Analysis On Global Carbon Fluxes Based On GOSAT Data

The global warming induced by CO2emission has aroused great public concern. The assessments of the CO2sources and sinks and the accurate prediction of future atmospheric CO2concentrations are of great significance. With the rapid development of the remote sensing satellite, its status in observations of CO2concentration of global carbon cycling is become more and more important. In order to improve the precision of the CO2observation, a Japanese satellite, Greenhouse gases Observing SATellite (GOSAT) was launched successfully on January23rd,2009. The GOSAT has released a series of products during the past several years, which become the most important data to study the carbon flux and relieve the Greenhouse issue.In our study, we derived a biosphere flux datasets named NEEGOSAT based on GOSAT L4A grid data (1°×1°) product, and developed the work on it. We compared NEEGOSAT with the model result of CASA (NEECASA), and validated it using the Ameriflux sites data. We analyzed the monthly variation and spatial distribution of the global NEEGOSAT from June2009to October2011. We also analyzed the flux variations of the continent and country, and calculated their total carbon flux. The main works and conclusions of this paper are listed as following:(1) The comparison of NEEGOSAT and NEECASA shows that although the calculated global total flux and the amplitude of the NEEGOSAT variation is larger than NEECASA, their spatial distribution and month variation are in good agreement and their monthly data show a high correlation. The validation of NEEGOSAT, based on Ameriflux sites data, indicates that judging from the average, the forest flux observation sites data shows a good relation with NEEGOSAT while the result of savannas is relatively poor.(2) From the comparison, validation and analysis of NEEGOSAT, we found that there are several reasons for the disagreement between NEEGOSAT and the other two kinds of data,(a) The spatial resolution of the applied data is different.(b) The uncertainties of GOSAT data are existed.(c) There are also uncertainties caused by model inversion, including the uncertainties of CASA model and the IGCCMS (Integrated global carbon cycle modeling system) which is used to the GOSAT flux data inversion.(3) The analysis of NEEGOSAT from June2009to October2011demonstrates that the spatial distribution characters of NEEGOSAT are significantly related to the land cover types and climate types. The strong carbon sink mostly distributed in forests land while a strong carbon source can be found in savannas land. In terms of temporal variation, the carbon sinks often appeared in growing season while carbon source during non-growing season.(4) The estimates of NEEGOSAT data indicate that the global area was net sinks from June2009to October2011. It sunk-2.54Pg C yr-1during the period from June2009to May2010, and sunk-3.49Pg C yr-1from June2010to May2011. The average global carbon sequestration of the two years was-3.02Pg C yr-1. All the continents were net carbon sinks except Africa (0.35Pg C yr-1). Compared with other continents, Asia sunk the largest amount of carbon of-1.05Pg C yr-1, followed by North America (-0.82Pg C yr-1). Europe and South America were approximate, sunk about-0.65Pg C yr-1and-0.55Pg C yr-1, respectively. Oceania took in-0.30Pg C yr-1. We also estimated the carbon flux of several countries, including Russia, Canada, China, America, Australia, Brazil and Japan. America and China sunk the largest amount of carbon of-0.56Pg C yr-1. Brazil sunk-0.54Pg C yr-1while Russia took in-0.48Pg C yr-1. Canada and Australia were similar, sunk about-0.26Pg C yr-1. Japan was approximately in carbon balance, sunk-0.02Pg C yr-1.