LUCAS GATTI DOMINGUES

LUCAS GATTI DOMINGUES

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A new background method for greenhouse gases flux calculation based in back-trajectories over the Amazon
2020 - DOMINGUES, LUCAS G.; GATTI, LUCIANA V.; AQUINO, AFONSO; SÁNCHEZ, ALBER; CORREIA, CAIO; GLOOR, MANUEL; PETERS, WOUTER; MILLER, JOHN; TURNBULL, JOCELYN; SANTANA, RICARDO; MARANI, LUCIANO; CÂMARA, GILBERTO; NEVES, RAIANE; CRISPIM, STÉPHANE
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.
A New Approach to estimate GHG content of air entering the Amazon basin for purpose of GHG fluxes using air column budgets
2017 - GATTI, LUCIANA V.; DOMINGUES, LUCAS G.; CORREIA, CAIO S.C.; SANCHEZ, ALBER; GLOOR, MANUEL; MILLER, JOHN B.; ALDEN, CAROLINE; MARANI, LUCIANO; SANTOS, RICARDO S.; COSTA, WELLISON R.; CRISPIM, STEPHANE P.; BORGES, VIVIANE F.; AQUINO, AFONSO R.
Amazon humid forests are an important part of the tropical climate system and are a large pool of organic carbon which can be released rapidly both as a result of human destruction as well possibly in response to changing climate. In 2000 we started to measure regularly vertical profiles over the Brazilian Amazon Basin to estimate GHG balances as a large scale diagnostic of longer-term changes and short term responses to climate anomalies. To estimate Amazon Basin regional fluxes based on vertical profile data, we use an air column budget technique. To do so we profit from the primary air flow pattern over the basin with trade winds entering the basin along the North-east Atlantic coast, then travelling westwards towards the Andes, from where the air flow is bent south-eats-wards returning back towards the sea. Thus we can estimate fluxes from the difference in air column greenhouse gas content at a site in the Amazon basin and the air column content of air entering the basin, and an estimate of the time it takes for air parcels to travel from the Atlantic coast to the site in the Amazon. To estimate travel time we use back-trajectories calculated based on meteorological fields [Hysplit1 GDAS 1degree] One approach to estimate the greenhouse gas air column content of air entering the basin is to express air entering the basin as a mixture of northern hemisphere and southern hemisphere air. Specifically we use as end-members air concentrations measured at Barbados (RPB, NOAA site) and Ascension (ASC, NOAA site) respectively. To estimate fractional contributions we use a linear mixing model expressing in situ measured SF6 as a weighted sum of SF6 measured at the two NOAA background sites. Because flux estimates are very sensitive to SF6 precision and accuracy we have developed an alternative approach. Instead of determining weights from SF6 we base the weights on the latitude where a back-trajectory extending backwards in time from the site intersects a line connecting RPB, ASC (until 30°S). Now we use RPB, ASC and CPT (Cape Point; 34.35°S, 18.49°E). We will describe in detail the method and show tests of the approach using the SF6 based method which we trust for the years 2010 and 2011, but less for the following years because the NOAA quantification method change and our continue during more 4 years in the old linear quantification method. This difference produce slightly bias over time. While we developed this method for the Amazon it similarly could be applied to other regions with clearly defined wind patterns.
Amazon Basin biomass burning emission and its correlation with climatology and deforestation
2017 - DOMINGUES, LUCAS G.; GATTI, LUCIANA V.; GLOOR, MANUEL; MILLER, JOHN B.; AQUINO, AFONSO R.; ARAGAO, LUIZ E.O. e C.; ANDERSON, LIANA O.; MARANI, LUCIANO; CORREIA, CAIO S. de C.; SILVA, MARCELO G.; BORGES, VIVIANE F.; IPIA, ALBER H.S.; BASSO, LUANA S.; SANTOS, RICARDO S.; CRISPIM, STEPHANI P.; COSTA, WELLISON R.
Tropical rainforests have great potential to affect the global carbon budget considering their large quantities of labile carbon stored in forests and soils. Among the tropical regions, the Amazon forest covers the largest area and also hosts the largest carbon pool (~200 PgC), corresponding for 50% of its biome globally. It has a total area of approximately 6.7 million km2, of which, 4.2 million km2 is in Brazil, which corresponds to approximately 60 % of Amazon territory, and contains one quarter of global biodiversity. Over recent years, the Amazon Basin hydrological cycle has changed considerably which presented severe droughts in 2005, 2010 and 2015. 2015 is likely the largest drought over the past 15 years. Droughts in the Amazon are intrinsically correlated to extensive wildfires. At 2004/2005 the number of fire hot spots reached its maximum, coincident with the peak in deforestation. However, in the recent years, despite the decrease in deforestation rates, increase in fire hot spots have been observed, particularly during the years of extreme drought, 2010 and 2015. 2011 had the fewest number of fire hot spots, but since 2013 a positive trend was identified, reaching the maximum peak in 2015. Although deforestation estimation has decreased strongly over the last decade (71% reduction from 2004 to 2012), estimates of fire related carbon fluxes to the atmosphere estimated using regular atmospheric carbon monoxide concentration measurements indicate that there may be a discrepancy. These data do suggest a much smaller decrease, which lead us to believe that deforestation, as observed from satellite, is not the only process causing release of carbon by fires. Thus, understanding the relation between carbon emissions from biomass burning and climate, fire hot spots based on remote sensing and deforestation is important as it may reveal biases in remote sensing based estimates of deforestation. In turn it may help to evaluate the effectiveness of actions to preserve the forests. To elucidate the actual contribution and the carbon emission from biomass burning in the Amazon Basin, measurements of carbon monoxide are an important tool. We will report the results from a recently established pan Amazon lower troposphere biweekly to monthly atmospheric sampling program for the years 2010 to 2014. Amazon Basin biomass burning carbon emissions have been determined by applying a mass balance technique to carbon monoxide measured from vertical profiles in four sites over the Amazon Basin. We will present these results from biomass burning and compare the carbon monoxide emissions with those from carbon dioxide, resulting in a ratio of carbon biomass burning emission which we will analyze with respect to climate, deforestation and number of fire hot spots.
Amazon basin and brazilian coast SF6 study in a 15 years time series
2017 - SANTOS, R.S.; GATTI, L.V.; DOMINGUES, L.G.; CORREIA, C.S.C.; AQUINO, A.R.; BASSO, L.S.; BORGES, V.F.; COSTA, W.R.; CRISPIM, S.P.; MARANI, L.; GLOOR, E.U.; MILLER, J.B.; PETERS, W.
The sulphur hexafluoride (SF6) is known as a potent Long Lived Greenhouse Gases and it is a synthetic gas with a millennia lifetime, about 3200 years, and has a Global Warm Potential 23000 time higher than the Carbon Dioxide (CO2). Levin et al. (2010)1 showed that SF6 emissions decreased after 1995, most likely because of emissions reductions in developed countries, but then increased after 1998. It is produced by the chemical industry, mainly as an electrical insulator in power distribution equipment2. Due its very long lifetime, SF6 emissions are accumulating in the atmosphere. Its global mole fraction increased nearly linearly in recent decades and in 2014 is about twice the level observed in the mid-1990s3. Its concentration was 4.2 parts per trillion (ppt) in 1998 (TAR) and has continued to increase linearly over the past decade, implying that emissions are approximately constant. Because of these characteristics, the SF6 has been as an essentially inert tracer to study atmospheric and oceanic transport processes3. The Amazon Basin is an ecosystem that has a growing interest by researchers around the world because of its role at the Climate Change. The emissions of SF6 in the Amazon Basin are considered non existents and, a time series of 15 years has the potential to show the behaviour of this gas in a large area. Until now, our mainly interest in SF6 concentrations is to use this gas as a transport tracer to calculate the BKG to Amazon and determinate the CO2, CH4 and N2O fluxes over the Amazon Basin. SF6 atmospheric measurements were started with vertical profiles using small aircrafts, since 2000 in Santarém (SAN; 2.86ºS; 54.95ºW), 2009 in Rio Branco (RBA; 9.38ºS, 67.62ºW), 2010 in Alta Floresta (ALF; 8.80ºS, 56.75ºW)and Tabatinga (TAB; 5.96ºS, 70.06ºW), all these sites located in Brazilian Amazon Basin. Since 2010, we started flasks measurements at two sites located at the Brazilian Atlantic coast: in Salinópolis (SAL; 0.60°S, 47.37°W) and in Natal (NAT; 5.48°S, 35.26°W) and later in 2014 at Camocim (CAM; 2.86°S, 40.08°W) and in 2016 at Itarema in a 100m tower (ITA; 2.93°S, 39.84°W). This work will present analyse of 15 years SF6 measurements at the Amazon Basin and Brazilian coast show the trends, comparing the years and the behaviour among the sites regions which is expect to change mainly by the differences of the air masses origin.
Carbon monoxide measurements as a biomass burning tracer at the amazon basin
2017 - DOMINGUES, L.G.; GATTI, L.V.; GLOOR, M.; MILLER, J.; AQUINO, A.R.; MARANI, L.; CORREA, C.S.C.; BORGES, V.F.; SANTOS, R.S.; CRISPIM, S.P.; SANCHES, A.; COSTA, W.R. da
The tropical rainforests have an amount of carbon stored into its plants and soil comparable to half of the amount of atmospheric carbon contained at the atmosphere before the start of industrialization at the 18th century. Among the tropical regions, the Amazon forest covers the largest area and also hosts the largest carbon pool (~200 PgC), corresponding for 50% of its biome globally (1) . Considering the capability of rapid release and the amount of storage carbon, there are surprisingly few studies of emission ratios (2) and, in order to elucidate the actual contribution and the carbon emission from biomass burning in the Amazon Basin, measurements of carbon monoxide are an important tool. We will report results of a pan-Amazon low troposphere program used small airplanes, in 7 study sites from 2000 to 2016. The aircraft measurement program was started in 2000 with monthly/biweekly vertical profile sampling at SAN (2.86S 54.95W). From December 2004 to December 2007 we performed vertical profiles at MAN (Dec 2004 / Dec 2007). In 2010, a new step in our program was started. We added three more aircraft sites: TAB (5.96S 70.06W), RBA (9.38S 67.62W) and ALF (8.80S 56.75W). In 2013 TAB site was moved to TEF (3.39S 65.6W) and we add two more aircraft sites with vertical profiles from 300m to 7300 m, at Salinópolis (SAH 0.60S; 47,37W) near the Atlantic coast and RBH at the same place then RBA, in the western Amazon. The Amazon Basin biomass burning carbon emissions have been determined by applying a mass balance technique to carbon monoxide (CO) measured from vertical profiles in sites over the Amazon Basin, which is compared with carbon dioxide (CO2) emission when it is a clear biomass-burning plume in the vertical profile (3). We will present these CO results that is related to biomass burning and compare the carbon monoxide emissions with those from carbon dioxide, resulting in a ratio of carbon biomass burning emission which we will analyse with respect to climate, deforestation and number of fire hot spots.