Impact of the biomass burning on methane variability during dry years in the Amazon measured from an aircraft and the AIRS sensor.

The present study examines the spatiotemporal variability and interrelations of the atmospheric methane (CH), carbon monoxide (CO) and biomass burning (BB) outbreaks retrieved from satellite data over the Amazon region during the 2003-2012 period. In the climatological context, we found consistent seasonal cycles of BB outbreaks and CO in the Amazon, both variables showing a peak during the dry season. The dominant CO variability mode features the largest positive loadings in the southern Amazon, and describes the interannual CO variations related to BB outbreaks along the deforestation arc during the dry season. In line with CO variability and BB outbreaks, the results show strong correspondence with the spatiotemporal variability of CH in the southern Amazon during years of intense drought. Indeed, the areas with the largest positive CH anomalies in southern Amazon overlap the areas with high BB outbreaks and positive CO anomalies. The analyses also showed that high (low) BB outbreaks in the southern Amazon occur during dry (wet) years. In consequence, the interannual climate variability modulates the BB outbreaks in the southern Amazon, which in turn have considerable impacts on CO and CH interannual variability in the region. Therefore, the BB outbreaks might play a major role in modulating the CH and CO variations, at least in the southern Amazon. This study also provides a comparison between the estimate of satellite and aircraft measurements for the CH over the southern Amazon, which indicates relatively small differences from the aircraft measurements in the lower troposphere, with errors ranging from 0.18% to 1.76%.