NUMERICAL SIMULATION OF CH₄ EMISSION FROM RICE PADDY FIELDS DURING RECENT 50 YEARS

Based on the DNDC model of American, a numerical model for simulating CH₄ emission from rice paddy fields is established. Validation of the model with the observed data shows that the mean relative error is about 15%. The simulation analysis results show that the CH₄ emission is interrelated well with average temperature during rice growth periods. Analysis of CH₄ emission and meteorological factors by using power spectrum indicates that the change of CH₄ emissions has 4-5 year cycles, which is the same as that of temperature. Simple statistical models are given based on the results of the numerical model, which can be applied conveniently to estimate and monitor CH₄ emissions in the rice paddy fields.