Gatti, Luciana V; Correa, Caio C S; Domingues, Lucas G; Miller, John B; Gloor, Manuel; Martinewski, Alexandre; Basso, Luana Santamaria; Santana, Ricardo; Crispim, Stephane P; Marani, Luciano; Neves, Raiane Lopes (2021): CH4 Aircraft Vertical Profiles Measurements at Four Amazonian Sites Between 2010 and 2018 [dataset]. PANGAEA, https://doi.org/10.1594/PANGAEA.934596

To improve diagnosis of Amazonia's carbon cycle, starting in 2010, we initiated regular observation of lower troposphere CH4 concentrations at four aircraft vertical profiling sites spread over the Brazilian Amazonia. The four sites from the CARBAM project at Amazonia: SAN (2.86S 54.95W); ALF (8.80S 56.75W); RBA (9.38S 67.62W); TAB (5.96S 70.06W) was from 2010 to 2012 and TEF (3.39S 65.6W), started in 2013. The sampling period was typically twice per month (Gatti et al., 2014; Basso et al., 2016; Miller et al., 2007; d'Amelio et al., 2009; Domingues et al., 2020). Over nine-years, 590 vertical profiles were performed in a descending spiral profile from 4420 m to 300 m a.s.l. A mean of 75 vertical profiles was performed per year from 2010 to 2018 at the 4 sites, except for 2015 and 2016. In 2015 the flight collection was stopped in April at all sites, returning only in November at RBA. In 2016 only RBA and ALF were measured. The vertical profiles were usually taken between 12:0 and 13:00 local time. Air is sampled by semi-automatic filling of 0.7 L boro-silicate flasks inside purpose-built suitcases (PFP -Programmable Flask Package) (Tans et al., 1996); there are two versions, one with 17 flasks at SAN, and another with 12 flasks at TAB_TEF, ALF and RBA. This suitcase is connected to a compressor package (PCP –Portable Compressor Package), containing batteries and 2 compressors, which is connected to an air inlet on the outside of the aircraft at wing or window, depending on the aircraft model. Once a PFP (i.e. one vertical profile) has been filled with air the PFP is transported (from 2010 to 2014) to the IPEN (Instituto de Pesquisas Energéticas e Nucleares) Atmospheric Chemistry Laboratory in Sao Paulo, Brazil and since 2015 to the INPE/ LaGEE(Instituto Nacional de Pesquisas Espaciais/Greenhouse Gases Laboratory), in Sao Jose dos Campos, Sao Paulo state, Brazil. This laboratory is a replica of the NOAA/ESRL/GMD trace gas analysis system at Boulder, Colorado, USA, and was constructed in 2003 and sent to IPEN where started the analysis in 2004. The CH 4 analysis system is an FID (Flame Ionization Detector) chromatography (HP6890 Plus+ model) with pre-column of 198 cm of length and 3/16” o.d. (Silica Gel 80/100 mesh), a column of 106 cm of length and 3/16” o.d. (Molecular Sieve 5A 80/100 mesh), and a 12 mL volume sample loop (see Basso et al. 2016 for a detailed description). In order to assess the accuracy and long-term repeatability of the CH4 measurements, a previously calibrated sample is measured as an unknown in the system regularly. These results indicate long-term repeatability (one sigma) of 1.0 ppb. An inter-comparison between INPE and NOAA of weekly measurements at NAT (Brazilian northeast coast site) had a mean difference of 0.24±2.67 ppb (r = 0.98).