Estimation of Gas Fluxes Using the Energy Balance Flux Ratio Method

To estimate CO2 and CH4 fluxes from an agricultural land accurately using the energy balance flux ratio method, first, the temperature difference and the mixing ratio difference between two heights, which are variables in the method, were corrected with the law of propagation of error. Next, the relationship between friction velocity and turbulent diffusion coefficient was obtained using data with relatively larger corrected temperature and mixing ratio differences, and fluxes were estimated using the turbulent diffusion coefficient calculated from the relationship. To verify the applicability of the method, the quantities of net photosynthesis calculated with estimated CO2 fluxes were compared with those calculated using the photon conversion efficiency (the increment of carbon content in plant per 1mol of photon). Both quantities coincided satisfactorily with 0.95 of proportional coefficient and 0.97 of correlation coefficient. In conclusion, gas fluxes from an agricultural land could be estimated satisfactorily using the energy balance flux ratio method if the gas concentration could be measured accurately.