Estimation of methane emission from rice paddy soils in Japan using the diagnostic ecosystem model

It is needed to accurately evaluate the methane emission from paddy fields at a national scale for both scientific and political purposes. The existing approaches have shared a common issue with obtaining the realistic information on spatiotemporal variations of crop management. Satellite sensor could possibly detect them, but the methodology to link the satellite observations to the methane emission has not been established. In this study, we enhanced the existing diagnostic satellite-driven paddy ecosystem model, the Biosphere model integrating Eco-physiological And Mechanistic approaches using satellite data for regional Cropland (BEAMS-C) (Sasai et al., 2012), by integrating the methane processes and examined the potential of this approach by comparing the estimated nation-wide methane emission with that by the existing approaches. The carbon flux estimations had good agreements with the measurements at the Mase paddy flux site. In regional-scale analyses in Japan, methane emission averaged from 2001 to 2010 was 15.0 gC m^-2 year^-1, which was similar to the Tire-1 and -2 results. If we have a continuing improvement of the diagnostic approach, it could be one of the most efficient tools for estimating the methane flux at national scales.