Estimation of Methane Emission from Paddy Fields in Central Plain of Thailand by Scaling Technique

Since the rapid increase in atmospheric methane was recognized in the early 1980’s, paddy fields have been considered to be one of the likely and most important sources of this problem. The objective of this study is to estimate the methane emission from paddy fields with remotely sensed data and the methane flux in situ. In this paper, firstly, we developed a scaling technique to extrapolate the local information on land cover type combination from high spatial resolution data (OPS) to more extensive area through low spatial resolution data (AVHRR) with wide coverage. Paddy field area was extracted from OPS data, then AVHRR NDVI was statistically regressed with the corresponding paddy area ratio from OPS pixels for corresponding AVHRR pixel. With this regression model (scaling model), local information of the paddy area was estimated only from AVHRR data over extensive area outside the OPS data. Secondly, this method is applied to the paddy field extraction in the Central Plain of Thailand. Finally, we estimated the methane emission from paddy fields by multiplying observed in situ methane flux and the total paddy area estimated in whole AVHRR.