Atmospheric methane observed from space over the Asian monsoon: implications for emission from Asian rice paddies
Abstract
More than 40% of anthropogenic emissions of methane, the second most important greenhouse gas, is estimated to be from agricultural sources, including rice cultivation. Unfortunately, the strength of individual sources of methane remains uncertain, despite the importance of its effect in global warming. Here we focus on the Asian monsoon region to improve our understanding of methane emission from rice paddy fields. This region contains about 90% of the world’s rice fields. We analyze the temporal and spatial distribution of atmospheric methane concentrations observed from space and compare it with ground-based measurements and bottom-up emission inventory data coupled with rice field maps. Recently, Frankenberg et al. [2008] derived an updated version of methane concentration from the Scanning Imaging Absorption Spectrometer for Atmospheric Chartography (SCIAMACHY: SCIA hereafter) instrument onboard ENVISAT. This showed a clear signature of methane enhancement over the Asian monsoon. As SCIA retrievals include all involve column densities, we carefully examined potential biases and variability due to the gradient of methane concentration over source regions by comparing these data with ground-based measurements at 53 stations of the WDCGG network. After evaluating the bias and variability of methane concentration over the source regions, we examined selected areas where rice paddies were highly concentrated, and the methane emission inventories were estimated to be large. The sampled areas were North and South India, Bangladesh, Myanmar, Thailand, South China, and the Sichuan Basin. All of these are known to be major rice cultivation areas. The time series of monthly mean SCIA retrievals were compared with the emission inventory data for rice cultivation archived in the GISS dataset and Yan et al. [2009], as well as with precipitation data (Huffman et al., 1997). The phase of seasonal variation of SCIA retrievals corresponded closely to those of emission inventories. High methane concentrations were observed in the later period of the rainy season for each area. The amplitude of seasonal variation was large compared with the possible bias over the source regions, demonstrating the reliability of the analysis. We are planning to extend the analysis to the methane data observed by the Thermal And Near infrared Sensor for carbon Observations Fourier Transform Spectrometer (TANSO-FTS) onboard the Greenhouse gases Observing SATellite (GOSAT). GOSAT was launched successfully on January 23, 2009, and has been operating continuously since then. The TANSO-FTS will provide important information on methane emission from rice paddies with good spatial resolution (10 km in diameter). Preliminary results from this instrument will also be presented. References: Frankenberg, et al. (2008), Geophys. Res. Lett., 35, doi:10.1029/2008GL034300. Huffman et al. (1997), Bull. Am. Meteorol. Soc. Vol. 78, 5-20. Yan et al., (2009), Global Biogeochem. Cycles, 23, GB2002, doi:10.1029 /2008GB003299.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2010
- Bibcode:
- 2010AGUFM.A53D0281H
- Keywords:
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- 0315 ATMOSPHERIC COMPOSITION AND STRUCTURE / Biosphere/atmosphere interactions;
- 0365 ATMOSPHERIC COMPOSITION AND STRUCTURE / Troposphere: composition and chemistry