Satellite data based estimation of methane emissions from rice paddies in the Sanjiang Plain in northeast China

The Sanjiang Plain (SJP), one of the major rice producing regions in China, is an important source of methane (CH4) emissions. However, there have been large uncertainties in the estimates of CH4 emissions from this area during the past few years. In this study, we estimated CH4 emissions using a process-based model derived by rice area, CH4 flux, land surface temperature (LST), and the ratio of precipitation (P) and evapotranspiration (ET) in rice paddies in the SJP during the rice growing seasons in 2000, 2006, and 2010, respectively. The results showed that the total area of rice fields was 1.64 million ha in 2010, which was approximately 35 and 13% higher than in 2000 and 2006, respectively. The average LST was 22.1°C in 2000 which was higher than in 2006 (21.6°C) and 2010 (21.5°C). Monthly ET and P displayed similar seasonal and annual variability. The monthly ET was 61.7, 66.5, and 63.0 mm month-1 and P was 85.1, 80.6 and 85.9 mm month-1 during the rice growing seasons in 2000, 2006, and 2010, respectively. The averaged CH4 flux rates were 24.83, 24.63, and 24.59 ton km-2, and the estimated mean annual CH4 emissions from rice paddies were 0.30, 0.36, and 0. 40 Tg yr-1 in 2000, 2006, and 2010, respectively. The CH4 emissions displayed obvious spatial variations that decreased from east to west in the SJP, and were mainly affected by temperature. The results will improve our understanding of the inter-annual and spatial variations of CH4 emissions and provide a more accurate regional budget of CH4 emissions from rice paddies in the Sanjiang Plain.