@Article{DominguesGASCGPMTSMCNC:2020:NeBaMe,
               author = "Domingues, Lucas Gatti and Gatti, Luciana Vanni and Aquino, Afonso 
                         and Sanchez Ipia, Alber Hamersson and Correira, Caio and Gloor, 
                         Manuel and Peters, Wouter and Miller, John and Turnbull, Jocelyn 
                         and Santana, Ricardo and Marani, Luciano and C{\^a}mara, Gilberto 
                         and Neves, Raiane Aparecida Lopes and Crispim, St{\'e}phane 
                         Palma",
          affiliation = "{Instituto de Pesquisas Energ{\'e}ticas e Nucleares (IPEN)} and 
                         {Instituto Nacional de Pesquisas Espaciais (INPE)} and 
                         {Comiss{\~a}o Nacional de Energia Nuclear (CNEN)} and {Instituto 
                         Nacional de Pesquisas Espaciais (INPE)} and {Instituto de 
                         Pesquisas Energ{\'e}ticas e Nucleares (IPEN)} and {University of 
                         Leeds} and {University of Groningen} and {National Oceanic and 
                         Atmospheric Administration (NOAA)} and {GNS Science} and 
                         {Instituto Nacional de Pesquisas Espaciais (INPE)} and {Instituto 
                         Nacional de Pesquisas Espaciais (INPE)} and {Instituto Nacional de 
                         Pesquisas Espaciais (INPE)} and {Instituto Nacional de Pesquisas 
                         Espaciais (INPE)} and {Instituto Nacional de Pesquisas Espaciais 
                         (INPE)}",
                title = "A new background method for greenhouse gases flux calculation 
                         based in back-trajectories over the Amazon",
              journal = "Atmosphere",
                 year = "2020",
               volume = "11",
               number = "7",
                pages = "e734",
                month = "July",
             keywords = "Amazon, Greenhouse Gases, background calculation.",
             abstract = "The large amount of carbon stored in trees and soils of the Amazon 
                         rain forest is under pressure from land use as well as climate 
                         change. Therefore, various efforts to monitor greenhouse gas 
                         exchange between the Amazon forest and the atmosphere are now 
                         ongoing, including regular vertical profile (surface to 4.5 km) 
                         greenhouse gas measurements across the Amazon. These profile 
                         measurements can be used to calculate fluxes to and from the rain 
                         forest to the atmosphere at large spatial scales by considering 
                         the enhancement or depletion relative to the mole fraction of air 
                         entering the Amazon basin from the Atlantic, providing an 
                         important diagnostic of the state, changes and sensitivities of 
                         the forests. Previous studies have estimated greenhouse gas mole 
                         fractions of incoming air ('background') as a weighted mean of 
                         mole fractions measured at two background sites, Barbados 
                         (Northern Hemisphere) and Ascension (Southern hemisphere) in the 
                         Tropical Atlantic, where the weights were based on sulphur 
                         hexafluoride (SF6) measured locally (in the Amazon vertical 
                         profiles) and at the two background sites. However, this method 
                         requires the accuracy and precision of SF6 measurements to be 
                         significantly better than 0.1 parts per trillion (picomole 
                         mole-1), which is near the limit for the best SF6 measurements and 
                         assumes that there are no SF6 sources in the Amazon basin. We 
                         therefore present here an alternative method. Instead of using 
                         SF6, we use the geographical position of each air-mass 
                         back-trajectory when it intersects the limit connecting these two 
                         sites to estimate contributions from Barbados versus Ascension. We 
                         furthermore extend the approach to include an observation site 
                         further south, Cape Point, South Africa. We evaluate our method 
                         using CO2 vertical profile measurements at a coastal site in 
                         Brazil comparing with values obtained using this method where we 
                         find a high correlation (r2 = 0.77). Similarly, we obtain good 
                         agreement for CO2 background when comparing our results with those 
                         based on SF6, for the period 2010-2011 when the SF6 measurements 
                         had excellent precision and accuracy. We also found high 
                         correspondence between the methods for background values of CO, 
                         N2O and CH4. Finally, flux estimates based on our new method agree 
                         well with the CO2 flux estimates for 2010 and 2011 estimated using 
                         the SF6-based method. Together, our findings suggest that our 
                         trajectory-based method is a robust new way to derive background 
                         air concentrations for the purpose of greenhouse gas flux 
                         estimation using vertical profile data.",
                  doi = "10.3390/atmos11070734",
                  url = "http://dx.doi.org/10.3390/atmos11070734",
                 issn = "2073-4433",
             language = "en",
           targetfile = "atmosphere-11-00734.pdf",
        urlaccessdate = "28 abr. 2024"
}