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Abstract
Methane (CH4) is regarded as one of the most important greenhouse gases due to its radiative forcing. Therefore, in running climate models, it is important to have accurate estimates of CH4 concentrations at an appropriate scale. Although great efforts have recently been undertaken to quantify atmospheric CH4 concentrations based on extensive ground-based measurements, it is still difficult to obtain the spatial variations of the CH4 volume mixing ratio (VMR) on a regional scale. This study analyses the spatial variations of CH4 VMRs in China, based on the retrieved CH4 data from Scanning Imaging Absorption Spectrometer for Atmospheric Chartography (SCIAMACHY) spectra. The results showed that the spatial distribution of CH4 VMRs presented decreasing gradients from south-east to north-east and the lowest CH4 concentrations were located on the Qinghai-Tibet Plateau. Paddy fields were the main sources of CH4 in China, as shown through spatial analysis. Natural wetlands and population also contributed to CH4 VMRs. Plant, climate and soil properties presented a strong positive influence on CH4 concentrations, which could be used to interpret the spatial variations. Stepwise multiple regression modelling results showed that temperature, normalized difference vegetation index (NDVI) and soil total nitrogen could explain 76.9% of the differences in CH4 throughout China, and the average difference between the retrieved and the modelled methane concentrations was 14 ppb.
Acknowledgements
Funding support was partially from the Specialized Research Fund for the Doctoral Program of Higher Education of China (20100091120017) the Open Foundation of State Key Laboratory of Remote Sensing (OFSLRSS201013). The State Key International Cooperation Project (20073819), The State Key Fundamental Science Funds of China (2010CB950702 and 2010CB428503), the State High Technology Funds of China (2009AA122001 and 2009AA122005), the State Key Basic Research Funds of China (2007FY110300-04 and 08), NSF-China Project (40671132 and 30590383), and the Key Project of Zhejiang Province (2008C13G2100010).