Interpreting Temporal Changes of Atmospheric CO2 Over Fire Affected Regions Based on GOSAT Observations

The carbon dioxide (CO2) emissions released from biomass burning significantly affect the temporal variations of atmospheric CO2 concentrations. Based on a long-term (July 2009-June 2015) retrieved data sets by the greenhouse gases observing satellite (GOSAT), the seasonal cycle and interannual variations of column-averaged volume mixing ratios of atmospheric carbon dioxide (XCO2) in four fire affected continental regions were analyzed. The results showed that Northern Africa (NA) had the largest seasonal variations after removing its regional trend of XCO2 with peak-to-peak amplitude of 6.2 ppm within the year, higher than central South America (CSA) (2.4 ppm), Southern Africa (SA) (3.8 ppm), and Australia (1.7 ppm). The detrended regional XCO2 (Delta XCO2) was found to be positively correlated with the fire CO2 emissions during the fire activity period but with different seasonal variabilities. NA recorded the largest change of seasonal variations of Delta XCO2 with a total of 12.8 ppm during fire seasons, higher than CSA, SA, and Australia with 5.4, 6.7, and 2.2 ppm, respectively. During the fire episode, the positive Delta XCO2 was noticed during June-November in CSA, December to next June in NA, and May-November in SA. The Pearson correlation coefficients between the variations of Delta XCO2 and fire CO2 emissions achieved the best correlations in SA (R = 0.77 and p < 0.05). This letter revealed that fire CO2 emissions and GOSAT XCO2 presented consistent seasonal variations.