10th International Aerosol Conference September 2 - September 7, 2018 America's Center Convention Complex St. Louis, Missouri, USA
Abstract View
The Sahara Desert Dust Contribution in the Central Amazonia Determined with in situ Measurements in the ATTO Tower and in the ZF2 Reserve and Remote Sensing Use
RAYNER SANTOS, Paulo Artaxo, National Institute of Research of the Amazon
Abstract Number: 1683 Working Group: Aerosol Transport and Transformation
Abstract During the wet season, the Amazon receives intense dust emissions from the Sahara desert, which is the largest source of dust in the atmosphere, contributing to changes in climate and atmospheric chemistry at regional and global scales. Sporadically, this dust is accompanied by aerosol of biomass burning from the Sahel region. The Amazon region receives this dust through transatlantic transport, which acts in the long term as a valuable fertilizer in this ecosystem, providing essential nutrients to the forest. This work aims to quantify the aerosols transported to the Amazon from the North of Africa by the trade winds and to investigate the different compositions of the aerosols from continuous and long term measures in three sites in the Central Amazon, in a region of forest to north of the city of Manaus-AM. For the first time, from an extensive and diverse database it was possible to determine the elemental concentration of dust aerosols from the Sahara desert and Black Carbon (BC) of the Sahel, using the proton induction technique as well as X-ray fluorescence by dispersive energy (PIXE and EDXRF) applied to the filters obtained in a region of forest (ZF2), with validation from values present in the atmospheric column using data obtained from two AERONET Network Solar Photometers in the central region of Amazonia, as well as we measured the presence of the aerosols sampled from the influence on absorption and scattering. Products obtained by the NASA-Giovanni system, which provides access to a wide range of remote sensing data from NASA and other data sets, which associated with HYSPLIT transport modeling, provide a source-receiver relationship of the measured aerosols. It was identified that the presence of coarse particulate material is predominant between the second fortnight of January and the month of May, presenting a mean volumetric radius ranging from 1.30 μm to 8.71 μm, and contributes up to 78% of the Optical Depth of Aerosol (AOD 500 nm). The highest prevalence of dust aerosols occurred during this same period, with a concentration of 204,09 ± 604,09 ng/m3, and from 141 pairs of filters, 60 dust-intensive events were identified between 2008 and 2015, representing 85% of all identified dust. The BC has a lower presence in this period and has a concentration of 160.12 ± 158.14 ng/m3. The Ångström parameter was adjusted for the aerosol samples in the Amazon, showing, for dust, Angstrom values of spreading ≤ 1,11 and absorption ≥ 0,87. The relationship between backtrajector analysis and satellite products obtained from the MODIS Terra sensor showed that the origin of air masses coming from regions with high AOD in the Sahara and Sahel region contributed to ZF2. From these results we can conclude that the highest frequency of dust deposition during the wet season occurs between mid-January and May and its dry deposition represents 6.09% of the total aerosol mass measured in the period, and this deposition strongly impacts the coefficients of absorption and scattering of radiation.