Methane airborne measurements and comparison to global models during BARCA

Tropical regions, especially the Amazon region, account for large emissions of methane (CH₄). Here, we present CH₄ observations from two airborne campaigns conducted within the BARCA (Balanço Atmosférico Regional de Carbono na Amazônia) project in the Amazon basin in November 2008 (end of the dry season) and May 2009 (end of the wet season). We performed continuous measurements of CH₄ onboard an aircraft for the first time in the Amazon region, covering the whole Amazon basin with over 150 vertical profiles between altitudes of 500 m and 4000 m. The observations support the finding of previous ground‐based, airborne, and satellite measurements that the Amazon basin is a large source of atmospheric CH₄. Isotope analysis verified that the majority of emissions can be attributed to CH₄ emissions from wetlands, while urban CH₄ emissions could be also traced back to biogenic origin. A comparison of five TM₅ based global CH₄ inversions with the observations clearly indicates that the inversions using SCIAMACHY observations represent the BARCA observations best. The calculated CH₄ flux estimate obtained from the mismatch between observations and TM5‐modeled CH₄ fields ranges from 36 to 43 mg m−2d−1 for the Amazon lowland region.