A New Approach to estimate GHG content of air entering the Amazon basin for purpose of GHG fluxes using air column budgets
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2017
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INTERNATIONAL CARBON DIOXIDE CONFERENCE, 10th
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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.
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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. A New Approach to estimate GHG content of air entering the Amazon basin for purpose of GHG fluxes using air column budgets. In: INTERNATIONAL CARBON DIOXIDE CONFERENCE, 10th, August 21-25, 2017, Interlaken, Switzerland. Abstract... Bern, Switzerland: Swiss Academy of Sciences (SCNAT), 2017. p. 242-242. Disponível em: http://repositorio.ipen.br/handle/123456789/29150. Acesso em: 12 May 2024.
Esta referência é gerada automaticamente de acordo com as normas do estilo IPEN/SP (ABNT NBR 6023) e recomenda-se uma verificação final e ajustes caso necessário.