer is depressed in the stable surface layer.The CHflux shows that its obvious diurnal changes,and the meanCHflux are higher in nighttime and lower in daytime,and the peaks appear at about 2000 BST at night and 0300 BSTin the early morning,respectively.The mean value of CHflux is about 4.18±2.3 mg/m~2 h.