Estimate of methane release from temperate natural wetlands using ENVISAT/SCIAMACHY data in China

Since wetlands are the largest natural sources of atmospheric CH4, it is important to estimate the CH4 emissions from natural wetlands at regional scale and over a long time period. The annual CH4 efflux from temperate natural wetlands excluding water surface in China was estimated, based on atmospheric CH4 concentrations from SCIAMACHY/ENVISAT. The atmospheric CH4 concentrations showed obvious seasonal cycles, and CH4 emission from natural wetlands dominated the temporal variations of CH4 concentrations in north China, accounting for about 67.94% of the variations of CH4 concentrations. The chemical transport model, MOZART-4 (Model for Ozone and Related Chemical Tracers, version 4), was used to simulate the space-borne CH4 column concentrations to the surface level, and then the relationship between surface concentrations and emissions of CH4 from natural wetlands was simulated by a linear regression model. The results showed that the estimated annual budget of CH4 emission from natural wetlands in the temperate zone of China was about 4.76 Tg CH4, which was within the range of 2.38–4.91 Tg CH4 estimated by spatial distribution of wetland and the published CH4 release fluxes during the 1990s–2000s. This demonstrated that the method of using space-borne CH4 column concentrations to estimate CH4 emissions from natural wetlands was reliable.

► Natural wetland emission dominates seasonal variation of atmospheric CH4. ► MOZART-4 is used to simulate the space-borne XCH4 columns to the surface level. ► Relationship between surface CH4 concentrations and emissions from wetland is simulated by a linear regression model. ► The estimated CH4 emission from natural wetlands in temperate zone of China is 4.76 Tg CH4 yr−1.